The relative risk (also known as risk ratio [RR]) is the ratio of risk of an event in one group (e.g., exposed group) versus the risk of the event in the other group (e.g., nonexposed group).

The odds ratio (OR) is the ratio of odds of an event in one group versus the odds of the event in the other group.

The process used in the study is Delphi method. 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.

A pulse oximeter is a piece of medical equipment used as a non-invasive method of measuring the oxygen saturation of blood.

It works by measuring the ratio of absorption of red and infrared light in a section of blood flow, as red light is largely absorbed by deoxygenated blood, and infrared light is largely absorbed by oxygenated blood.

Pulse oximetry relies on photoplethysmography (PPG) waveforms. The oximeter has 2 sides, with different functions. One side houses light-emitting diodes which are responsible for transmitting 2 light wavelengths, 660nm for red light and 940nm for near infrared light. The other side is a photodetector. The light emitted travels through the body and the amount that is not absorbed is measured by the photodetector.

Smokers often have increased levels of carboxy haemoglobin (COHb). This leads to artificial increases in pulse oximeter readings as it is unable to differentiate between COHb and oxyhaemoglobin (O2HB) as they both absorb red light at 660nm. Every 1% increase of circulating carboxyhaemoglobin, results in a correlative 1% increase in oximeter readings.

Prilocaine toxicity will cause an artificial decrease in oximeter readings. This is because prilocaine metabolites cause methemoglobinemia (MetHB), which are dysfunctional haemoglobins unable to properly transport oxygen. In this case, a laboratory multiwavelength co-oximeter is recommended for a more accurate reading.

Anaemia will not affect oximeter readings as long as haemoglobins in the blood are normal.

Sickle cell disease does not affect oximeter readings despite its ability to cause hypoxia and shift the oxygen dissociation curve to the right.

Brown-red fingernail polish will cause an underestimation of pulse oximeter readings.

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.

The autonomic nervous system is divided into the sympathetic and parasympathetic nervous system. They are anatomically and physiologically different.

The sympathetic nervous system arises from the thoracolumbar outflow (T1-L5 ) at the lateral horns of grey matter of the spinal cord. Their preganglionic neurones are usually short myelinated and synapse in ganglia lateral to the vertebral column and have acetyl choline (Ach) as the neurotransmitter. Their postganglionic neurones are longer and unmyelinated and synapse with effector organ where the neurotransmitter is either adrenaline or noradrenaline.

The outflow of the parasympathetic nervous system is craniosacral. The cranial part originates from the midbrain and medulla (cranial nerves III, VII, IX and X) and the sacral outflow is from S2, S3 and S4. Their preganglionic neurones are usually long myelinated and synapse in ganglia close to the target organ and has Ach as its neurotransmitter. The unmyelinated postganglionic neurones is shorter and they synapse with effector organ. The neurotransmitter here is also Ach.

Both sympathetic and parasympathetic preganglionic neurons are cholinergic. Only the postganglionic parasympathetic neurons are cholinergic.

Level 1 – High-quality randomised controlled trial with statistically significant difference or no statistically significant difference but narrow confidence intervals (prospective controlled)

Level 2 – Prospective comparative study (prospective uncontrolled)

Level 3 – Case-control study, retrospective comparative study (retrospective controlled)

Level 4 – Case series (retrospective uncontrolled)

Level 5 – Expert opinion.

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.

30 mmol Na+ and 30 mmol Cl- are found in 1 litre of 0.18 percent N. saline with 4% dextrose. Percent (percent) refers to the number of grammes of a compound per 100 mL, so a litre of 4 percent dextrose solution contains 40 grammes.

As a result, a 500 mL bag of 1/5th N. saline and 4% dextrose contains approximately 15 mequivalents of sodium and 20 g of glucose. It is hypotonic due to its osmolarity of 284.

Because of the risk of hyponatraemia, it is no longer considered the crystalloid of choice for fluid maintenance in children.

The internal jugular vein is found on both sides of the neck and collects blood from the brain, superficial regions of the face, and neck. It drains into the right atrium.

It is a continuation of the sigmoid sinus and begins in the posterior cranial fossa and exits the skull via the jugular foramen.
It runs within the carotid sheath as it descends in the neck and is accompanied by the vagus nerve posteriorly and the common carotid anteromedially.

