The descending thoracic aorta begins at the lower border of T4 near the midline as a continuation of the arch of the aorta. It descends and ends at the level of T12 at the aortic hiatus in the diaphragm, where it becomes the abdominal aorta.

The aorta gives off the following branches: (descending order)

1. Bronchial arteries
2. Mediastinal arteries
3. Oesophageal arteries
4. Pericardial arteries
5. Superior phrenic arteries

The posterior intercostal arteries are branches that originate throughout the length of the posterior aspect of the descending thoracic aorta.

The inferior thyroid artery is usually derived from the thyrocervical trunk, a branch of the subclavian artery.

Once the decision to deliver a baby by caesarean section has been made, it should be carried out with a level of urgency commensurate with the risk to the baby and the mother’s safety.

There are four types of caesarean section urgency:

Category 1 – Endangering the life of the mother or the foetus
Category 2 – Maternal or foetal compromise that is not immediately life threatening
Category 3 – Early delivery is required, but there is no risk to the mother or the foetus.
Category 4: Elective delivery at a time that is convenient for both the mother and the maternity staff.

Caesarean sections for categories 1 and 2 should be performed as soon as possible after the decision is made, especially for category 1. For category 1 caesarean sections, a decision to deliver time of 30 minutes is currently used.

In most cases, Category 2 caesarean sections should be performed within 75 minutes of making the decision.

The condition of the woman and the unborn baby should be considered when making a decision for a quick delivery, as it may be harmful in some cases.

There is no evidence of foetal compromise in the example above (early foetal pulse decelerations and a pH of less than 7.25). Early foetal pulse decelerations are most likely caused by the uterus compressing the foetal head. The foetus is not harmed by these. A spinal anaesthetic is preferred over a general anaesthetic whenever possible.

If the foetal scalp blood pH is greater than 7.25, it’s a good idea to repeat the test later and look for any changes. When a foetus decelerates, the mother should be given oxygen, kept in a left lateral position, and kept hydrated to avoid the need for a caesarean section.

Using a lean body weight metric encompasses a more scientific approach to weight-based dosing. Lean body weight reflects the weight of all ‘non-fat’ body components, including muscle and vascular organs such as the liver and kidneys. As lean body weight contributes to approximately 99% of a drug’s clearance, it is useful for guiding dosing in obesity.

This metric has undergone a number of transformations. The most commonly cited formula derived by Cheymol is not optimal for dosing across body compositions and can even produce a negative result. A new formula has been developed that appears stable across different body sizes, in particular the obese to morbidly obese.

A practical downfall of the calculation of lean body weight (and other body size descriptors) is the numerical complexity, which may not be palatable to a busy clinician. Often limited time is available for prescribing and an immediate calculation is required. Lean body weight calculators are available online, for example in the Therapeutic Guidelines.

Using total body weight assumes that the pharmacokinetics of the drug are linearly scalable from normal-weight patients to those who are obese. This is inaccurate. For example, we cannot assume that a 150 kg patient eliminates a drug twice as fast as a 75 kg patient and therefore double the dose. Clinicians are alert to toxicities with higher doses, for example nephro- and neurotoxicity with some antibiotics and chemotherapeutics, and bleeding with anticoagulants. Arbitrary dose reductions or ‘caps’ are used to avoid these toxicities, but if too low can result in sub-therapeutic exposure and treatment failure.

Body surface area is traditionally used to dose chemotherapeutics. It is a function of weight and height and has been shown to correlate with cardiac output, blood volume and renal function. However, it is controversial in patients at extremes of size because it does not account for varying body compositions. As a consequence, some older drugs such as cyclophosphamide, paclitaxel and doxorubicin were ‘capped’ (commonly at 2 m^2) potentially resulting in sub-therapeutic treatment. Recent guidelines suggest that unless there is a justifiable reason to reduce the dose (e.g. renal disease), total body weight should be used in the calculation of body surface area, until further research is done. Little research into dosing based on body surface area has been conducted for other medicines.

Ideal body weight was developed for insurance purposes not for drug dosing. It is a function of height and gender only and, like body surface area, does not take into account body composition. Using ideal body weight, all patients of the same height and sex would receive the same dose, which is inadequate and generally results in under-dosing. For example a male who has a total body weight of 150 kg and a height of 170 cm will have the same ideal body weight as a male who is 80 kg and 170 cm tall. Both could potentially receive a mg/kg dose based on 65 kg (ideal body weight).

Foramen ovale, ductus arteriosus (DA) and ductus venosus (DV) are the three important cardiac shunts in-utero.

At birth the umbilical vessels constrict in response to stretch as they are clamped. Blood flow through the ductus venosus (DV) decreases but the DV closes passively in 3-10 days.

As the pulmonary circulation is established, there is a drastic fall in pulmonary vascular resistance and an increased pulmonary blood flow. This increases flow and pressure in the Left Atrium that exceeds that of the right atrium. The difference in pressure usually leads to the IMMEDIATE closure of the foramen ovale.

The DA is functionally closed within the first 36-hours of birth in a healthy full-term newborn. Subsequent endothelial and fibroblast proliferation leads to permanent anatomical closure within 2 – 3 weeks.

Oxygenated blood from the placenta passes via the umbilical vein to the liver. Blood also bypasses the liver via the ductus venosus into the inferior vena cava (IVC). The Crista dividens is a tissue flap situated at the junction of the IVC and the right atrium (RA). This flap directs the oxygen-rich blood, along the posterior aspect of the IVC, through the foramen ovale into the left atrium (LA).

The Eustachian valve also known as the valve of The IVC is a remnant of the crista dividens.

Potassium maintains the resting potential of cardiac myocytes, with depolarization triggered by a rapid influx of sodium ions, and repolarization due to efflux of potassium. A slow influx of calcium is responsible for the longer duration of a cardiac action potential compared with skeletal muscle.

The cardiac action potential has several phases which have different mechanisms of action as seen below:

Phase 0: Rapid depolarisation – caused by a rapid sodium influx.
These channels automatically deactivate after a few ms.

Phase 1: caused by early repolarisation and an efflux of potassium.

Phase 2: Plateau – caused by a slow influx of calcium.

Phase 3 – Final repolarisation – caused by an efflux of potassium.

Phase 4 – Restoration of ionic concentrations – The resting potential is restored by Na+/K+ATPase.
There is slow entry of Na+into the cell which decreases the potential difference until the threshold potential is reached. This then triggers a new action potential

Of note, cardiac muscle remains contracted 10-15 times longer than skeletal muscle.

Different sites have different conduction velocities:
1. Atrial conduction – Spreads along ordinary atrial myocardial fibres at 1 m/sec

2. AV node conduction – 0.05 m/sec

3. Ventricular conduction – Purkinje fibres are of large diameter and achieve velocities of 2-4 m/sec, the fastest conduction in the heart. This allows a rapid and coordinated contraction of the ventricles

Cardiac output = stroke volume x heart rate

Left ventricular ejection fraction = (stroke volume / end diastolic LV volume ) x 100%

Stroke volume = end diastolic LV volume – end systolic LV volume

Pulse pressure = Systolic Pressure – Diastolic Pressure

Systemic vascular resistance = mean arterial pressure / cardiac output
Factors that increase pulse pressure include:
-a less compliant aorta (this tends to occur with advancing age)
-increased stroke volume

The external carotid artery has eight important branches:
1. Superior thyroid artery
2. Ascending pharyngeal artery
3. Lingual artery
4. Facial artery
5. Occipital artery
6. Posterior auricular artery
7. Maxillary artery (terminal branch)
8. Superficial temporal artery (terminal branch)

There is no mandibular artery but the first part of the maxillary artery is called the mandibular part as it is posterior to the lateral pterygoid muscle.
The maxillary artery is divided into three portions by its relation to the lateral pterygoid muscle:
first (mandibular) part: posterior to the lateral pterygoid muscle
second (pterygoid or muscular) part: within the lateral pterygoid muscle
third (pterygopalatine) part: anterior to the lateral pterygoid muscle

The vertebral artery originates from the subclavian artery and ascends through the neck in the transverse foramen of the C1-C6 vertebrae. C2 vertebra is called the axis vertebra. A part of the vertebral artery lies in a groove on the upper surface of the atlas’s (C1) posterior arch. It enters the vertebral canal below the inferior border of the posterior atlantooccipital membrane. The vertebral arteries then enter the skull via the foramen magnum.

Understanding of the cardiac action potential helps with the understanding of the ECG which measures the electrical activity of the heart. This is reflected in its waveform.
The rapid depolarisation phase is reflected in the QRS complex. After this phase comes the plateau phase which is represented by the ST segment. Lastly, the T wave shows repolarisation, phase 3.

The cardiac action potential has several phases which have different mechanisms of action as seen below:
Phase 0: Rapid depolarisation – caused by a rapid sodium influx.
These channels automatically deactivate after a few ms

Phase 1: caused by early repolarisation and an efflux of potassium.

Phase 2: Plateau – caused by a slow influx of calcium. (ST segment)

Phase 3 – Final repolarisation – caused by an efflux of potassium. (T wave)

Phase 4 – Restoration of ionic concentrations – The resting potential is restored by Na+/K+ATPase.
There is slow entry of Na+into the cell which decreases the potential difference until the threshold potential is reached. This then triggers a new action potential

Of note, cardiac muscle remains contracted 10-15 times longer than skeletal muscle.

Different sites have different conduction velocities:
1. Atrial conduction – Spreads along ordinary atrial myocardial fibres at 1 m/sec

2. AV node conduction – 0.05 m/sec

3. Ventricular conduction – Purkinje fibres are of large diameter and achieve velocities of 2-4 m/sec, the fastest conduction in the heart. This allows a rapid and coordinated contraction of the ventricles

Phase 0 trials assist the scientists in studying the behaviour of drugs in humans by micro dosing patients. They are used to speed up the developmental process. They have no measurable therapeutic effect and efficiency.

Phase 1 is associated with assessing whether a drug is safe to use or not. The process is extensive and can take up to several months. It also involves healthy participants (less than 100) that are paid to take part in the study. The side effects upon increasing dosage are also addressed by the study. The effects the drug has on humans including how its absorbed, metabolized and excreted are studied. Approximately 70% of the drugs pass this phase.

Phase 2 trials involve patients that are suffering from the disease under study and are associated with determining the efficiency and the optimum dosage of the drug.

Phase 3 also assesses the efficacy but at a higher scale with larger population sample.

Phase 4 trials are involved with the long term effects and side effects of the drug.

Its known that 68.3% of the total values of a normally distributed variable are found within a range of 1 standard deviation from the mean which makes the range to be 4.3 to 4.9 mmol/L.

The neuroleptic malignant syndrome (NMS) is a rare complication in response to neuroleptic or antipsychotic medication.

The main features are:
– Elevated creatinine kinase
– Hyperthermia and tachycardia
– Altered mental state
– Increased white cell count
– Insidious onset over 1-3 days
– Extrapyramidal dysfunction (muscle rigidity, tremor, dystonia)
– Autonomic dysfunction (Labile blood pressure, sweating, salivation, urinary incontinence)

Management is supportive of ICU care, anticholinergic drugs, increasing dopaminergic activity with Amantadine, L-dopa, and dantrolene, and non- depolarising neuromuscular blockade drugs.

Since Olanzapine is a potential cause of NMS it is not a treatment.

The following terms are used in medical testing:

True negative – The test is negative and the patient does not have the disease.
True positive – The test is positive and the patient has the disease.
False positive – The test is positive but the patient does not have the disease.
False negative – The test is negative but the patient has the disease.

The sensitivity of a predictive test = true positives / (true positives + false negatives).

The specificity of a test = true negatives / (false positives + true negatives).

The negative predictive value of a test = true negatives / (false negatives + true negatives).

The Kappa Statistic or Cohen’s Kappa is a statistical measure of inter-rater reliability for categorical variables. It is used when two raters both apply a criterion based on a tool to assess whether or not some condition occur. A good example can be two doctors rating individuals for diabetes occurrence on the basis of symptoms.

It gives a quantitative measure of the magnitude of agreement between observers.

Kappa can take any value between 0 and 1. 0 implies the observers are in complete disagreement and a value of 1 implies complete agreement.

The femoral triangle is a wedge-shaped area found within the superomedial aspect of the anterior thigh. It is a passageway for structures to leave and enter the anterior thigh.

Superior: Inguinal ligament
Medial: Adductor longus
Lateral: Sartorius
Floor: Iliopsoas, adductor longus and pectineus

The contents include: (medial to lateral)
Femoral vein
Femoral artery-pulse palpated at the mid inguinal point
Femoral nerve
Deep and superficial inguinal lymph nodes
Lateral cutaneous nerve
Great saphenous vein
Femoral branch of the genitofemoral nerve

Drugs cross the placenta by Simple, Ion channel and Facilitated diffusion; Exocytosis and Endocytosis, Osmosis, and Active transport (primary and secondary)

The following factors influence rate of diffusion across the placenta:

Protein binding
Degree of ionisation
Placental blood flow
Maternal and foetal blood pH
Materno-foetal concentration gradient.
Thickness of placental membrane
Molecular weight of drug <600 Daltons cross by diffusion
Lipid solubility (lipid soluble molecules readily diffuse across the placenta)

Rocuronium has a F/M ratios of 0.16, a 30% plasma protein binding, low lipid solubility, a low volume of distribution (0.25L/kg), and a high molecular weight (530Da).

With respect to oxygen transport in cells, almost all oxygen is transported within erythrocytes. There is limited solubility and only 1% is carried as solution. Thus, the amount of oxygen transported depends upon haemoglobin concentration and its degree of saturation.

Haemoglobin is a globular protein composed of 4 subunits. Haem is made up of a protoporphyrin ring surrounding an iron atom in its ferrous state. The iron can form two additional bonds – one is with oxygen and the other with a polypeptide chain.
There are two alpha and two beta subunits to this polypeptide chain in an adult and together these form globin. Globin cannot bind oxygen but can bind to CO2 and hydrogen ions.
The beta chains are able to bind to 2,3 diphosphoglycerate. The oxygenation of haemoglobin is a reversible reaction. The molecular shape of haemoglobin is such that binding of one oxygen molecule facilitates the binding of subsequent molecules.

The oxygen dissociation curve (ODC) describes the relationship between the percentage of saturated haemoglobin and partial pressure of oxygen in the blood.
Of note, it is not affected by haemoglobin concentration.

Chronic anaemia causes 2, 3 DPG levels to increase, hence shifting the curve to the right

Haldane effect – Causes the ODC to shift to the left. For a given oxygen tension there is increased saturation of Hb with oxygen i.e. Decreased oxygen delivery to tissues.
This can be caused by:
-HbF, methaemoglobin, carboxyhaemoglobin
-low [H+] (alkali)
-low pCO2
-ow 2,3-DPG
-ow temperature

Bohr effect – causes the ODC to shifts to the right = for given oxygen tension there is reduced saturation of Hb with oxygen i.e. Enhanced oxygen delivery to tissues. This can be caused by:
– raised [H+] (acidic)
– raised pCO2
-raised 2,3-DPG
-raised temperature

Adequate humidification is vital to maintain homeostasis of the airway. Heat and moisture exchangers conserve some of the exhaled water, heat and return them to inspired gases. Many heat and moisture exchangers also perform bacterial/viral filtration and prevent inhalation of small particles. Heat and moisture exchangers are also called condenser humidifier, artificial nose, etc. Most of them are disposable devices with exchanging medium enclosed in a plastic housing. For adult and paediatric age group different dead space types are available. Heat and moisture exchangers are helpful during anaesthesia and ventilatory breathing system. To reduce the damage of the upper respiratory tract through cooling and dehydration inspiratory air can be heated and humidified, thus preventing the serious complications. Moreover, they are the most appropriate humidification devices used for routine anaesthesia.

Gases can be bubbled through water to increase humidity. Passing gas through water at room temperature causes the gas to cool due to latent heat of vaporisation. The water bath can be heated. This improves the efficiency of the device and also reduces the incidence of bacterial colonisation.