The hypoglossal nerve emerges from the hypoglossal canal medial to the internal carotid artery and the internal jugular vein and ninth, tenth, and eleventh cranial nerves.

The internal jugular vein crosses anterior to the thoracic duct on the left side.

The intrinsic pathway is best assessed by the aPTT time.

D-dimer is a fibrin degradation product which is raised in the presence of blood clots.

A 50:50 mixing study is used to assess if a prolonged PT or aPTT is due to factor deficiency or a factor inhibitor.

The thrombin time is a test used to assess fibrin formation from fibrinogen in plasma. Factors that prolong the thrombin time include heparin, fibrin degradation products, and fibrinogen deficiency.

Intrinsic pathway – Best assessed by APTT. Factors 8,9,11,12 are involved. Prolonged aPTT can be seen in haemophilia and use of heparin.

Extrinsic pathway – Best assessed by Increased PT. Factor 7 involved.

Common pathway – Best assessed by APTT & PT. Factors 2,5,10 involved.

Vitamin K dependent factors are factors 2,7,9,10

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

This is a classical case of unstable angina or NSTEMI (Non-ST-elevation myocardial infarction). As soon as the diagnosis of unstable angina or NSTEMI is made the initial treatment is Aspirin and antithrombin therapy.

Betablocker is known to reduce mortality from acute myocardial infarction by reducing oxygen demand. If there is no contraindication (heart block, bradycardia, hypotension, severe left ventricular dysfunction, and asthma), a beta-blocker should be given early. This patient has hypotension and therefore metoprolol is contraindicated.

If three doses of nitroglycerine tablets or Nitrolingual sprays and intravenous beta-blockers too cannot relieve the symptoms intravenous Glyceryl Trinitrate (GTN) should be considered provided that there is no hypotension. But in this case, the patient is hypotensive, and therefore, it is contraindicated.

If the symptoms are not relieved after three serial doses of nitroglycerine or if symptoms recur despite adequate anti-anginal treatment morphine sulphate is indicated.

The blood vessel well is divided into 3 parts, namely:

The tunica intima, which is the deepest layer. It contains endothelial cells separated by gap junctions

The tunica media, primarily consisting of the involuntary smooth muscle fibres, laid out in spiral layers with elastic fibres and connective tissue.

The tunica adventitia, which is the most superficial layer. It consists of the vasa vasorum, fibroblast and collagen.

Half life (T½) is the time required to change the amount of drug in the body by one-half (or 50%) during elimination. The time course of a drug in the body will depend on both the volume of distribution and the clearance.

Extrapolating the values from the plasma concentration vs time:

Plasma concentration at 0 hours = 800 mcg/mL
Plasma concentration at 2 hours = 400 mcg/mL
Plasma concentration at 4 hours = 200 mcg/mL
Plasma concentration at 6 hours = 100 mcg/mL
Plasma concentration at 8 hours = 50 mcg/mL
Plasma concentration at 10 hours = 25 mcg/mL
Plasma concentration at 12 hours = 12.5 mcg/mL
Plasma concentration at 14 hours = 6.25 mcg/mL

The most likely of the differential diagnosis in this case is a duodenal ulcer located on the posterior abdominal wall.

These can cause an erosion of the abdominal wall, eventually affecting the gastroduodenal artery and resulting in major bleeding and haematemesis.

Gastroduodenal artery supplies the pylorus, proximal part of the duodenum, and indirectly to the pancreatic head (via the anterior and posterior superior pancreaticoduodenal arteries)

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

30mL 0.5% bupivacaine, 1mL 1 in 1,000 adrenaline and 89mL 0.9% N. Saline is the correct answer.
Initial concentration of bupivacaine is 0.5% with a volume of 30mL

The volume is doubled (60mL) by the addition of 0.9% N. saline (30mls) and the concentration of bupivacaine is halved to (0.25%).

If the volume is doubled again (120mL) by the addition of further 0.9% N. saline (59mls) the final concentration of bupivacaine is halved again to 0.125%. Total N. saline = 89mls

The 1 mL of 1 in 1000 adrenaline has also been diluted into the final volume of 120 mL making it a 1 in 120000 concentration.

Monoamine oxidase (MOA) enzymes are responsible for the catalyses of monoamine oxidative deamination. It assists the degradation of serotonin, norepinephrine (NE) and dopamine.