Nebulisers use a venturi system which employs the Bernoulli effect. A gas at high flow passes through a constriction causing the gas to accelerate, reducing its potential energy allowing other gases or liquids to be entrained. This can include medications or in the case of humidification, water vapour. The size of the water droplet produced by nebulisation determines where in the airway it is deposited. Standard nebulisers produced droplets of 4 microns in diameter and these are deposited in the upper airway and trachea. Efficacy can be improved by passing the droplets over an anvil which further reduces particle size. The most efficient form of nebuliser is the ultrasonic nebuliser. Here a transducer immersed in water and vibrated at a frequency of 3MHz produces1-2micron droplets. These particles easily reach the bronchioles and provide excellent humidification.

The response of cerebral blood flow (CBF) to hyperoxia (PaO2 >15 kPa, 113 mmHg), the cerebral oxygen vasoreactivity is less well defined. A study originally described, using a nitrous oxide washout technique, a reduction in CBF of 13% and a moderate increase in cerebrovascular resistance in subjects inhaling 85-100% oxygen. Subsequent human studies, using a variety of differing methods, have also shown CBF reductions with hyperoxia, although the reported extent of this change is variable. Another study assessed how supra-atmospheric pressures influenced CBF, as estimated by changes in middle cerebral artery flow velocity (MCAFV) in healthy individuals. Atmospheric pressure alone had no effect on MCAFV if PaO2 was kept constant. Increases in PaO2 did lead to a significant reduction in MCAFV; however, there were no further reductions in MCAFV when oxygen was increased from 100% at 1 atmosphere of pressure to 100% oxygen at 2 atmospheres of pressure. This suggests that the ability of cerebral vasculature to constrict in response to increasing partial pressure of oxygen is limited.

Increases in arterial blood CO2 tension (PaCO2) elicit marked cerebral vasodilation.

CBF increases with general anaesthesia, ketamine anaesthesia, and hypoviscosity.

The operating theatre is an unusual place with several applications of electrical equipment to the human body. This can lead to potential dangers associated with it that need to be prevented. Electrical safety in the operation theatre is the understanding of how these potential dangers can occur and how they can be prevented.

Electricity can cause morbidity or mortality by one of the following ways:
(i) electrocution
(ii) burns
(iii) ignition of a flammable material, causing a fire or explosion.

Electrocution is dependant on factors like duration of contact with electric current, the current pathway and the frequency and size of current.

Option A: The higher the frequency, the less effects of electrocution on the body.

Option B & D: Equipment can be classified in classes and types.
The class designation describes the method used for protection against electrocution. Class I is basic protection, class II is double insulation and class III is safety extra low voltage.
The type designation describes the degree of protection based on the maximum permissible leakage currents under normal and fault conditions.
Type B:
can be class I, II or III but the maximum leakage current must not exceed 100 µA. It is therefore not suitable for direct connection to the heart.
Type BF
Similar to type B, but uses an isolated (or floating) circuit.
Type CF
Only type CF protect against microshock as they allow leakage currents of 0.05 mA per electrode for class I and 0.01 mA for class II. Microshock is a small leakage current that can cause harm because of direct connection to the heart via transvenous lines or wires, bypassing the impedance of the skin, leading to ventricular fibrillation. Microshock current of 100 ?A is sufficient to cause VF.

Option C: A 75mA electrocution can cause ventricular fibrillation. Use the following as a general guide to understand the effect of current size on the body.
1 mA – tingling pain
5 mA – pain
15 mA – tonic muscular contraction
50 mA – respiratory muscle paralysis
75 mA – ventricular fibrillation.

Option E: Wet skin reduces the resistance to current flow and therefore increases the effects of electrocution.

The total body water content of a 70kg man is (70 × 0.6) = 42 litres. For a woman, the calculation is (70 × 0.55) = 38.5 litres.

For a man, it is subdivided into:

Extracellular fluid (ECF) = 14L (1/3)
Intracellular fluid (ICF) = 28L (2/3).

The ECF volume is further divided into:

Interstitial fluid = 10.5 litres
Plasma = 3 litres
Transcellular fluid (CSF/synovial fluid) = 0.5 litres.

Directly measured fluid compartments:

Heavy water (deuterium) can be used to measure total body water content, which is freely distributed.
Albumin labelled with a radioactive isotope or using a dye called Evans blue can be used to measure Plasma volume . They do not diffuse into red blood cells.
Radiolabelled (Cr-51) red blood cells can be used to measure total erythrocyte volume.
Inulin as the tracer can be used to measure ECF volume as it circulate freely in the interstitial and plasma volumes.

Indirectly measured fluid compartments:

Total blood volume can be calculated with the level of haematocrit and the volume of total circulating red blood cells.
ICF volume can be calculated by subtracting ECF volume from total blood volume.

Maintenance therapy aims to replace water and electrolytes lost under ordinary conditions. In the perioperative period, maintenance fluid administration may not sufficiently account for the increased fluid requirements caused by third-space losses into the interstitium and gut. Specific recommendations vary with the patient, the procedure, and the type and amount of fluid administered during the operation. The fluid for maintenance therapy replaces deficits arising primarily from insensible losses and urinary or gastrointestinal (GI) losses.

The maintenance fluid volume can be computed using the Holliday-Segar method.

Body weight Fluid volume
first 10 kg 4 ml/kg/hr
next 10-20 kg 2 ml/kg/hr
>20 kg 1 ml/kg/hr

In the past few years, there has been growing recognition of the increased risk of hyponatremia in hospitalized children in intensive care and postoperative settings who receive hypotonic maintenance fluids. Several studies, including a randomized controlled trial and a Cochrane analysis, found that the use of isotonic fluids is associated with fewer electrolyte derangements and concluded that isotonic maintenance fluids are preferable to hypotonic solutions in hospitalized children.

A European consensus statement suggests that an intraoperative fluid should have an osmolarity close to the physiologic range in children in order to avoid hyponatremia, an addition of 1-2.5% in order to avoid hypoglycaemia, lipolysis or hyperglycaemia and should also include metabolic anions as bicarbonate precursors to prevent hyperchloremic acidosis.

A rate of 40 ml/hr is suboptimal.

If 0.9% NaCl with 0% glucose is given at a rate of 65 ml/hr, despite of the correct infusion rate, large volumes can lead to hyperchloremic acidosis.

If 0.18% NaCl with 4% glucose is given at a rate of 65 ml/hr, infusion of this fluid regimen can lead to hyponatremia because of its hypotonicity.

Omitted variable bias occurs when a statistician passes over one or more relevant variables from the study.

Publication bias occurs in publish academic research. it occurs when the results of the study effect the decision whether to publish or not.

Expectation bias occurs when the expectation of a researcher about the results effect the behaviour of the participants. Expectations may come from communication and experiences.

Work up bias occurs in the study of diagnostic test validity, whether a gold standard procedure has been used. work up bias can seriously affect the specificity of the test.

Recall bias introduced when participants in a study are systematically more or less likely to recall and relate information on exposure depending on their outcome status. Recall bias is more potential for Case-control studies.

Marsh (adult) model, when used with children caused over-estimation of plasma concentration. To address this issue Kataria et al developed a three-compartmental model for propofol in children. The pharmacokinetic models used by Target controlled infusion (TCI) systems are used to calculate the relative sizes of the central (vascular), vessel-rich peripheral, and vessel-poor peripheral compartments. The relative volumes of these compartments are different in young children when compared to adults.

Kataria, therefore, is the correct option as described above.

The Maitre model is a three-compartmental model for alfentanil TCI.

The Marsh model describes a propofol TCI model for adults

The Minto model applies to TCI remifentanil.

The Schnider model is also an adult model for propofol that incorporates age and lean body mass as covariates.

The axillary nerve arises from spinal roots C5-C6. It has both sensory and motor functions:

Sensory: Provides innervation to the skin over the lower deltoid area

Motor: Provides innervation to the teres minor (responsible for stabilisation of glenohumeral joint and external rotation of shoulder joint) and deltoid muscles (responsible for abduction of arms glenohumeral joint).

Injury to the axillary nerve will result in the patient being unable to abduct the arm beyond 15 degrees and a loss of sensory feeling over lower deltoid area.

These symptoms could also be a result of over-abduction of the arm (>90°) which would cause the head of the humerus to become dislocated.

When drugs are bound to proteins, drugs cannot cross membranes and exert their effect. Only the free (unbound) drug can be absorbed, distributed, metabolized, excreted and exert pharmacologic effect. Thus, when amide local anaesthetics are bound to ?1-glycoproteins, their duration of action are reduced.

The potency of local anaesthetics are affected by lipid solubility. Solubility influences the concentration of the drug in the extracellular fluid surrounding blood vessels. The brain, which is high in lipid content, will dissolve high concentration of lipid soluble drugs. When drugs are non-ionized and non-polarized, they are more lipid-soluble and undergo more extensive distribution. Hence allowing these drugs to penetrate the membrane of the target cells and exert their effect.

Tissue pKa and pH will determine the degree of ionization.

Body fluid compartments in a 70kg male:
Total volume=42L (60% body weight)
Intracellular fluid compartment (ICF) =28L
Extracellular fluid compartment (ECF) = 14L

ECF comprises:
Intravascular fluid (plasma) = 3L
Extravascular fluid = 11L

Extravascular fluids comprises:
Interstitial fluid = 10.5L
Transcellular fluid = 0.5L

Awareness during general anaesthesia is a frightening experience, which may result in serious emotional injury and post-traumatic stress disorder.

The incidence of awareness during general anaesthesia with current anaesthetic agents and techniques has been reported as 0.2-0.4% in nonobstetric and noncardiac surgery, as 0.4% during caesarean section, and as 1.5% in cardiac surgery.

The incidence during major trauma surgery is higher. Incidence of recall has been reported to be as high as 11-43% in major trauma cases.

The most important determinant of preoxygenation adequacy is expired fraction of oxygen. Denitrogenating of the functional residual capacity is the purpose of preoxygenation. This is dependent on three vital factors: (1) respiratory rate; (2) inspired volume, and; (3) inspired oxygen concentration (FiO2).

Arterial oxygen saturation does not efficiently determine adequacy of preoxygenation because of its inability to measure tissue reserves. Arterial partial pressure of oxygen is also unsuitable for determining preoxygenation adequacy. Moreover, the absence of central cyanosis is a very crude sign of low tissue oxygenation.

The guidelines for the management of cardiac arrest in hypothermic patients published by the UK Resuscitation Council differ slightly from the standard algorithm.

In a patient with a core temperature of less than 30°C, do the following:

If you’re on the shockable side of the algorithm (VF/VT), you should give three DC shocks.
Further shocks are not recommended until the patient has been rewarmed to a temperature of more than 30°C because the rhythm is refractory and unlikely to change.
There should be no drugs given because they will be ineffective.

In a patient with a core temperature of 30°C to 35°C, do the following:

DC shocks are used as usual.
Because they are metabolised much more slowly, the time between drug doses should be doubled.

Active rewarming and protection against hyperthermia should be given to the patient.

Option e is false because there is insufficient information to determine whether resuscitation should be stopped.

Blood vessels (except capillaries and venules) have three distinctive layers (innermost to outermost):
1. Tunica intima
2. Tunica media
3. Tunica adventitia

The tunica media contains smooth muscle cells and is separated from the intima layer by the internal elastic lamina and the adventitia by the external elastic lamina.

ANOVA is based upon within group variance (i.e. the variance of the mean of a sample) and between group variance (i.e. the variance between means of different samples). The test works by finding out the ratio of the two variances mentioned above. (Commonly known as F statistic).

The spinous process is the part of a vertebrae that is directed posteriorly.

Typical cervical vertebra have spinous processes that are small and bifid, except for C7, which has a long and prominent spinous process.

Randomisation can be used to provide control over the confounding variables during the design stage of a study however during analytical stage a technique called stratification is used for controlling confounding variables. Since the question asks for the information that is factually incorrect.

Krebs’ cycle (tricarboxylic acid cycle or citric acid cycle) is a sequence of reactions to release stored energy through oxidation of acetyl coenzyme A (acetyl-CoA). Some of the products are carbon dioxide and hydrogen atoms.

The sequence of reactions, known collectively as oxidative phosphorylation, only occurs in the mitochondria (not cytoplasm).

The Krebs cycle can only take place when oxygen is present, though it does not require oxygen directly, because it relies on the by-products from the electron transport chain, which requires oxygen. It is therefore considered an aerobic process. It is the common pathway for the oxidation of carbohydrate, fat and some amino acids, required for the formation of adenosine triphosphate (ATP).

Pyruvate enters the mitochondria and is converted into acetyl-CoA. Acetyl-CoA is then condensed with oxaloacetate, to form citrate which is a six carbon molecule. Citrate is subsequently converted into isocitrate, alpha-ketoglutarate, succinyl-CoA, succinate, fumarate, malate and finally oxaloacetate.

The only five carbon molecule in the cycle is Alpha-ketoglutarate.

Mesenteric ischemia is ischemia of the blood vessels of the intestines. It can be life-threatening especially if the small intestine is involved.

A critical factor for survival of acute mesenteric ischemia is early diagnosis and intervention. Angiography uses X-ray and contrast dye to image arteries and identify the severity of ischemia or obstruction.

The celiac axis is the first branch of the abdominal aorta and supplies the entire foregut (mouth to the major duodenal papilla). It arises at the level of vertebra T12. It has three major branches:
1. Left gastric
2. Common hepatic
3. Splenic arteries

There are some important landmarks of vessels at different levels of vertebrae that need to be memorized.

T12 – Coeliac trunk

L1 – Left renal artery

L2 – Testicular or ovarian arteries

L3 – Inferior mesenteric artery

L4 – Bifurcation of the abdominal aorta

Magnesium is a very important cation due to its various physiological roles in the body. This includes:
– playing the role of a cofactor in many enzymatic reactions
– influencing hormone receptor binding
– affecting calcium channels
– impact on cardiac, vascular and neural cells

Magnesium sulphate is used as first line in the treatment of eclampsia. Moreover, it has some preventive role in patients with severe pre-eclampsia. All the clinical effects of magnesium are in line with its plasma concentration.

The first sign of magnesium toxicity in obstetric patients is the loss of patellar reflex, which is regularly monitored during treatment. The other options are all late signs of magnesium toxicity.

Whenever there is a doubt, serum magnesium levels should always be monitored.

The table below correlates the effects of increased levels of magnesium on the body:

Plasma Concentration
(mmol/L) Effect
0.7-1.2 Normal
4-8 Decreased deep tendon reflexes, nausea, headache, weakness, malaise, lethargy and facial flushing
5-10 ECG changes (prolonged PR, prolonged QT, and widened QRS)
10 Muscle weakness, loss of deep tendon reflexes, hypotension
15 SA/AV nodal block, respiratory paralysis and depression
20 Cardiac arrest

Classification of hemorrhagic shock according to Advanced Trauma Life Support is as follows:

– Class I haemorrhage (blood loss up to 15%) in which there is no change in blood pressure, RR, or pulse pressure.

– Class II haemorrhage (15-30% blood volume loss) where there is tachycardia, tachypnoea, and a decrease in pulse pressure.

– Class III haemorrhage (30-40% blood volume loss) where clinical signs of inadequate perfusion, marked tachycardia, tachypnoea, significant changes in mental state, and measurable fall in systolic pressure is seen. It almost always requires a blood transfusion.

– Class IV haemorrhage (> 40% blood volume loss) in which marked tachycardia, significant depression in systolic pressure and very narrow pulse pressure, and markedly depressed mental state with cold and pale skin are seen.

Loss of >50% results in loss of consciousness, pulse, and blood pressure.

This patient has been shifted to a sulfonylurea drug whose most common side effect is hypoglycaemia. Similar symptoms can arise in a patient on insulin too. The signs and symptoms are consistent with a hypoglycaemic attack and include tachycardia, altered consciousness, and behaviour. This needs to be treated as an emergency with rapid correction of the blood glucose level using glucose or IV 20% dextrose.

In a hypoglycaemic attack, the body undergoes stress and releases hormones to increase blood glucose levels. These include:
Glucagon
Cortisol
Adrenaline

Adrenaline or epinephrine is the hormone responsible for this patient’s condition and is primarily produced in the medulla of the adrenal gland. It functions primarily to raise cardiac output and raise blood glucose levels in the blood.

Alpha-cells of the islets of Langerhans produce the hormone glucagon, which has opposing effects to insulin.

Follicular cells of the thyroid gland produce and secrete thyroid hormones. Thyroid hormones can cause similar symptoms, but it is unlikely with the patient’s medical history.

Post-ganglionic neurons of the sympathetic nervous system use norepinephrine as a neurotransmitter. Adrenaline can be made in these cells, but it is not their primary production site.

Zona fasciculata of the adrenal cortex is the main site for the production of cortisol.

Opioid receptors are a large family of seven transmembrane domain receptors. They are of four types:

1) Delta opioid receptor

2) Mu opioid receptor

3) Kappa opioid receptor

4) Orphan receptor-like 1

They contain about 372-400 amino acids and thus their molecular weight is different.

Opioid receptor activation reduces the intracellular cAMP formation and opens K+ channels (mainly through µ and δ receptors) or suppresses voltage-gated N-type Ca2+ channels (mainly κ receptor). These actions result in neuronal hyperpolarization and reduced availability of intracellular Ca2+ which results in decreased neurotransmitter release by cerebral, spinal, and myenteric neurons (e.g. glutamate from primary nociceptive afferents).

However, other mechanisms and second messengers may also be involved, particularly in the long-term

According to the 2015 National Institute for Health and Care Excellence (NICE) Guidelines, antibiotic prophylaxis against infective endocarditis (IE) is not recommended routinely for people with any cardiac defect (corrected or uncorrected) due to lack of sufficient evidence regarding its benefits. Instead, antibiotic prophylaxis is recommended for those who are at risk of developing IE, such as those with acquired valvular heart disease with stenosis or regurgitation; hypertrophic cardiomyopathy; valve replacement; and previous IE.

The taeniae coli are the three outer muscular bands of the cecum, ascending colon, transverse colon, and descending colon.

The taeniae coli converge at the base of the appendix in the cecum where they form a complete longitudinal layer. In the ascending and descending colon, the bands are located anteriorly, posteromedially, and posterolateral.

Based on the laboratory reports, the patient is suffering from significant hyponatremia. The symptoms of hyponatremia are mainly neurological and depend on the severity and rapidity of onset of hyponatremia.

Patient symptom according to the hyponatremia level is correlated below:

125 – 130mmol/L – Nausea and malaise
115 – 125mmol/L – Headache, lethargy, seizures, and coma
<120mmol/L - Up to 11% present with coma.

Salmeterol is a long-acting Beta 2 selective agonist. Therefore it is only used for prophylaxis whereas salbutamol is a short-acting Beta 2 agonist and is thus used for the treatment of acute attacks of asthma.

Salmeterol is 15 times more potent than salbutamol at the Beta 2 receptor but 4 times less potent at the Beta 1 receptor.

Tachyphylaxis to the unwanted side effects commonly occurs, but not to bronchodilation.

Impaired ventricular relaxation reduces diastolic filling and therefore preload.

Decreased blood volume decreases preload due to reduced venous return.

Heart failure is characterized by reduced ejection fraction and therefore stroke volume.

Cardiac output = stroke volume x heart rate

Left ventricular ejection fraction = (stroke volume / end diastolic LV volume ) x 100%

Stroke volume = end diastolic LV volume – end systolic LV volume

Pulse pressure (is increased by stroke volume) = Systolic Pressure – Diastolic Pressure

Systemic vascular resistance = mean arterial pressure / cardiac output
Factors that increase pulse pressure include:
-a less compliant aorta (this tends to occur with advancing age)
-increased stroke volume
Aortic stenosis would decrease stroke volume as end systolic volume would increase.
This is because of an increase in afterload, an increase in resistance that the heart must pump against due to a hard stenotic valve.

The left subclavian artery originates from the aortic arch, while the right subclavian artery originates from the brachiocephalic artery.

The subclavian artery gives off branches on both sides of the body:
1. Vertebral artery
2. Internal thoracic artery
3. Thyrocervical trunk
4. Costocervical trunk
5. Dorsal scapular artery

The superior thyroid artery is the first branch of the external carotid artery. The other branches of the external carotid artery are:
1. Superior thyroid artery
2. Ascending pharyngeal artery
3. Lingual artery
4. Facial artery
5. Occipital artery
6. Posterior auricular artery
7. Maxillary artery
8. Superficial temporal artery

The tenth cranial nerve (vagus nerve) has both sensory and motor divisions.

It emerges from the anterolateral surface of the medulla in a groove between the olive and the inferior cerebellar peduncle as a series of 8-10 rootlets . It leaves the skull through the middle compartment of the jugular foramen and descends within the carotid sheath between the internal carotid artery and internal jugular vein. The right vagus crosses in front of the first part of the subclavian artery. It gives off the right recurrent laryngeal nerve at this point.

The left recurrent laryngeal nerve passes around the ligamentum arteriosum.

The external laryngeal nerve supplies the cricothyroid muscle while the recurrent laryngeal nerve supplies the other laryngeal muscles.

The cranial part of the accessory nerve supplies all the muscles of the palate, via the pharyngeal plexus and the pharyngeal branch of the vagus nerve, except the tensor veli palatini which is supplied by the mandibular branch of the trigeminal nerve.

The Sternothyroid, Sternohyoid, and Omohyoid muscles are supplied by the ansa cervicalis while the thyrohyoid muscle is supplied by the hypoglossal nerve.

A decrease in the functional residual capacity (FRC) is the most important physiologic change to consider for such patients.

FRC is the sum of the expiratory reserve volume and the residual volume. It is the resting volume of the lung, and is an important marker for lung function. During this time, the alveolar pressure is equal to the atmospheric pressure. When morbidly obese individuals lie supine, the FRC decreases by as much as 40% because the abdominal contents push the diaphragm into the thoracic cavity.

Chest wall compliance is expected to reduce because of fat deposition surrounding adjacent structures.

Inspiratory reserve volume (IRV) is expected to increase, and peak expiratory flow is expected to decrease, however the decrease in FRC is more important to consider because of the risk of hypoxia secondary to premature airway closure and ventilation-perfusion mismatch.

The diaphragm divides the thoracic cavity from the abdominal cavity. Structures penetrate the diaphragm at different vertebral levels through openings in the diaphragm to communicate between the two cavities. The diaphragm has openings at three vertebral levels:

T8: vena cava, terminal branches of the right phrenic nerve
T10: oesophagus, vagal trunks, left anterior phrenic vessels, oesophageal branches of the left gastric vessels
T12: descending aorta, thoracic duct, azygous and hemi-azygous vein

Giardiasis is known to have a longer incubation time and doesn’t cause bloody diarrhoea.

Cholera usually doesn’t cause bloody diarrhoea.

Generally, most of the E.coli strains do not cause bloody diarrhoea.

Diverticulitis can be a cause of bloody stool but the history here points out to an infectious cause.

Campylobacter infection is the most probable cause as it is characterized by a prodrome, abdominal pain and bloody diarrhoea

pH is the negative log to the base 10 of hydrogen ion concentration:

So, what power produces the answer?

pH = – log10 [H+]

Making [H+] the subject:

[H+] = 10-pH

Substituting, [H+] = 10-7

One nanomole = 1 x 10-9 or 0.000000001

10-7 = 1x 0.0000001 or 10 x 0.00000001 or 100 x 0.000000001

100 nanomole

When using dry soda lime for VOCs, very high amounts of carbon monoxide may be produced, regardless of the inhalational anaesthetic agent used. The carbon monoxide produced is sufficient enough to cause cytotoxic and anaemic hypoxia. To prevent this, soda lime canisters are shaken well to even out the packing of granules. This can help to evenly distribute gas flow for proper CO2 absorption and ventilation.

Compound A is formed when dry soda lime, or soda lime in high temperature, reacts with the inhalational anaesthetic Sevoflurane. Animal studies have shown renal toxicity in rats, but renal adverse effects in humans are yet to be observed.

When monitors are not employed with VOCs, deleterious effects are not for certain. However, monitors not employed with vaporiser inside the circuit (VIC) can lead to significant adverse events.

The cricoid cartilage is a hyaline cartilage ring surrounding the trachea. It provides support for key phonation muscles.

The inferior border of the cricoid cartilage is attached to the thyroid cartilage and the inferior border is attached to the first tracheal ring through the cricotracheal ligament.

Application of pressure to the cricoid cartilage to reduce risk of aspiration of gastric contents (Sellick manoeuvre) does not stop tracheal aspiration and cannot stop regurgitation into the oesophagus.

A force of 44 newtons to the cricoid cartilage is needed to control regurgitation.

A forest plot is a graphical representation that summarizes the findings of several research, such as a meta-analysis of a series of randomized controlled trials.

The Kaplan-Meier estimate shows survival over time, for example, plotting the number of patients still alive seven years after chemotherapy for lung cancer.

Fisher’s exact test similarly uses contingency tables to assess statistical significance, however, it is typically used when sample sizes are small.

Chi-square test assesses whether an association exists between two categorical variables using the observed and expected frequencies. For instance, is social class (I-V) related to body mass index (BMI) category? Using the observed and anticipated frequencies, the Chi-square test determines whether a connection exists between two categorical variables. For example, is socio-economic status related to BMI category?

Linear regression is a technique which attempts to model the relationship between two variables by fitting a linear equation to observed data. Linear regression uses correlation between two continuous variables. As correlation only indicates the strength of an association only, it cannot be used to forecast the change in one variable when a second variable is altered.

This equation takes the form y = mx + c, where ‘y’ is the dependent variable, ‘x’ is the independent variable, ‘m’ is the slope of the line and ‘c’ is the intercept. In this example, for a range of heights, it would be possible to map a line of best fit to a scatter plot and thus predict the forced expiratory volume (FEV1) for an individual.

Closing capacity refers to volume of gas within the lungs at which the conducting small airways begin to close, that is, the point during expiration when small airways close.

It is calculated mathematically as:

Closing capacity = Closing volume (CV) + Residual volume (RV)

Functional residual capacity (FRC) is the volume of gas still present within the lungs post expiration.

Closing capacity is lower than the functional residual capacity in younger adults, but begins to rise to eventually equal, and then exceed it with increasing age (at about middle age), increasing intrabdominal pressure, decreasing blood flow in the pulmonary system and parenchymal disease within the pulmonary system.

Based on the presenting symptoms, this is the case of bacterial meningitis. The treatment of choice for bacterial meningitis is a cephalosporin. Cephalosporin acts by inhibiting bacterial cell wall synthesis.

Ketamine is primarily used for the induction and maintenance of anaesthesia. It induces dissociative anaesthesia. But it is contraindicated in cardiovascular diseases such as unstable angina or poorly controlled hypertension.

Tricyclic antidepressants (TCA) are primarily used as antidepressants which is important for the management of depression. These are second-line drugs next to SSRI. They work by competitively preventing re-uptake of amines (noradrenaline and serotonin) from the synaptic cleft so increasing their concentration. But TCA overdoses are toxic and have cardiovascular effects, central effects, and anticholinergics effects. Cardiovascular effects like prolonged QT and widened QRS at lower doses progressing to ventricular arrhythmias and refractory hypotension at higher doses can be life-threatening. When used in the perioperative period, it can lead to increased sensitivity to circulating catecholamines therefore care is needed perioperatively.

The structures in the porta hepatis from anterior to posterior are:

The ducts: Most anterior are the left and right hepatic ducts.

The arteries: Next are the left and right hepatic arteries

The veins: Next is the portal vein

The epiploic foramen of Winslow lies most posterior at the porta hepatis.

The diaphragm divides the thoracic cavity from the abdominal cavity. Structures penetrate the diaphragm at different vertebral levels through openings in the diaphragm to communicate between the two cavities. The diaphragm has openings at three vertebral levels:

T8: vena cava, terminal branches of the right phrenic nerve
T10: oesophagus, vagal trunks, left anterior phrenic vessels, oesophageal branches of the left gastric vessels
T12: descending aorta, thoracic duct, azygous and hemi-azygous vein

Detsky’s Modified cardiac risk classification system in patients undergoing non-cardiac surgery:

Age more than 70: 05 points

History of myocardial infarction:

Less than 6 months: 10 points
More than 6 months: 5 points

Angina Pectoris:

Angina with minimal exertion: 10 points

Angina at any level of exertion: 20 points

Pulmonary Oedema:

Within 7 days: 10 points
At any time: 5 points

Suspected aortic valve stenosis with valve area <0.6cm2: 20 points Arrhythmia: Any rhythm other than sinus or sinus with premature atrial complexes (PACs): 5 points More than 5 premature ventricular contractions: 5 points
Emergency Surgery: 10 points
Deficient general medical condition: 5 points

Risk classification:

Grade I: 0-15 points = low risk
Grade II: 15-30 points = moderate risk
Grade III: >30 points = high risk

This patient’s limited haematological profile includes mild normocytic anaemia and a normal platelet count.

Iron deficiency is the most common cause of anaemia during pregnancy. It affects 75 to 95 percent of patients. A haemoglobin level of less than 110 g/L in the first trimester and less than 105 g/L in the second and third trimesters is considered anaemia. There will usually be a low mean cell volume (MCV), mean cell haemoglobin (MCH), and mean cell haemoglobin concentration in addition to a low haemoglobin (MCHC). The MCV may be normal in mild cases of iron deficiency or coexisting vitamin B12 and folate deficiency.

To determine whether you have an iron deficiency, you’ll need to take more tests. Low serum ferritin (15 g/L) and less reliable indices like serum iron and total iron binding capacity are among them.

A number of factors contribute to iron deficiency in pregnancy, including:

Insufficient dietary iron to meet the mother’s and foetus’ nutritional needs
Multiple pregnancies
Blood loss, as well as
Absorption of iron from the gut is reduced.

The volume of plasma increases by about 50% during pregnancy, but the mass of red blood cells (RBCs) increases by only 30%. Dilutional anaemia is the result of this situation. From the first trimester to delivery, the RBC mass increases linearly, while the plasma volume plateaus, stabilises, or falls slightly near term. As a result, between 28 and 34 weeks of pregnancy, haemoglobin concentrations are at their lowest. The effects of haemodilution will be negated in this patient because she is 37 weeks pregnant.

Vitamin B12 and folate deficiency are less common causes of anaemia in pregnancy. The diagnosis could be ruled out if the MVC is normal.

During pregnancy, the platelet count drops, especially in the third trimester. Gestational thrombocytopenia is the medical term for this condition. It’s due to a combination of factors, including haemodilution and increased platelet activation and clearance. Pre-eclampsia and HELLP syndrome are common causes of thrombocytopenia. Pre-eclampsia isn’t the only cause of anaemia during pregnancy.

A typical blood picture of a haemoglobinopathy like sickle cell disease shows quantitative and qualitative defects, with the former leading to a severe anaemia exacerbated by haemodilution and other factors that contribute to iron deficiency. Microcytic cells are the most common type.

If the afterload and myocardiac contractility remains unchanged, an increase in the preload can be attributed to an increase in end-diastolic volume.

Preload can be defined as the initial stretching of the cardiac myocytes prior to contraction. Preload, therefore, is related to muscle sarcomere length. Because sarcomere length cannot be determined in the intact heart, other indices of preload are used such as ventricular end-diastolic volume or pressure. When venous return to the heart is increased, the end-diastolic pressure and volume of the ventricles are increased, which stretches the sarcomeres, thereby increasing their preload.

The renal arteries branch from the abdominal aorta just below the origin of the superior mesenteric artery. The right renal artery is higher and longer than the left renal artery. The left renal artery passes behind the left renal vein, the body of the pancreas, and the splenic vein.

The important landmarks of vessels arising from the abdominal aorta at different levels of vertebrae are:

T10 – oesophageal opening in the diaphragm

T12 – Coeliac trunk, aortic hiatus in the diaphragm

L1 – Left renal artery

L2 – Testicular or ovarian arteries

L3 – Inferior mesenteric artery

L4 – Bifurcation of the abdominal aorta

Heme a exists in cytochrome a and heme c in cytochrome c; they are both involved in the process of oxidative phosphorylation. 5′-Aminolevulinic acid synthase (ALA-S) is the regulated enzyme for heme synthesis in the liver and erythroid cells.

There are two forms of ALA Synthase, ALAS1, and ALAS2.

Myasthenic and cholinergic crises are two crises which are similar in their clinical presentation.

Myasthenic crisis can be caused by:
-lack of acetylcholine,
-poor compliance with medication,
-infection

Cholinergic crisis can be caused by excess cholinesterase inhibitor medication (mimicking organophosphate poisoning) causing excess acetylcholine.

Differentiation between the 2 crises is made by giving incremental doses of the short acting cholinesterase inhibitor, Edrophonium.
This increase acetylcholine levels and will make a myasthenic crisis better and a cholinergic crisis worse.

Primary FRCA is concerned with two issues. The first is a working knowledge of the Henderson-Hasselbalch equation, and the second is a working knowledge of logarithms and antilogarithms.

The pH at which the drug exists in 50 percent ionised and 50 percent unionised forms is known as the pKa.

To calculate the proportion of ionised to unionised form of a drug, use the Henderson-Hasselbalch equation.

pH = pKa + log ([A-]/[HA])

or

pH = pKa + log [(salt)/(acid)]
pH = pKa + log ([ionised]/[unionised])

Hence, if the pKa − pH = 0, then 50% of drug is ionised and 50% is unionised.

In this example:
7.4 = 8.4 + log ([ionised]/[unionised])
7.4 − 8.4 = log ([ionised]/[unionised])
log −1 = log ([ionised]/[unionised])

Simply put, the antilog is the inverse log calculation. In other words, if you know the logarithm of a number, you can use the antilog to find the value of the number. The antilogarithm’s definition is as follows:

y = antilog x = 10x

Antilog to the base 10 of 0 = 1, −1 = 0.1, −2 = 0.01, −3 = 0.001 and, −4 = 0.0001.

[A-]/[HA] = 0.1

Assuming that we can apply the approximation [A-] << [HA} then this means the acid is 0.1 x 100% = 10% ionised so the percentage of (non-ionized) acid will be 100% – 10% = 90%

At the ankle joint, midway between the malleoli, the anterior tibial artery changes names, becoming the dorsalis pedis artery (dorsal artery of the foot).

The dorsalis pedis artery is palpated against the underlying tarsals, immediately lateral to the tendon of extensor hallucis longus, from the midpoint between the malleoli to the proximal end of the first intermetatarsal space.

The popliteal artery forms the anterior tibial artery.
The tibioperoneal trunk is a branch of the popliteal artery.
The peroneal artery (also known as the fibular artery) supplies the lateral compartment of the leg.
The external iliac artery is formed from the common iliac artery at the level of the pelvis.

Trigeminal neuralgia is characterized by excruciating paroxysms of pain in the lips, gums, cheek, or chin and, very rarely, in the distribution of the fifth nerve. The pain seldom lasts more than a few seconds or a minute or two but may be so intense that the patient winces, hence the term tic. The paroxysms, experienced as single jabs or clusters, tend to recur frequently, both day and night, for several weeks at a time. They may occur spontaneously or with movements of affected areas evoked by speaking, chewing, or smiling. Another characteristic feature is the presence of trigger zones, typically on the face, lips, or tongue, that provoke attacks; patients may report that tactile stimuli – e.g., washing the face, brushing the teeth, or exposure to a draft of air – generate excruciating pain. An essential feature of trigeminal neuralgia is that objective signs of sensory loss cannot be demonstrated on examination.

Trigeminal neuralgia is relatively common, with an estimated annual incidence of 4–8 per 100,000 individuals. Middle-aged and elderly persons are affected primarily, and ,60% of cases occur in women. Onset is typically sudden, and bouts tend to persist for weeks or months before remitting spontaneously. Remissions may be long-lasting, but in most patients, the disorder ultimately recurs.

An ESR or CRP is indicated if temporal arteritis is suspected. In typical cases of trigeminal neuralgia, neuroimaging studies are usually unnecessary but may be valuable if MS is a consideration or in assessing overlying vascular lesions in order to plan for decompression surgery.

Parotidectomy is basically an anatomical dissection. Identification of the facial nerve trunk is essential during parotid gland surgery because facial nerve injury is the most daunting potential complication of parotid gland surgery owing to the close relation between the gland and the extratemporal course of the facial nerve. After exiting the stylomastoid foramen, the facial nerve enters the substance of the parotid gland and then gives off five terminal branches:
From superior to inferior, these are the:
– Temporal branch supplying the extrinsic ear muscles, occipitofrontalis and orbicularis oculi
– Zygomatic branch supplying orbicularis oculi
– Buccal branch supplying buccinator and the lip muscles
– Mandibular branch supplying the muscles of the lower lip and chin
– Cervical branch supplying platysma.

There are two approaches to identify the facial nerve trunk during parotidectomy—conventional antegrade dissection of the facial nerve, and retrograde dissection. Numerous soft tissue and bony landmarks have been proposed to assist the surgeon in the early identification of this nerve. Most commonly used anatomical landmarks to identify facial nerve trunk are stylomastoid foramen, tympanomastoid suture (TMS), posterior belly of digastric (PBD), tragal pointer (TP), mastoid process and peripheral branches of the facial nerve.

A major source of caloric expenditure and oxygen consumption in the body is work of breathing (WOB) and 70% of this is to overcome elastic forces. The remaining 30% is for flow-resistive work

In a normal patient breathing normally, the total area of hysteresis pressure volume curve represents the flow-resistive WOB.

The area of the expiratory resistive work increases during an asthma attack making the compliance curve larger in area. The larger the area the greater the work required to breathe.

Smoking is a major risk factor associated with perioperative respiratory and cardiovascular complications. Evidence also suggests that cigarette smoking causes imbalance in the prostaglandins and promotes vasoconstriction and excessive platelet aggregation. Two of the constituents of cigarette smoke, nicotine and carbon monoxide, have adverse cardiovascular effects. Carbon monoxide increases the incidence of arrhythmias and has a negative ionotropic effect both in animals and humans.

Smoking causes an increase in carboxyhaemoglobin levels, resulting in a leftward shift in which appears to represent a risk factor for some of these cardiovascular complications.

There are two mechanisms responsible for the leftward shift of oxyhaemoglobin dissociation curve when carbon monoxide is present in the blood. Carbon monoxide has a direct effect on oxyhaemoglobin, causing a leftward shift of the oxygen dissociation curve, and carbon monoxide also reduces the formation of 2,3-DPG by inhibiting glycolysis in the erythrocyte. Nicotine, on the other hand, has a stimulatory effect on the autonomic nervous system. The effects of nicotine on the cardiovascular system last less than 30 min.

The superior thyroid artery is the first branch of the external carotid artery. The other branches of the external carotid artery are:
1. Superior thyroid artery
2. Ascending pharyngeal artery
3. Lingual artery
4. Facial artery
5. Occipital artery
6. Posterior auricular artery
7. Maxillary artery
8. Superficial temporal artery

The inferior thyroid artery is derived from the thyrocervical trunk.

Since an arterial pressure transducer, and every other measuring apparatus, is prone to errors due to offset and gradient drifts, regular calibration is required to maintain accuracy of the instrument. The two-point calibration pressure values of 0 mmHg and 200 mmHg are within the physiologic range and can best compensate for the gradient drift.

In general practice, majority of phase 3 trials and some of the trials conducted in phase 2 are randomized. Because phase 4 trials require a huge sample size, they are not randomized as much. The primal reason behind conducting phase 3 trials is to test the efficiency and safety in a significant sample population. At this point it is assumed that the drug is effective up to a certain extent.

During a case-control study, subjects that exhibit outcomes of interest are compared with those who don’t show the expected outcome. The extent of exposure to a particular risk factor is then matched between cases and controls. If the exposure among cases surpasses controls, it becomes a risk factor for the outcome that is being studied.

Pilot studies are conducted on a lower and much smaller level, to assess if a randomized controlled trial of the crucial components of a study will be plausible.

Phase 4 trials are the ones that are conducted after its established that the drug is effective and is approved by the regulating authority for use. These trials are concerned with the side effects and potential risks associated with the long term usage of the drug.

When a person forcefully expires against a closed glottis, changes occur in intrathoracic pressure that dramatically affect venous return, cardiac output, arterial pressure, and heart rate. This forced expiratory effort is called a Valsalva maneuver.

Initially during a Valsalva, intrathoracic (intrapleural) pressure becomes very positive due to compression of the thoracic organs by the contracting rib cage. This increased external pressure on the heart and thoracic blood vessels compresses the vessels and cardiac chambers by decreasing the transmural pressure across their walls. Venous compression, and the accompanying large increase in right atrial pressure, impedes venous return into the thorax. This reduced venous return, and along with compression of the cardiac chambers, reduces cardiac filling and preload despite a large increase in intrachamber pressures. Reduced filling and preload leads to a fall in cardiac output by the Frank-Starling mechanism. At the same time, compression of the thoracic aorta transiently increases aortic pressure (phase I); however, aortic pressure begins to fall (phase II) after a few seconds because cardiac output falls. Changes in heart rate are reciprocal to the changes in aortic pressure due to the operation of the baroreceptor reflex. During phase I, heart rate decreases because aortic pressure is elevated; during phase II, heart rate increases as the aortic pressure falls.

When the person starts to breathe normally again, the intrathoracic pressure declines to normal levels, the aortic pressure briefly decreases as the external compression on the aorta is removed, and heart rate briefly increases reflexively (phase III). This is followed by an increase in aortic pressure (and reflex decrease in heart rate) as the cardiac output suddenly increases in response to a rapid increase in cardiac filling (phase IV). Aortic pressure also rises above normal because of a baroreceptor, sympathetic-mediated increase in systemic vascular resistance that occurred during the Valsava.

Static lung compliance refers to the change in volume within the lung per given change in unit pressure. It is usually measured when air flow is absent, such as during pauses in inhalation and exhalation.

It is a combination of:

Chest wall compliance: normal value is 200 mL/cmH2O
Lung tissue compliance: normal value is 200 mL/ cmH2O

It is represented mathematically as:

1/Crs = 1/Cl + 1/Ccw

Where,

Crs = total compliance of the respiratory system
Cl = compliance of the lung
Ccw = compliance of the chest wall

Therefore in this case:

1/Crs = 1/200 + 1/200

1/Crs = 0.005 + 0.005 = 0.01

1/Ct = 0.01

Rearranging equation gives:

Ct = 1/0.01 = 100 mL/cmH2O.

The costal elements of the seventh cervical vertebrae form projections known as cervical ribs, which are present in approximately 0.5% – 1 % individuals.

A cervical rib commonly comprises of a head, neck and tubercle. The body of the rib varies from person to person. It extends into the posterior triangle of the neck, where it is either free anteriorly, or attached to the first rib / sternum.

Patients with a cervical rib mostly are asymptomatic and it is usually diagnosed as an incidental finding on chest x-ray. However, in some cases, the subclavian artery and the lower trunk of the brachial plexus are compressed where they pass over the cervical rib. This leads to a condition known as ”neurovascular compression syndrome,” in which these neurovascular structures are compressed between the cervical rib and scalenus anterior.

The most common cause of neurogenic symptoms in approximately 80% of the patients with cervical rib is neck trauma.

In most cases, the tingling, numbness and impaired circulation to the upper limb appears only after puberty. This is because the neck elongates, and the shoulders droop slightly.

Propofol is cleared at the fastest rate at the rate of 60ml/kg/min.

Clearance rate of other drugs are as follows:
– Thiopental: 3.5 ml/kg/min
– Methohexitone: 11 ml/kg/min
– Ketamine: 17 ml/kg/min
– Etomidate: 10-20 ml/kg/min

After a paediatric case, you’ll frequently have to calculate and prescribe maintenance fluids. The ‘4-2-1 rule’ should be used as a guideline:

1st 10 kg – 4 ml/kg/hr
2nd 10 kg – 2 ml/kg/hr
Subsequent kg – 1 ml/kg/hr

Hence

1st 10 kg = 4 × 10 = 40 ml
2nd 10 kg = 2 × 10 = 20 ml
Subsequent kg = 1 × 1 = 1 ml
Total = 61 ml/hr

61 × 12 = 732 ml over 12 hrs.

This scenario describes rebreathing management.

Changes is exhaustion of the soda lime and a progressive rise in circuit deadspace is the most likely explanation for the capnograph.

It is important that the soda lime canister is inspected for a change in colour of the granules. Initially fresh gas flow should be increased and then if necessary, replace the soda lime granules. Other strategies include changing to another circuit or bypassing the soda lime canister after the fresh gas flow is increased.

Any other causes of increased equipment deadspace should be excluded.

Intraoperative hypercarbia can be caused by:

1. Hypoventilation – Breathing spontaneously; drugs which include anaesthetic agents, opioids, residual neuromuscular blockade, pre-existing respiratory or neuromuscular disease and cerebrovascular accident.
2. Controlled ventilation- circuit leaks, disconnection, miscalculation of patient’s minute volume.
3. Rebreathing – Soda lime exhaustion with circle, inadequate fresh gas flow into Mapleson circuits, increased breathing system deadspace.
4. Endogenous source – Tourniquet release, hypermetabolic states (MH or thyroid storm) and release of vascular clamps.
5. Exogenous source – Absorption of CO2 absorption from the pneumoperitoneum.

Pulse oximeters combine the principles of oximetry and plethysmography to noninvasively measure oxygen saturation in arterial blood. A sensor containing two or three light emitting diodes and a photodiode is placed across a perfused body part, commonly a finger, to be transilluminated. Oximetry depends on oxyhaemoglobin and deoxyhaemoglobin, and their ability to absorb the beams of light produced by the light emitting diodes: red light at 660 nm and infrared light at 960 nm.

The isosbestic point is the point wherein two different substances absorb light to the same extent. For oxyhaemoglobin and deoxyhaemoglobin, the points are at 590 nm and 805 nm. These are considered reference points where light absorption is independent of the degree of saturation.

Non-constant absorption of light is often due to the presence of an arterial pulsation, whilst constant absorption of light is seen in non-pulsatile tissues.

Most pulse oximeters are inaccurate at low SpO2, but is accurate at +/- 2% within the range of 70% to 100% SpO2. All pulse oximeters demonstrate a delay in between changes in SaO2 and SpO2, and display average readings every 10 to 20 seconds, hence they are unable to detect acute desaturation episodes.

Direct laryngoscopy are performed using laryngoscopes and they can be classed according to the shape of the blade as curved or straight.

Miller, Soper, Wisconsin and Seward are examples of straight blade laryngoscopes. Straight blades are commonly used for intubating neonates and infants but can be used in adults too.

The tip of the miller blade is advanced over the epiglottis to the tracheal entrance then lifted in order to view the vocal cords.

The RIGHT-SIDED Macintosh blade is used in adults while the left-sided blade may be used in conditions that make intubation with standard blade difficult e.g. facial deformities.

The McCoy laryngoscope is based on the STANDARD MACINTOSH blade not Robertshaw’s. It has a lever operated hinged tip, which improves the view during laryngoscopy.

Polio blade is mounted at an angle of 120-135 degrees to the handle. Originally designed for use during the polio epidemic ​in intubation patients within iron lung ventilators, it is now useful in patients with conditions like breast hypertrophy, barrel chest, and restricted neck mobility.

Ligamentum venosum is an anterior relation of the liver: The ligamentum venosum, the fibrous remnant of the ductus venosus of the fetal circulation, lies posterior to the liver. It lies in the fossa for ductus venosus that separates the caudate lobe and the left lobe of the liver.

The portal triad contains three important tubes: 1. Proper hepatic artery 2. Hepatic portal vein 3. Bile ductules It also contains lymphatic vessels and a branch of the vagus nerve.

The bare area of the liver is a large triangular area that is devoid of any peritoneal covering. The bare area is attached directly to the diaphragm by loose connective tissue. This nonperitoneal area is created by a wide separation between the coronary ligaments.

The porta hepatis is a fissure in the inferior surface of the liver. All the neurovascular structures (except the hepatic veins) and hepatic ducts enter or leave the liver via the porta hepatis. It contains the sympathetic branch to the liver and gallbladder and the parasympathetic, hepatic branch of the vagus nerve. The caudate lobe (segment I) lies in the lesser sac on the inferior surface of the liver between the IVC on the right, the ligamentum venosum on the left, and the porta hepatis in front

There are different effects of electrocution and these can be shown in the table below.

Current Effect
1 mA Tingling
5 mA Pain
15 mA Tonic muscle contraction
50 mA Respiratory arrest
100 mA Ventricular fibrillation and cardiac arrest

The static-response defines how a measuring system behaves while it is in equilibrium (i.e. when the measured values are not changing). If the value being measured changes over time, the reaction of a measuring system will change as well which would be a dynamic response.
The dynamic response of a measuring system can be subdivided into zero-order, first-order and second-order responses:

Zero-order:
Consider a thermometer that has been left in a room for a week. The thermometer will display the current ambient temperature when you enter the room.

First-order:
Consider the use of a mercury thermometer to check a patient’s temperature. It is comprised of a mercury column that expands as it warms up. The scale’s initial temperature is room temperature, but when it’s placed under the patient’s tongue, the temperature readings rise until they reach body temperature.

Second-order
Consider putting weights on a mechanical weighing scale. The weight as reported on the measuring dial, will wobble around the correct value at first until reaching equilibrium. An example of this is in clinical practice is the direct measurement of arterial pressure with a transducer. The value of the input fluctuates around a central point.

Drift is the progressive deterioration of a measurement system’s precision. With time, the measurement deviates from the genuine, calibrated value. The graph between this measurement and the real value should, ideally, be linear (e.g. on the y-axis the measured end-tidal CO2 against true value of the end-tidal CO2). Drift is split into three types: zero-offset, gradient, and zonal drift.

The renal effects of atrial natriuretic peptide (ANP) secretion are as follows:

Increased glomerular filtration rate by dilating the afferent glomerular arteriole. Moreover, it constricts the efferent glomerular arteriole, and relaxes the mesangial cells.
Reduces sodium reabsorption in the collecting ducts and distal convoluted tubule.
The renin-angiotensin system (RAS) is inhibited.
Blood flow in the vasa recta is increased.

Because plasma osmolality is unlikely to change, hypothalamic osmoreceptors are unaffected.

The plasma protein has a molecular weight of 66 kDa, is not normally filtered into the proximal convoluted tubule, and has no osmotic diuretic effect.

The following are some basic assumptions:

Extracellular fluid (ECF) makes up one-third of total body water (TBW), while intracellular fluid makes up the other two-thirds (ICF)
One-quarter plasma and three-quarters interstitial fluid make up ECF (ISF)
The volume receptors in the atria have a 7-10% blood volume change threshold.
The osmoreceptors are sensitive to changes in osmolality of 1-2 percent.
The normal plasma osmolality before the transfusion is 287-290 mOsm/kg.
The plasma protein solution is a colloid that is only delivered to the intravascular compartment. The tonicity remains unchanged.
The blood volume increases by 20%, from 5,000 mls to 6,000 mls. This is higher than the volume receptor threshold of 7 to 10%.

In statistical terms, correlation is used to denote association between two quantitative variables.

The degree of association is measured by a correlation coefficient, denoted by r. The correlation coefficient is measured on a scale that varies from + 1 through 0 to – 1. Complete correlation between two variables is expressed by either + 1 or -1. When one variable increases as the other increases the correlation is positive; when one decreases as the other increases it is negative. Complete absence of correlation is represented by 0.

The two methods are not synonymous as correlation measures the degree of relationship between two variables whereas regression analysis is about how one variable affects another or what changes it has on the other variable. Both are also shown by a different graphical representation.

The aminosteroid rocuronium is the neuromuscular blocking agent in question.

0.3 mg/kg is the effective dose 95 (ED95) (the dose required to depress the twitch height by 95 percent )
The dose for intubation is 0.6 mg/kg.
75 seconds is the time it takes to reach 95 percent depression of the first twitch of the train of four (ToF) or the onset time.
The clinical duration or time to 25% recovery of the first twitch of the train of four (ToF) is 33 minutes.

A modified cyclodextrin can quickly reverse both rocuronium and vecuronium (sugammadex).

It is more fat-soluble than vecuronium, with the liver absorbing the majority of the drug and excreting it in the bile. The only metabolite found in the blood (17-desacetylrocuronium) is 20 times less potent than the parent drug and is unlikely to cause neuromuscular block.

Despite its quick onset of action (60-90 seconds), suxamethonium arguably is still the neuromuscular blocker of choice for a quick sequence induction. Rocuronium is becoming increasingly popular for this purpose.

The concentration of solute particles per litre (mosm/L) = the osmolarity of a solution. Changes in water content, ambient temperature, and pressure affects osmolarity. The osmolarity of any solution can be calculated by adding the concentration of key solutes in it.

Individual manufacturers of crystalloids and colloids may have different absolute values but they are similar to these.

0.45% N. Saline with 5% glucose:
Tonicity – hypertonic
Osmolarity – 405 mosm/L
Kilocalories (kCal) – 107

0.9% N. Saline:
Tonicity – isotonic
Osmolarity – 308 mosm/L
Kilocalories (kCal) – 0

5% Dextrose:
Tonicity – isotonic
Osmolarity – 253 mosm/L
Kilocalories (kCal) – 170

Gelofusine (154 mmol/L Na, 120 mmol/L Cl):
Tonicity – isotonic
Osmolarity – 274 mosm/L
Kilocalories (kCal) – 0

Hartmann’s solution:
Tonicity – isotonic
Osmolarity – 273 mosm/L
Kilocalories (kCal) – 9

Sodium concentration for different fluids
3% N saline 513 mmol/L
5% N saline 856 mmol/L
0.9% N saline 154 mmol/L
Hartmann’s solution 131 mmol/L
0.45% N saline with 5% glucose 77 mmol/L

This means that:

500 mL 5% N saline contains 428 mmol of sodium
1000 mL 3% N saline contains 513 mmol of sodium
3500 mL 0.9% N saline contains 539 mmol of sodium
4000 mL Hartmann’s contains 524 mmol of sodium
6000 mL 0.45% N saline with 5% glucose contains 462 mmol of sodium.

Propofol infusion syndrome (PRIS) is characterized by lactic acidosis, bradyarrhythmia, rhabdomyolysis, cardiac and renal failure, and often leads to death. So, lactate monitoring is advised in patients with propofol infusion syndrome.

Standard error can be calculated by the following formula:

Standard Error= (Standard Deviation)/√(Sample Size)
= (12) / √(64)
= 12 / 8
= 1.5

Adrenaline acts on ?1, ?2,?1, and ?2 receptors and also on dopamine receptors (D1, D2) and have sympathomimetic effects.

Natural catecholamines are Adrenaline, Noradrenaline, and Dopamine

Adrenaline is a sympathomimetic amine with both alpha and beta-adrenergic stimulating properties.
Adrenaline is the drug of choice for anaphylactic shock
Adrenaline is also used in patients with cardiac arrest. The preferred route is i.v. followed by the intra-osseous and endotracheal route.

Adrenaline is released by the adrenal glands, acts on ? 1 and 2, ? 1 and 2 receptors, and is responsible for fight or flight response.

It acts on ? 2 receptors in skeletal muscle vessels-causing vasodilation.

It acts on ? adrenergic receptors to inhibit insulin secretion by the pancreas. It also stimulates glycogenolysis in the liver and muscle, stimulates glycolysis in muscle.

It acts on ? adrenergic receptors to stimulate glucagon secretion in the pancreas
It also stimulates Adrenocorticotrophic Hormone (ACTH) and stimulates lipolysis by adipose tissue

The cardiac muscle’s contractile fibres have a much more stable resting potential than its conductive fibres. In the ventricular fibres it is -90mV and in the atrial fibres it is -80mV.

The cardiac action potential has several phases which have different mechanisms of action as seen below:

Phase 0: Rapid depolarisation – caused by a rapid sodium influx.
These channels automatically deactivate after a few ms. (QRS complex)

Phase 1: caused by early repolarisation and an efflux of potassium.

Phase 2: Plateau – caused by a slow influx of calcium.

Phase 3 – Final repolarisation – caused by an efflux of potassium.

Phase 4 – Restoration of ionic concentrations – The resting potential is restored by Na+/K+ATPase.
There is slow entry of Na+into the cell which decreases the potential difference until the threshold potential is reached. This then triggers a new action potential

Of note, cardiac muscle remains contracted 10-15 times longer than skeletal muscle.

Different sites have different conduction velocities:
1. Atrial conduction – Spreads along ordinary atrial myocardial fibres at 1 m/sec

2. AV node conduction – 0.05 m/sec

3. Ventricular conduction – Purkinje fibres are of large diameter and achieve velocities of 2-4 m/sec, the fastest conduction in the heart. This allows a rapid and coordinated contraction of the ventricles

The area described in the question is supplied by the intercostobrachial nerve, which provides sensory innervation to the portions of the axilla, tail of the breast, lateral chest wall and medial side of the arm.

It is a common for it to be ‘missed’ during administration of local anaesthesia because of its very superficial anatomic course. It may be anesthetized by giving an analgesia from the upper border of the biceps at the anterior axillary fold, to the margin of the triceps by the axillary floor.

The clinical picture best describes a probable drug interaction with pethidine.

Phenelzine, a monoamine oxidase (MAO) inhibitor, when given with pethidine, an opioid analgesic, may lead to episodes of hypertension, rigidity, excitation, hyperpyrexia, seizures, coma and death. Studies have shown that pethidine reacts more significantly with MAO inhibitors than morphine.

When pethidine is metabolised to normeperidine, it acts as a serotonin reuptake inhibitor and cause an increase in serotonin levels in the brain. MAO inhibitors can also lead to elevated levels of serotonin because of its mechanism of action by inhibiting the enzyme monoamine oxidase that degrades serotonin.

The excess serotonin levels may lead to serotonin syndrome, of which some of the common precipitating drugs are selective serotonin reuptake inhibitors, MAO inhibitors, tricyclic antidepressants, meperidine, and St. John’s Wort. Onset of symptoms is within hours, which includes fever, agitation, tremor, clonus, hyperreflexia and diaphoresis.

Drug interaction between phenelzine and paracetamol do not commonly precipitate serotonin syndrome.

Neuroleptic malignant syndrome is due to dopamine antagonism, precipitated commonly by antipsychotics. Its onset of symptoms occur in 1 to 3 days, and is characterized by fever, encephalopathy, unstable vitals signs, elevated CPK, and rigidity.

Altered mental status is the most common manifestation of sepsis-associated encephalopathy. Patient also exhibit confusional states and inappropriate behaviour. In some cases, this may lead to coma and death.

For establishing a cause effect relationship, following criteria must be met:

1. Coherence & Consistency

2. Temporal Precedence

3. Specificity

As can be seen, sensitivity (The probability of a positive test) is not among these deciding factors..

Propofol is a short-acting medication used for starting and maintenance of general anaesthesia, sedation for mechanically ventilated adults, and procedural sedation.
The dose of propofol is 1-2 mg/kg.

Dose of some other important drugs are listed below:
Thiopental dose: 3-7 mg/kg
Ketamine dose: 1-2 mg/kg
Etomidate dose: 0.3 mg/kg
Methohexitone dose: 1.0-1.5 mg/kg

Ketamine is a phencyclidine (hallucinogenic) derivative that is administered in a dose of 2 mg/kg and acts by blocking NMDA (N-methyl-D-aspartate) receptors of glutamate.

It is a powerful bronchodilator agent and is, therefore, an intravenous anaesthetic of choice in bronchial asthma (halothane is an inhalational anaesthetic agent of choice for bronchial asthma). It is also used in the management of refractory status epilepticus.

It is an acid solution with an elimination half-life of three hours.

It has S (+) enantiomer and R (-) enantiomer. the S(+) enantiomer is two to four times more potent than the R(-) and is less likely to produce hallucinations.

Its use is contraindicated in patients with ischaemic heart disease because it increased sympathetic outflow leading to tachycardia and increased cardiac output which in turn increases the myocardial oxygen demand.

Amiodarone is the longest-acting anti-arrhythmic drug. It possesses the action of all classes of antiarrhythmic drugs (Sodium channel blockade, Beta blockade, Potassium channel blockade, and Calcium channel blockade). Due to this property, it has the widest anti-arrhythmic spectrum and thus can be used in both broad and narrow complex tachyarrhythmia.

Adenosine is shortest acting anti-arrhythmic drug.

Lesser the potency of the drug, the higher the dose required to produce maximal receptor occupation. So, the least potent drug will have a log dose-response curve furthest to the right on X-axis.

Based on the option given, tramadol is the least potent drug and thus higher dose is required to produce maximal opioid receptor occupation.

Thus, Tramadol is the least potent opioid with a log dose-response curve furthest to the right on X-axis.

Note, Fentanyl is the most potent opioid with a log dose-response curve furthest to the left on the X-axis.

Ventricular fibrillation (VT) is an arrhythmia caused by a distortion in the organized contraction of the ventricles leading to an inability to pump blood out into the body.

Amiodarone is an anti arrhythmic drug used for the treatment of ventricular and atrial fibrillations. It is the gold standard of treatment for refractory pulseless ventricular tachycardia (VT) and ventricular fibrillation (VF).

Guidelines for emergency treatment state that only the rescuer carrying out chest compressions on the patient may stand near the defibrillator as it charges.

Cardio-pulmonary resuscitation (CPR) during cardiac arrest is required for 2 minute cycles.

Hypovolaemia is as a cause of pulseless electrical activity (PEA) can be reversed using fluid resuscitation, whereas hypotension during cardiac arrest is either persistent or undetectable and is therefore irreversible.

Hyperkalaemia and hypocalcaemia are treated using calcium salts, but calcium chloride is often preferred over calcium gluconate.

During a pulseless VT or VF, a single precordial thump will be effective if administered within the first seconds of the occurrence of a shockable rhythm.

The left coronary artery arises from the left posterior aortic sinus and divides into the circumflex arteries and the left anterior descending (LAD) artery.

The right coronary artery arises from the anterior aortic sinus and supplies:
– the right ventricle
– part of the interventricular septum
– the atrioventricular (A-V) node and
– in 85% of cases the inferior part of the left ventricle.
The right coronary artery provides a posterior interventricular branch and a marginal branch that anastomoses with the LAD at the apex.

The oblique vein together with the small, middle and great cardiac veins drain into the coronary sinus, which drains into the right atrium.

The anterior cardiac vein drains directly into the right atrium.

Noradrenaline has a short half-life of about 2 minutes. It is rapidly cleared from plasma by a combination of cellular reuptake and metabolism.

It acts as sympathomimetics by acting on ?1 receptors and also on ? receptors.

It decreases renal and hepatic blood flow.

Norepinephrine is metabolized by the enzymes monoamine oxidase and catechol-O-methyltransferase to 3-methoxy-4-hydroxymandelic acid and 3-methoxy-4-hydroxyphenylglycol (MHPG).

Natural catecholamines are Adrenaline, Noradrenaline, and Dopamine

Dopamine (DA) is a dopaminergic (D1 and D2) as well as adrenergic ? and?1 (but not ?2 ) agonist.

The D1 receptors in renal and mesenteric blood vessels are the most sensitive: i.v. infusion of a low dose of DA dilates these vessels (by raising intracellular cAMP). This increases g.f.r. In addition, DA exerts a natriuretic effect by D1 receptors on proximal tubular cells.

Moderately high doses produce a positive inotropic (direct?1 and D1 action + that due to NA release), but the little chronotropic effect on the heart.

Vasoconstriction (?1 action) occurs only when large doses are infused.

At doses normally employed, it raises cardiac output and systolic BP with little effect on diastolic BP. It has practically no effect on nonvascular ? and ? receptors; does not penetrate the blood-brain barrier—no CNS effects.

Dopamine is used in patients with cardiogenic or septic shock and severe CHF wherein it increases BP and urine outflow.

It is administered by i.v. infusion (0.2–1 mg/min) which is regulated by monitoring BP and rate of urine formation

During analytical stage a technique called stratification is used for controlling confounding variables. This technique involves sorting out the data into discernible groups.

Normal distribution, also called Gaussian distribution, the most common distribution function for independent, randomly generated variables, and describes the spread for many biological and clinical measurements.

Properties of the Normal distribution

symmetrical i.e. Mean = mode = median

68.3% of values lie within 1 SD of the mean

95.4% of values lie within 2 SD of the mean

99.7% of values lie within 3 SD of the mean

The empirical rule, or the 68-95-99.7 rule, tells you where most of the values lie in a normal distribution: Around 68% of values are within 1 standard deviation of the mean.

Around 95% of values are within 2 standard deviations of the mean. Around 99.7% of values are within 3 standard deviations of the mean.
the standard deviation (SD) is a measure of how much dispersion exists from the mean.

SD = square root (variance)

The empirical rule, or the 68-95-99.7 rule states where most of the values lie in a normal distribution. Around 68% of values fall within 1 S.D of the mean, about 95% within 2 S.D of the mean, and about 99.7% of values within 3 S.D of the mean. Therefore, 95.4% is the most reasonable answer if results are normally distributed.

A patient presenting with symptomatic asthma should be assessed for severity to determine appropriate management options. Indications of acute severe asthma are:

Peak expiratory flow rate (PEFR): 33-50% best/predicted
Respiratory rate: ≥25/min
Heart rate: ≥110/min
Inability to finish a complete sentence in a single breath.

Oxygen saturation should be measured. Any measurement of an oxygen saturation of 92% or less, either on air or on oxygen, indicates severe, life threatening asthma, and requires an arterial blood gas (ABG) to detect normo- or hypercarbia.

A chest x-ray would not be routine as it will not provide any relevant information. It is only required in specific cases, including:
Diagnosis of a subcutaneous emphysema
Indications of a unilateral pneumothorax
Indications of a lobar collapse of consolidation
Treatment-resistance life-threatening asthma
If mechanical ventilation is indicated

A peak expiratory flow rate (PEFR) can provide relevant information to help distinguish between acute, moderate, severe and life threatening asthma. However, it is not necessary as other parameters exist that can also help make the same distinction.

An ECG is indicated in this case as the patient has tachycardia and tachypnoea which are indicative of acute severe asthma. The ECG would indicate if arrhythmia is also present which would suggest life-threatening asthma.

Elimination of phenytoin from the body follows first-order kinetics. This means that the rate of elimination is proportional to plasma concentration.

The rate of elimination can be described by the equation:

C = C0·e-kt

Where:

C = drug concentration
C0 = drug concentration at time zero (extrapolated)
k = Rate constant
t = Time

Enzyme systems become saturated when phenytoin concentrations exceed the normal range and elimination of the drug becomes zero-order. At this point, the drug is metabolised at a fixed rate and metabolism is independent of plasma concentration.

Aspirin and ethyl alcohol are other drugs that behave this way.

The SI unit of pressure is the pascal (Pa) and it is equal to one newton (N) per square meter (m2) or N/m2.

1 atmosphere (atm) is the equivalent of:

101325 Pa760 mmHg
1.01325 bar
1033.23 cmH2O.
14.69 pounds per square inch (psi)
1013.25 millibar (mbar) or hectopascals (hPa), and

14.69 psi is equal to one atmosphere. The other values are equal to two atmospheres of pressure.

The Purkinje system, as well as the action potentials of ventricular and atrial myocytes, have the same ionic changes. It lasts about 200 milliseconds and has a resting membrane potential, as well as fast depolarisation and plateau phases.

There are five stages to the process:

Increased Na+ and decreased K+ conductance in Phase 0 (rapid depolarisation).
1st phase (initial repolarisation) : Na+ conductance decreased, while K+ conductance increased.
Phase two (plateau phase) : Ca2+ conductance increased
Phase three (repolarisation phase) : Lower Ca2+ conductance and higher K+ conductance
4th Phase (resting membrane potential) : K+ conductance increased, Na+ conductance decreased, and Ca2+ conductance decreased.

Serum specific IgE assays against allergen sources/molecules are the most commonly used in vitro diagnostic approach. The measurement of specific IgE recognizing allergenic epitopes can be achieved both through the usage of single reagents (singleplex) or with a pre-defined panel of a number of molecules to be tested simultaneously (multiplex).

Several clinical entities have been described and those occurring immediately after drug exposure are immunoglobulin E (IgE)-mediated and explored by skin testing and by the in vitro measurement of serum-specific IgE. The sensitivity of these tests is not 100% and even for patients with a clear positive history, a drug provocation test may be required in order to confirm the diagnosis. The advantages of the in vitro determination of specific IgE antibodies when compared with in vivo testing are that the former poses no direct risk to the patient and does not require personnel with expertise. Even though in vitro tests are recommended in immediate hypersensitivity reactions, their exact place in the diagnostic procedure is not clear and certain authors do not use this method in daily practice. In one study, in terms of sensitivity, 11 of 26 patients (42%) with negative skin tests and a positive drug provocation challenge (or repeated clinical history) had specific IgE to benzylpenicilloyl or amoxicilloyl (4). The specificity of the test was 95–100%. Therefore, IgE measurements can avoid a potentially harmful drug provocation test.

An elevated serum tryptase does not differentiate between type 1 and type 2 hypersensitivity reaction. It indicates mast cell degranulation.

RAST is a useful aid to improve the overall diagnosis of drug allergies by using radioactive detection. This, however, is now rarely used.

Quantification of basophil activation by CD63 expression can be done by flow cytometry, which forms the basis of experimental drug-induced basophil stimulation tests.

The most common cause of hypoparathyroidism is injury or removing the parathyroid glands. They can be injured accidentally during surgery to remove the thyroid as they are located posterior to the thyroid gland.

A result of both low parathyroid hormone and low calcium is likely to mean that the parathyroid glands are not responding to hypocalcaemia. The hypocalcaemia can cause confusion, and the stay in the hospital is likely to refer to her surgery.

While a parathyroid adenoma is fairly common and can cause hypoparathyroidism, it much more likely causes hyperparathyroidism.

Chronic kidney disease is likely to cause hypocalcaemia, which would increase parathyroid hormone production in an attempt to increase calcium levels, causing hyperparathyroidism. Vitamin D is activated by the kidneys and then binds to calcium to be absorbed in the terminal ileum so that a deficiency would cause hyperparathyroidism.

The membranous urethra is the shortest part of the urethra and the least dilatable part of it.

This is as a result of it being surrounded by the external urethral sphincter which is made up of striated muscle and controls voluntary urine flow from the bladder to the urethra.

The axillary nerve lies behind the axillary artery initially, and in front of the subscapularis. It passes downward to the lower border of the subscapularis muscle.

In company with the posterior humeral circumflex artery and vein, it winds backward through a quadrilateral space bounded above by the subscapularis (anterior) and teres minor (posterior), below by the teres major, medially by the long head of the triceps brachii, and laterally by the humerus (surgical neck).

It then divides into an anterior and a posterior part. The anterior division supplies the deltoid (anterior and middle heads) while the posterior division supplies the teres minor and posterior part of deltoid
The posterior division terminates as the superior lateral cutaneous nerve of the arm

The inferior phrenic nerves are at the highest risk of damage as they are the first branches of the abdominal aorta. The potential space at the level of the diaphragmatic hiatus is a potentially useful site for aortic occlusion. However, leaving the clamp applied for more than 10 -15 minutes usually leads to poor outcomes.

The superior phrenic artery branches from the thoracic aorta.

The abdominal aorta begins at the level of the body of T12 near the midline, as a continuation of the thoracic aorta. It descends and bifurcates at the level of L4 into the common iliac arteries.

The branches of the abdominal aorta (with their vertebra level) are:
1. Inferior phrenic arteries: T12 (upper border)
2. Coeliac artery: T12
3. Superior mesenteric artery: L1
4. Middle suprarenal arteries: L1
5. Renal arteries: Between L1 and L2
6. Gonadal arteries: L2 (in males, it is the testicular artery, and in females, the ovarian artery)
7. Inferior mesenteric artery: L3
8. Median sacral artery: L4
9. Lumbar arteries: Between L1 and L4

The AV node has an intrinsic firing rate of 40-60 beats per minute which is clinically significant in cases of damage to the conducting pathways as patients continue to have a ventricular rate of 40-60. Patients who have an AV node supplied by the right coronary are said to be right dominant. The remaining 10% are left dominant and supplied by the left circumflex.

The right coronary artery supplies the right atrium, right ventricle, interatrial septum, and the inferior posterior third of the interventricular septum. It also supplies the atrioventricular node + sinoatrial node in most patients. The posterior descending artery supplies the posterior third of the interventricular septum.

The heart receives blood supply from coronary arteries. The right and left coronary arteries branch off the aorta and supply oxygenated blood to all heart muscle parts.

The left main coronary artery branches into:
1. Circumflex artery – supplies the left atrium, side, and back of the left ventricle. The left marginal artery arises from the left circumflex artery. It travels along the obtuse margin of the heart.
The left marginal artery, a branch of the circumflex artery, supplies the left ventricle.
2. Left Anterior Descending (LAD) artery – supplies the front and bottom of the left ventricle and front of the interventricular septum

The right coronary artery branches into:
1. Right marginal artery
2. Posterior descending artery

Campylobacter is the commonest bacterial cause of infectious intestinal disease in the UK. The majority of cases are caused by the Gram-negative bacillus Campylobacter jejuni which is spread by the faecal-oral route. The incubation period is 1-6 days.

Features include a prodrome phase with headaches and malaise, then diarrhoea occurs which is often bloody.
There is often abdominal pain which may mimic appendicitis.

It is usually self-limiting but treatment is warranted if the infection is severe or the infection occurs in an immunocompromised patient.
Severe infection comprises of high fever, bloody diarrhoea, or more than eight stools per day or symptoms last for more than one week.
This management would include antibiotics and the first-line antibiotic is clarithromycin.
Ciprofloxacin is an alternative but there are strains with decreased sensitivity to ciprofloxacin which can be frequently isolated.

Complications include:
1.Guillain-Barre syndrome may follow Campylobacter
2. Jejuniinfections
3. Reactive arthritis
4. Septicaemia, endocarditis, arthritis

The level of statistical significance required influences the sample size used. This is because sample size is used in the calculation of SD/SE.

Sample size does not affect

The level of acceptance
The alternative hypothesis with a general level set at p<0.05
The test to be used.

Experience of the investigator and the type of patient recruited should have no bearing on the required sample size.

Epoprostenol has a half-life of only 42 seconds and has rapid offset. It is used for the treatment of pulmonary hypertension.

Aspirin inhibits the COX enzyme irreversibly. It inhibits thromboxane synthesis but does not inhibit the enzyme thromboxane synthetase.

Ticlopidine, clopidogrel and prasugrel act as irreversible antagonists of P2 Y12 receptor of Adenosine Diphosphate (ADP). These drugs interfere with the activation of platelets by ADP and fibrinogen. Both aspirin and clopidogrel act irreversibly so they are not correct.

Paclitaxel is a long-acting antiproliferative agent used for the prevention of restenosis (recurrent narrowing) of coronary and peripheral stents and is not the correct answer.

Tirofiban has the next shortest duration of action after epoprostenol. If epoprostenol is not given in the question, it would be the best answer.

Peak expiratory flow rate (PEFR) is the maximum speed of air flow generated during a single forced exhaled breath. It is most useful when expressed as a percentage of the best value obtained from the patient.

Forced expiratory volume over 1 second (FEV1) is a lung parameter measured using spirometry. It is the amount of air forced out of the lung in one exhaled breath. It is a more accurate measure of lung obstructions as it doesn’t rely on effort like PEFR

PEFR and FEV1 are usually similar, but become more different in asthmatic patients as airflow becomes increasingly obstructed.

Acute severe asthma is most often diagnosed on history taking and examinations:

Respiratory rate: >25 breaths/min
Heart rate: >110 beats/min
PEFR: 33 – 50% predicted (<200L/min)
Patient state: Unable to complete a sentence in a single breath.

A chest x-ray is not routinely required, and is only indicated in specific circumstances, which are:

If a pneumomediastinum or pneumothorax is suspected
Possible life threatening asthma
Possible consolidation
Unresponsive asthma
If ventilation is required.

An echocardiograph (ECG) is not necessary in this case

Routine haematological and biochemical investigations are not urgent in this case as any abnormalities they detect will be secondary to the patient’s presentation.

An arterial blood gas (ABG) will only be indicated if SPO2 was <92% or if patient presented with life threatening symptoms.

The half life of Retinol binding protein (RBP) is 10-12 hours and therefore reflects more acute changes in protein metabolism than any of these proteins. Therefore it is not commonly used as a parameter for nutritional assessment.

The half life of Transthyretin (thyroxine binding pre-albumin) is only one to two days and so levels are less sensitive and this protein is not an albumin precursor. 15 mg/dL represents early malnutrition and a need for nutritional support.

Albumin levels have been frequently as a marker of nutrition but this is not a very sensitive marker. It’s half life more than 30 days and significant change takes some time to be noticed. Also, synthesis of albumin is decreased with the onset of the stress response after burns. Unrelated to nutritional status, the synthesis of acute phase proteins increases and that of albumin decreases.

A more accurate indicator of protein stores is transferrin. It’s response to acute changes in protein status is much faster. The half life of serum transferrin is shorter (8-10 days) and there are smaller body stores than albumin. A low serum transferrin level is below 200 mg/dL and below 100 mg/dL is considered severe. Serum transferrin levels can also affect serum transferrin level.

Fibronectin is used a nutritional marker but levels decrease after seven days of starvation. It is a glycoprotein which plays a role in enhancing the phagocytosis of foreign particles.

The Wolff-Parkinson-White syndrome (WPWS) is linked to an additional electrical conduction pathway between the atria and ventricles. This accessory pathway (bundle of Kent), unlike the atrioventricular (AV) node, is incapable of slowing down a rapid rate of atrial depolarization. In other words, a short circuit bypasses the AV node. Patients with a rapid ventricular response or narrow complex AV re-entry tachycardia are more likely to develop atrial fibrillation or flutter.

Digoxin can promote impulse transmission through this accessory pathway if a patient with WPWS develops atrial fibrillation because it works by blocking the AV node. This can cause ventricular fibrillation and an extremely rapid ventricular rate. As a result, it’s not advised.

Adenosine, beta-blockers, and calcium channel blockers, among other drugs that interfere with AV nodal conduction, are also generally contraindicated.

The class III antiarrhythmic drugs amiodarone and ibutilide (K+ channel block) and procainamide (Na+ channel block) are the drugs of choice.

The null hypothesis states that there is no significant difference between two groups.

The alternative hypothesis states that there is a significant difference between two groups.

A type I error (false positive) occurs when a null hypothesis is rejected when it should be accepted.

A type II error (false negative) occurs when the alternative hypothesis is rejected when it should be accepted.

The probability determines the rejection of a null hypothesis.

The level of significance is set at p <0.05.

Certain skeletal muscles are more resistant to the effects of neuromuscular blocking agents, both non-depolarizing and depolarizing. The diaphragm is the most resistant. The muscles of the larynx and the corrugator supercilii are less resistant. The abdominal, orbicularis oris, and limb peripheral muscles are the most sensitive muscles.

Twitch stimulation patterns:

Supramaximal single stimulus:

The frequency ranges from 1 Hz to 0.1 Hz (one every second to one every 10 seconds)
The response is proportional to the frequency of the event.
It has limited clinical utility because it only tells you whether or not a patient is paralysed (no information on degree of paralysis).

Over the course of 0.5 seconds (2 Hz), four supramaximal stimulate were applied:

It is possible to see ‘fade’ and use it as a basis for evaluation.
This stimulation pattern is used to determine the degree of blockade (1-2 twitches is appropriate for abdominal surgery)
If the train of four (TOF) count is 1-2, reversal agents can be used in conjunction with medium-acting neuromuscular blocking agents.

Ratio of TOF:

This is the ratio of the 4th twitch amplitude to the 1st twitch amplitude.
The ratio decreases with non-depolarising block and is inversely proportional to the degree of block, allowing objective measurement of residual neuromuscular blockade.
To achieve adequate reversal, the ratio (as measured by accelerography) must be between 0.7 and 0.9.

Count of twitches after a tetanic experience(PTC):

50 Hz for 5 seconds, then a 3 second pause, followed by a single 1 Hz twitch stimulus.
When the TOF count is zero, this stimulation pattern is used to assess deep blockade (that is, in neurosurgery, microsurgery or ophthalmic surgery when even small movements of a patient will disturb the surgical field)
It gives an estimate of how long it will take for the response to return to single twitches, allowing assessment of blocks that are too deep for any other technique.
A palpable post-tetanic count (PTC) of 2 indicates no twitch response for about 20-30 minutes, and a PTC of 5 indicates no twitch response for about 10-15 minutes.

This is without a doubt the best way to keep track of paralysis in patients who need to avoid diaphragmatic movement. It’s best to use drug infusions and aim for a PTC of 2. After a tetanic stimulus, acetylcholine is mobilised, causing post-tetanic potentiation.

Stimulation in Two Bursts:

750 milliseconds between two short bursts of 50 Hz
This stimulation pattern is used to assess small amounts of residual blockade manually (tactile).

Thermodilution is the most common dilution method used to measure cardiac output (CO) in a hospital setting.

During the procedure, a Swan-Ganz catheter, which is a specialized catheter with a thermistor-tip, is inserted into the pulmonary artery via the peripheral vein. 5-10mL of a cold saline solution with a known temperature and volume is injected into the right atrium via a proximal catheter port. The solution is cooled as it mixes with the blood during its travel to the pulmonary artery. The temperature of the blood is the measured by the catheter and is profiled using a computer.

The computer also uses the profile to measure cardiac output from the right ventricle, over several measurements until an average is selected.

Cardiac output changes at each point of respiration, therefore to get an accurate measurement, the same point during respiration must be used at each procedure, this is usually the end of expiration, that is the end-expiratory pause.

Refractometers measure the degree to which the light changes direction, called the angle of refraction. A refractometer takes the refraction angles and correlates them to refractive index (nD) values that have been established. Using these values, you can determine the concentrations of solutions.

During fetal development, blood oxygenated by the placenta flows to the foetus through the umbilical vein, bypasses the fetal liver through the ductus venosus, and returns to the fetal heart through the inferior vena cava.

Blood returning from the inferior vena cava then enters the right atrium and is preferentially shunted to the left atrium through the patent foramen ovale. Blood in the left atrium is then pumped from the left ventricle to the aorta. The oxygenated blood ejected through the ascending aorta is preferentially directed to the fetal coronary and cerebral circulations.

Deoxygenated blood returns from the superior vena cava to the right atrium and ventricle to be pumped into the pulmonary artery. Fetal pulmonary vascular resistance (PVR), however, is higher than fetal systemic vascular resistance (SVR); this forces deoxygenated blood to mostly bypass the fetal lungs. This poorly oxygenated blood enters the aorta through the patent ductus arteriosus and mixes with the well-oxygenated blood in the descending aorta. The mixed blood in the descending aorta then returns to the placenta for oxygenation through the two umbilical arteries.

The subclavian artery and vein have a similar path throughout their course, with the subclavian vein running anterior to the subclavian artery. The artery and vein are separated by the insertion of the scalenus anterior muscle.

There are three scalene muscles, found on each side of the neck:
1. Anterior scalene
2. Middle scalene
3. Posterior scalene

The scalenus anterior muscle is the anterior most of the three scalene muscles. It originates from the transverse processes of vertebrae C3-C6 and is inserted in the first rib.

Interleukin-4 is a cytokine which acts to regulate the responses of B and T cells.

Erythropoietin is responsible for the signal that initiated red blood cell production.

Granulocyte-colony stimulating factor stimulates the bone marrow to produce granulocytes.

Interleukin-5 is a cytokine that stimulates the proliferation and activation of eosinophils.

Thrombopoietin is the primary signal responsible for megakaryocyte and thus platelet production.
Platelets are also called thrombocytes. They, like red blood cells, are also derived from myeloid stem cells. The process involves a megakaryocyte developing from a common myeloid progenitor cell. A megakaryocyte is a large cell with a multilobulated nucleus, this grows to become massive where it will then break up to form platelets.

Immune cells are generated from haematopoietic stem cells in bone marrow. They generate two main types of progenitors, myeloid and lymphoid progenitor cells, from which all immune cells are derived.

The Delphi method relies on expert consensus. This method kicks off with an open ended questionnaire and uses its responses as a survey instrument for the next round in which each of the participants is asked to rate the items that the investigators have summarized on the basis of the data collected in the first round. Any disagreement is further discussed in phases to come on the basis of information obtained from previous phases.

Carotid endarterectomy is the procedure to relieve an obstruction in the carotid artery by opening the artery at its origin and stripping off the atherosclerotic plaque with the intima. This procedure is performed to prevent further episodes, especially in patients who have suffered ischemic strokes or transient ischemic attacks.

The external carotid artery terminates by dividing into the superficial temporal and maxillary branches. The maxillary artery is the larger of the two terminal branches and arises posterior to the neck of the mandible.

The other arteries mentioned in the answer options branch off from the following:
Temporal arteries from the maxillary artery
Middle meningeal artery from the maxillary artery
Lingual artery from the anterior aspect of the external carotid artery
Facial artery from the anterior aspect of the external carotid artery

Her symptoms are suggestive of trigeminal neuralgia which is a short, sudden, severe sharp unilateral pain in the facial region. The pain often follows the sensory distribution of the trigeminal nerve (CN V).

The trigeminal nerve gives rise to 3 sensory and 1 motor nuclei. Neuralgia can arise from any of the 3 sensory divisions.

The ophthalmic division gives rise to 3 further sensory branches, which are the frontal, lacrimal and nasociliary.

The frontal branch of the ophthalmic division of the trigeminal nerve is responsible for the innervation of the area in question.

The superior alveolar dental, zygomatic and sphenopalatine nerves are all branches arising from the maxillary division of the trigeminal nerve.

The mandibular division of the trigeminal nerve provides sensory and motor innervation. The sensory innervation is carried out by the auriculotemporal nerve which supplies the lower third of the face, while the motor fibres are responsible for controlling the muscles of mastication.

The somatic sensory branches of the vagus nerve are responsible for sensory innervation of the external acoustic meatus and tympanic membrane.

Compliance of the respiratory system describes the expandability of the lungs and chest wall. There are two types of compliance: dynamic and static.

Dynamic compliance describes the compliance measured during breathing, which involves a combination of lung compliance and airway resistance. Defined as the change in lung volume per unit change in pressure in the presence of flow.

Static compliance describes pulmonary compliance when there is no airflow, like an inspiratory pause. Defined as the change in lung volume per unit change in pressure in the absence of flow.

For example, if a person was to fill the lung with pressure and then not move it, the pressure would eventually decrease; this is the static compliance measurement. Dynamic compliance is measured by dividing the tidal volume, the average volume of air in one breath cycle, by the difference between the pressure of the lungs at full inspiration and full expiration. Static compliance is always a higher value than dynamic

Static compliance can be computed using the formula:

Cstat = Tidal volume/Plateau pressure – PEEP

Substituting the values given,

Cstat = 800/50-10
Cstat = 20 ml/cmH2O

Barbituric acid is the barbiturates’ pharmacologically inactive precursor. A pyrimidine heterocyclic nucleus is formed by the condensation of urea and malonic acid. Its pharmacological activity can be influenced by minor structural changes (structure function relationship).

The duration of action and potency as a sedative are influenced by the length of the side chains at C5. Barbiturates with three carbon atoms in their chain last longer than those with two. Anticonvulsant properties are enhanced by branched chains.

The addition of a methyl group at N1 causes a faster onset/offset of action, but it also causes excitatory phenomena (twitching/lower convulsive threshold).

The addition of oxygen and sulphur to C2 increases the molecule’s lipid solubility and thus its potency. Thiopentone (thiobarbiturate) has sulphur groups at C2, making it 20-200 times more lipid soluble than oxybarbiturates.

Bernoulli’s principle states that as the speed of a moving fluid increases, there is a simultaneously decrease in static pressure or a decrease in the fluid’s potential energy.
This is seen in the simultaneous increase in speed and kinetic energy and fall in pressure that causes entrainment of large volumes of air into a flow of 100% oxygen in the nozzle of HAFOE masks.

The reduction in fluid pressure that happens when a fluid flows through a constriction in a tube is the Venturi effect.

When a flow of gas or liquid attaches itself to a nearby surface and remains attached even when the surface curves away from the initial direction of flow, this is the Coanda effect.

The branch of engineering and technology that is concerned with the building of devices that use the flow and pressure of a fluid for functions usually performed by electronic devices is Fluidics . Fluidic logic is used to power some ventilators.

The branch of engineering that utilises pressurised gases is Pneumatics.

A single chamber pacemaker was implanted in the patient. In VVI mode, a pacemaker paces and senses the ventricle while being inhibited by a perceived ventricular event. The most likely electrical hazard from diathermy is electromagnetic interference (EMI).

EMI has the potential to cause the following: Inhibition of pacing
Asynchronous pacing
Reset to backup mode
Myocardial burns, and
Trigger VF.

Diathermy entails the implementation of high-frequency electrical currents to produce heat and either make incisions or induce coagulation. Monopolar cautery involves disposable cautery pencils and electrosurgical diathermy units. In typical monopolar cautery, an electrical plate is placed on the patient’s skin and acts as an electrode, while the current passes between the instrument and the plate. Monopolar diathermy can therefore interfere with implanted metal devices and pacemaker function.

Bipolar diathermy, where the current passes between the forceps tips and not through the patient and is less likely to generate EMI.

Whilst the presence of a CVP line may in theory predispose the patient to microshock, the use of prerequisite CF electrical equipment makes this very unlikely. The presence of a CVP line and pacemaker does not therefore unduly increase the risk of an electrical hazard.

Isolating transformers are used to protect secondary circuits and individuals from electrical shocks. There is no step-up or step-down voltage (i.e. there is a ratio of 1 to 1 between the primary and secondary windings).

A ground (or earth) wire is normally connected to the metal case of an operating table to protect patients from accidental electrocution. In the event that a fault allows a live wire to make contact with the metal table (broken cable, loose connection etc.) it becomes live. The earth will provide an immediate path for current to safely flow through and so the table remains safe to touch. Being a low resistance path, the earth lets a large current flow through it when the fault occurs ensuring that the fuse or RCD will quickly blow. Without an operating table earth, the patient is not at more risk of an electrical hazard because of the pacemaker.

There are two types of defibrillators
AC defibrillator
DC defibrillator

AC defibrillator,
consists of a step-up transformer with primary and secondary winding and two switches. Since secondary coil consists of more turns of wire than the primary coil, it induces larger voltage. A voltage value ranging between 250V to 750V is applied for AC external defibrillator. And used to enable the charging of a capacitor.

DC defibrillator,
consists of auto transformer T1 that acts as primary of the high voltage transformer T2. Is an iron core that transfers energy between 2 circuits by electromagnetic induction. Transformers are used to isolate circuits, change impedance and alter voltage output. transformers do not convert AC to DC.

Diode rectifier composed of 4 diodes made of semiconductor material allows current to flow only in one direction. Alternating current (AC) passing through these diodes produces direct current (DC). Capacitor stores the charge in the form of an electrostatic field.

Capacitor is used to convert the rectified AC voltage to produce DC voltage but capacitors do not directly convert AC to DC.

Inductor induces a counter electromotive force(emf) that reduces the capacitor discharge value.

In step-down transformer primary coils has more turns of wire than secondary coil, so induced voltage is smaller in the secondary coil.

The duodenojejunal flexure is the point where the duodenum becomes the jejunum.

The ligament of Treitz, which arises from the right crus of diaphragm, provides suspension for support.

Between the ileum and the caecum is the ligament of Treves.

Nitric oxide is generated from L-arginine by nitric oxide synthase. It is produced in response to haemodynamic stress by the vascular endothelium, and it produces both smooth muscle relaxation and reduced vascular resistance.

Nitric oxide may be inactivated through interaction with other oxygen free radicals, (e.g. oxidised low-density lipoprotein (LDL)).

Nitric oxide causes the production of the second messenger, cyclic guanosine monophosphate (cGMP).

Ampicillin belongs to the family of penicillin. Resistance to this group of drugs is due to ?-lactamase production which opens the ?-lactam ring and inactivates Penicillin G and some closely related congeners. The majority of Staphylococci and some strains of gonococci, B. subtilis, E. coli, and a few other bacteria produce penicillinase.

Resistance to cephalosporins is due to changes in penicillin-binding proteins.

Resistance to macrolides are due to post-transcriptional methylation of 23s bacterial ribosomal RNA

Resistance to fluoroquinolones is due to mutations in DNA gyrase.

Paediatric life support differs from adult life support in that hypoxia is the primary cause of deterioration.

After checking for danger, the child should be given a gentle stimulus (such as holding the head and shaking the arm) and asked, Are you alright? according to current advanced paediatric life support (APLS) guidelines. Safety, Stimulate, Shout is a phrase that is frequently remembered. Any airway assessment should be preceded by these actions.

Although the algorithm includes five rescue breaths, they are performed after the airway assessment.

It is not recommended to ask parents to leave unless they are obstructing the resuscitation. A team member should be with them at all times to explain what is going on and answer any questions they may have.

CPR should not begin until the child has been properly assessed and rescue breaths have been administered.

An epidemic is declared when the increase in a give disease is above a certain level in a specific interval of time.

An endemic is the general, usual level of a disease in a population at a particular time.

A pandemic is an epidemic that is spread across many countries and continents.

Breathing 100% oxygen for three minutes will provide the best reservoir of oxygen during apnoea by oxygenating the functional residual capacity (FRC).

Sitting at 45 degrees might increase the FRC and improve oxygen reserve but not compared with 100% oxygenation.

The following table compares the oxygen reserves in the body following pre-oxygenation with room air and 100% oxygen:

Compartment Factors Room air (mL) 100% O2 (mL)
Lung FAO2, FRC 630 2850
Plasma PaO2, DF, PV 7 45
Red blood cells Hb, TGV, SaO2 788 805
Myoglobin – 200 200
Interstitial space – 25 160

FAO2 = alveolar fraction of oxygen.
FRC = Functional residual capacity.
PaO2 = partial pressure of oxygen dissolved in arterial blood
DF = dissolved form.
PV = plasma volume.
TG = total globular volume .
Hb = haemoglobin concentration.
SaO2 = arterial oxygen saturation

Stopping smoking one month prior to surgery will not be more effective than pre-oxygenation with 100% oxygen though it may reduce postoperative pulmonary complications. Note that both long term and short term abstinence reduces pulse rate and blood pressure thus reducing oxygen consumption and also reduce carboxyhaemoglobin levels.

Blood transfusion will not make a big difference in oxygen reserve, particularly if a blood transfusion is administered within 12-24-hours before surgery.

Heliox (79% helium and 21% oxygen) despite its lower viscosity is unlikely to be more effective than 100% oxygen .

With regards to the autonomic nervous system (ANS)

1. It is not under voluntary control
2. It uses reflex pathways and different to the somatic nervous system.
3. The hypothalamus is the central point of integration of the ANS. However, the gut can coordinate some secretions and information from the baroreceptors which are processed in the medulla.

With regards to the central nervous system (CNS)
1. There are myelinated preganglionic fibres which lead to the
ganglion where the nerve cell bodies of the non-myelinated post ganglionic nerves are organised.
2. From the ganglion, the post ganglionic nerves then lead on to the innervated organ.

Most organs are under control of both systems although one system normally predominates.

The nerves of the sympathetic nervous system (SNS) originate from the lateral horns of the spinal cord, pass into the anterior primary rami and then pass via the white rami communicates into the ganglia from T1-L2.

There are short pre-ganglionic and long post ganglionic fibres.
Pre-ganglionic synapses use acetylcholine (ACh) as a neurotransmitter on nicotinic receptors.
Post ganglionic synapses uses adrenoceptors with norepinephrine / epinephrine as the neurotransmitter.
However, in sweat glands, piloerector muscles and few blood vessels, ACh is still used as a neurotransmitter with nicotinic receptors.

The ganglia form the sympathetic trunk – this is a collection of nerves that begin at the base of the skull and travel 2-3 cm lateral to the vertebrae, extending to the coccyx.

There are cervical, thoracic, lumbar and sacral ganglia and visceral sympathetic innervation is by cardiac, coeliac and hypogastric plexi.

Juxta glomerular apparatus, piloerector muscles and adipose tissue are all organs under sole sympathetic control.

The PNS has a craniosacral outflow. It causes reduced arousal and cardiovascular stimulation and increases visceral activity.

The cranial outflow consists of
1. The oculomotor nerve (CN III) to the eye via the ciliary ganglion,
2. Facial nerve (CN VII) to the submandibular, sublingual and lacrimal glands via the pterygopalatine and submandibular ganglions
3. Glossopharyngeal (CN IX) to lungs, larynx and tracheobronchial tree via otic ganglion
4. The vagus nerve (CN X), the largest contributor and carries ¾ of fibres covering innervation of the heart, lungs, larynx, tracheobronchial tree parotid gland and proximal gut to the splenic flexure, liver and pancreas

The sacral outflow (S2 to S4) innervates the bladder, distal gut and genitalia.

The PNS has long preganglionic and short post ganglionic fibres.
Preganglionic synapses, like in the SNS, use ACh as the neuro transmitter with nicotinic receptors.
Post ganglionic synapses also use ACh as the neurotransmitter but have muscarinic receptors.

Different types of these muscarinic receptors are present in different organs:
There are:
M1 = pupillary constriction, gastric acid secretion stimulation
M2 = inhibition of cardiac stimulation
M3 = visceral vasodilation, coronary artery constriction, increased secretions in salivary, lacrimal glands and pancreas
M4 = brain and adrenal medulla
M5 = brain

The lacrimal glands are solely under parasympathetic control.

A nominal volume of 2 litres is contained in a CD cylinder. It has a pressure of 230 bar when full and contains litres 460 L of useable oxygen at STP.

For every 1000 mL 100% oxygen there will be an entrainment of 1000 mL or air (20% oxygen) in an air/oxygen mix.

The average concentration is, therefore, 120/2=60% or 0.6.

Microshock refers to ventricular fibrillation caused by miniscule amounts of currents or voltages (100-150 microamperes) passing through the myocardial tissue from external cables arising from electrical components within the cardiac muscle, for example, pacemaker electrodes or saline filled venous catheters.
The risk of shock changes with the construction of electrical equipment in question. The main classes of electrical equipment include: I: Appliances have a protective earth connected to an outer casing which prevents live elements from coming in contact with conductive elements. A fault in this equipment class will result in live elements coming in contact with the outer casing and allowing electrical flow into the protective earth. This triggers the protective fuse to disconnect the electric supply to the appliance.
II: These appliances have reinforced insulation. In the event of a fault which causes the first layer of insulation to fail, the second layer is able to prevent contact of live elements with outer casing.
III: These appliances have no insulation to provide safety, and rely solely on the use of separated extra low voltage source (SELV) which limits voltage to 25V AC or 60V DC allowing for a person to come in contact with it without risk of a shock under normal dry conditions. Under wet conditions, voltage supply should be lowered to reduce risk of shock. These devices have no risk of macroshocks, but some risk of microshocks.
Class I and II electrical appliances are further divided into subtypes developed to limit current leakage in the event of a singular fault:
B (body): Upper limit of current leakage is 500 µA. This current can cause skin tingling and microshocks, but is not sufficient to cause injury.
BF (body floating): These appliances have an isolating capacitor or transformer which separate the secondary circuit from the protective earth. The upper limit of current leakage is the same as type B.
CF (cardiac floating): Upper limit of leakage current during a singular fault is 50 microamps. It is least likely to result in a microshock

The internal laryngeal nerve provides sensory innervation to the laryngeal mucosa, and injury to it will cause loss of sensation.

The internal laryngeal nerve lies inferior to the piriform recess mucous membrane, placing it at high risk of irritation or damage by objects which become lodged in the recess.

The internal laryngeal artery branches off the superior laryngeal artery accompanied by the superior laryngeal nerve, inferior to the thyroid artery which branches off the superior thyroid artery close to its bifurcation from the external carotid artery.

Standard error can be calculated by the following formula:
Standard Error= (Standard Deviation)/√(Sample Size)
= (16) / √(100)
= 16 / 10
= 1.6

During carotid endarterectomy, injury to the vagus nerve or its branches can cause hoarseness. Injury to the vagus nerve can result in adductor vocal cord paralysis. It can also cause other symptoms like dysphagia or even vocal cord immobility.

Carotid endarterectomy is the procedure to relieve an obstruction in the carotid artery by opening the artery at its origin and stripping off the atherosclerotic plaque with the intima. Because of the internal carotid artery relations, there is a risk of cranial nerve injury during the procedure involving one or more of the following nerves: CN IX, CN X (or its branch, the superior laryngeal nerve), CN XI, or CN XII.

However, only damage to the vagus would account for speech difficulties.

It’s a minute volume divider – True
The Manley MP3 ventilator is classed as a minute volume divider. The entire fresh gas flow or minute volume is delivered to the patient, having been divided into readily set tidal volumes.

Can efficiently ventilate patients with poor pulmonary compliance – False
Ventilating patients with poor pulmonary compliance is not easily achieved, which makes it an unsuitable ventilator for a modern ICU.

Can generate tidal volume up to 1500ml – False
It can generate tidal volumes up to 1000 ml (not 1500 ml), and the inflation pressure can be adjusted by sliding a weight along a rail.

Functions like a Mapleson A system during spontaneous ventilation – False
The ventilator functions like a Mapleson D breathing system (not Mapleson A) during spontaneous ventilation.

Has three sets of bellows – False
The fresh gas flow drives the ventilator which allows rapid detection of gas supply failure. It has two sets of bellows (not three) and three unidirectional valves.

A stock dose of Intravenous paracetamol available in the market is 10mg/ml. There is a recommended dose of IV paracetamol according to the profile of the patient (age, co-morbidities, weight).

Weight Recommended Dose Maximum per day
≤10 kg 7.5 mg/kg 30 mg/kg
>10 kg to ≤33 kg 15 mg/kg 60 mg/kg (not exceeding 2 g)
>33 kg to ≤50 kg 15 mg/kg 60 mg/kg (not exceeding 3 g)
>50 kg with additional risk factors for hepatotoxicity 1g 3 g
>50 kg with no additional risk factors for hepatotoxicity 1g 4 g

Special precaution must be observed for patients with hepatocellular insufficiency. The maximum dose per day should not exceed 3g.

The epiploic foramen (foramen of Winslow or aditus to the lesser sac) is found behind the free right border of the lesser omentum. A short, 3 cm slit serves as the entrance to the lesser sac from the greater sac.

The epiploic foramen has the following boundaries:
Anteriorly: hepatoduodenal ligament, the bile duct (anteriorly on the right), the hepatic artery (anteriorly on the left), and the portal vein (posteriorly) together with nerves and lymphatics
Superiorly: the peritoneum of the posterior layer of the hepatoduodenal ligament runs over the caudate process of the liver
Posteriorly: inferior vena cava
Floor: upper border of the first part of the duodenum
The anterior and posterior walls of the foramen are normally
apposed, which partly explains why patients can develop large fluid
collections isolated to the greater or lesser sac

Rapid control of the hepatic artery and portal vein can be obtained by compression of the free edge of the lesser omentum (a ‘Pringle’ manoeuvre), which is a potentially useful technique in liver trauma and surgery.

Magnesium is a unique calcium antagonist as it can act on most types of calcium channels in vascular smooth muscle and as such would be expected to decrease intracellular calcium. One major effect of decreased intracellular calcium would be inactivation of calmodulin-dependent myosin light chain kinase activity and decreased contraction, causing arterial relaxation that may subsequently lower peripheral and cerebral vascular resistance, relieve vasospasm, and decrease arterial blood pressure.

The vasodilatory effect of MgSO4 has been investigated in a wide variety of vessels. For example, both in vivo and in vitro animal studies have shown that it is a vasodilator of large conduit arteries such as the aorta, as well as smaller resistance vessels including mesenteric, skeletal muscle, uterine, and cerebral arteries.

The theory of cerebrovascular vasospasm as the aetiology of eclampsia seemed to be reinforced by transcranial Doppler (TCD) studies which suggested that MgSO4 treatment caused dilation in the cerebral circulation as well as in animal studies that used large cerebral arteries.

The following units are derived SI units of measurement.

Energy or work: kg.m2.s-2
The Joule (J) is the energy transferred to an object when a force of one newton acts on that object in the direction of its motion through a distance of one meter or N.m.

Power: kg.m2.s-3
The Watt (W) = rate of transfer of energy or Joule per second J/s.

Force: kg.m.s-2
One Newton (N) which is the international unit of measure for force = 1 kilogram meter per second squared. 1 Newton of force is the force required to accelerate an object with a mass of 1 kilogram 1 meter per second per second.

Volt: kg.m2.s-3.A-1
The volt (V) is defined as the potential difference across a conductor when a current of one ampere dissipates one watt of power or W/A.

Pressure: kg.m-1.s-2
A pascal (Pa) is force per unit area or N/m2.

Due to an increased tidal volume with little change or slight increase in respiratory rate, Minute ventilation at term is increased by about 50%. Hypothalamic function are thought to influence by Progesterone, oestradiol and prostaglandins. This causes a mild compensated respiratory alkalosis.

Maternal PaCO2 is usually decreased to about 32 mmHg (4.27 kPa) as a result of this increased alveolar ventilation at term . A compensatory decrease in serum bicarbonate from 27 to 21 mmol/L by renal excretion lessens the impact of maternal alkalosis.

The central venous pressure (CVP) waveform depicts changes of pressure within the right atrium. Different parts of the waveform are:

A wave: which represents atrial contraction. It is synonymous with the P wave seen during an ECG. It is often eliminated in the presence of atrial fibrillation, and increased tricuspid stenosis, pulmonary stenosis and pulmonary hypertension.

C wave: which represents right ventricle contraction at the point where the tricuspid valve bulges into the right atrium. It is synonymous with the QRS complex seen on ECG.

X descent: which represents relaxation of the atrial diastole and a decrease in atrial pressure, due to the downward movement of the right ventricle as it contracts. It is synonymous with the point before the T wave on ECG.

V wave: which represents an increase in atrial pressure just before the opening of the tricuspid valve. It is synonymous with the point after the T wave on ECG. It is increased in the background of a tricuspid regurgitation.

Y descent: which represents the emptying of the atrium as the tricuspid valve opens to allow for blood flow into the ventricle in early diastole.

Prerenal failure has a serum urea: creatinine ratio of >100, while acute kidney injury has a ratio of 40.
In prerenal failure, ADH levels are typically high, resulting in water, urea, and sodium resorption. The fractional sodium excretion is less than 1%, but it is greater than 2% in acute tubular necrosis.
Prerenal azotaemia has higher serum urea nitrogen/serum creatinine ratios (>20), whereas acute tubular necrosis has lower ratios (10-15). The normal range is between 12 and 20.
Urinary sodium is less than 20 in prerenal failure and greater than 40 in acute tubular necrosis.
Prerenal failure has a urine osmolality of >500, while acute tubular necrosis has an osmolality of 350.
Prerenal failure has a urine/serum creatinine ratio of >40, while acute tubular necrosis has a urine/serum creatinine ratio of 20.

The concentrations of serum urea or creatinine change in inverse proportion to glomerular filtration. Changes in serum creatinine concentrations are more reliable than changes in serum urea concentrations in predicting GFR. Creatinine is produced at a constant rate from creatine, and blood concentrations are almost entirely determined by GFR.

A number of factors influence urea formation, including liver function, protein intake, and protein catabolism rate. Urea excretion is also influenced by hydration status, the amount of water reabsorption, and GFR.

A high serum creatinine level, as well as a urine output of less than 10 mL/hour and the production of concentrated looking urine, do not necessarily indicate a specific cause of oliguria.

When there is a fall in ionised plasma calcium levels, the chief cells of the parathyroid glands are stimulated to secrete parathyroid hormone (PTH).

50% of extracellular calcium occurs as non-ionised, protein- (albumin-)bound calcium.

The degree of ionisation increases with low ph and decreases with high pH.

There is increased renal calcium excretion with secretion of calcitonin.

The Weibull distribution are used to describe various types of observed failures of the components. it is used in reliability and survival analysis.

Regression Analysis is used to measure the relationship between among two or more variable. It determines the effect of independent variables on the dependent variables.

Student t-test is one of the most commonly used method to test the hypothesis. It determines the significant difference between the means of two different groups.

A time series is a collection of observations of well-defined data obtained at regular interval of time.

Kaplan-Meier estimator is used to estimate the survival function from lifetime data. It can be derived from maximum likelihood estimation of hazard function. It is most likely used to measure the fraction of patient’s life for a certain amount of time after treatment.

Dopamine (DA) is a dopaminergic (D1 and D2) as well as adrenergic ? and ?1 (but not ?2 )agonist.

The D1 receptors in renal and mesenteric blood vessels are the most sensitive: i.v. infusion of a low dose of DA dilates these vessels (by raising intracellular cyclic adenosine monophosphate).

Moderately high doses produce a positive inotropic (direct ?1 and D1 action + that due to NA release), but the little chronotropic effect on the heart.

Vasoconstriction (?1 action) occurs only when large doses are infused.

At doses normally employed, it raises cardiac output and systolic BP with little effect on diastolic BP. It has practically no effect on nonvascular ? and ? receptors; does not penetrate the blood-brain barrier – no Central nervous system effects.

Dopamine is less arrhythmogenic than adrenaline

Regarding dopamine part of the dose is converted to Noradrenaline in sympathetic nerve terminals.

Charles’ Law states that there is a direct correlation between temperature and volume, where pressure and amount gas are constant. As temperature increases, volume also increases.

Boyle’s Law states that Pressure is inversely proportional to volume, assuming that temperature and amount of gas are constant. As volume increases, pressure decreases. In Dalton’s law of partial pressure, the total pressure exerted by a mixture of gases is equal to the sum of the partial pressure of the gases in mixture.

According to Henry’s Law for concentration of dissolved gases, at a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid. An equivalent way of stating the law is that the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid.

Gay-Lussac’s Law states that the pressure of a given mass of gas varies directly with the absolute temperature of the gas, when the volume is kept constant. This law is very similar to Charles’ Law, with the only difference being the type of container. Whereas the container in a Charles’ Law experiment is flexible, it is rigid in a Gay-Lussac’s Law experiment.