They are found in the mitochondria of most central and peripheral nerve tissues.

There are 2 different types:

Type A: Whose main function it to inactivate dopamine, tyramine, norepinephrine and 5-hydroxytryptamine. In addition to the nervous system, it is also found in the liver, brain gastrointestinal tract, pulmonary endothelium and placenta
Type B: Whose main function is to inactivate dopamine, tyramine, tryptamine and phenylethylamine. In addition to the nervous system, it is also found in the liver, brain (especially in the basal ganglia) and blood platelets.

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.

An intercostal nerve block is used for therapeutic and diagnostic purposes. Intercostal nerve blocks manage acute and chronic pain in the chest area. Common indications are chest wall surgery and shingles or postherpetic neuralgia.

An intercostal nerve block is also an effective option for the management of pain associated with chest trauma and rib fractures. These blocks have been shown to improve oxygenation and respiratory mechanics, and offer pain relief that is comparable to that of epidural analgesia.

This technique, however, is limited by the relatively large doses of local anaesthetic required, and relatively high intravascular uptake from the intercostal space, increasing risk of local anaesthetic toxicity.

The extrinsic pathway is considered as the main pathway of coagulation cascade.

Heparin is known to inhibit the activation of coagulation factors 2,9,10, and 11.

The extrinsic and intrinsic pathways meet at the activation of coagulation factor 10.

Fibrinogen is converted into Fibrin in the presence of Thrombin. Plasminogen is converted into plasmin during fibrinolysis to breakdown fibrin clot.

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.

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.

The positive predictive value is the ratio of patients truly diagnosed as positive to all those who had positive test results. In this case, this is 60/(60+20)=75%.

The negative predictive value is the ratio of patients truly diagnosed as negative to all those who had negative test results. In this case, this is 80/(80+40)=67%.

The sensitivity is the ratio of patients with the disease who test positive i.e. true positive patients to the total number of people with the disease. In this case, this is 60/(60+40)=60%.

The specificity is the ratio of people who don’t have the disease who test negative i.e. true negatives to the total number of people without the disease. In this case, this is 80/(20+80)=80%.

70% is not the result of any screening measurements

The answer is anterior to the spermatic cord.

The inguinal canal in men contains the ilioinguinal nerve, the genitofemoral nerve and the spermatic cord.

The ilioinguinal nerve arises of the L1 nerve root with the Iliohypogastric nerve, before entering the inguinal canal from the side, through the muscles of the abdomen, travelling superficial to the spermatic cord.

Bell’s palsy is facial muscle weakness or paralysis that arises from idiopathic damage to the facial nerve. It can occur at any age but is commonly associated with some conditions:
1. pregnancy
2. diabetes
3. upper respiratory ailment
4. GBS
5. Toxins

The common symptoms of Bell’s palsy are:
1. Abnormal corneal reflex as the facial nerve controls the motor aspect of the corneal reflex.
2. The loss of control of facial muscles and eyelids leads to decreased tear production.
3. mild weakness to total paralysis on one side of the face, occurring within hours to days.
4. Bell’s palsy is a lower motor neuron lesion that usually spares the forehead while the upper motor near lesions, like stroke, involves the entire face.
5. The anterior two-thirds of the tongue is supplied by the chorda tympani branch of the facial nerve, thus resulting in loss of taste.
6. Ptosis can be a feature of Bell’s palsy but Bell’s palsy would typically show unilateral symptoms rather than bilateral.

BMR is lower in females than males.

It decreases with increasing age.

There is an increase in BMR with increased muscle (i.e. lean tissue)

BMR is increased in stress and illness. There is also an catabolic state in these conditions.

Every surgical procedure is associated with a stress response which comprises a number of endocrine, metabolic, and immunological changes triggered by neuronal activation of the hypothalamic-pituitary-adrenal axis. The overall metabolic effect of the stress response to surgery includes an increase in secretion of catabolic hormones, such as cortisol and catecholamine, and a decrease in secretion of anabolic hormones, such as insulin and testosterone. The increase in levels of catabolic hormones in plasma stimulates glucose production, and there is a relative lack of insulin together with impaired tissue insulin sensitivity and glucose utilization, which is called insulin resistance. Consequently, blood glucose concentrations will increase, even in the absence of pre-existing diabetes.

A study compared the effects of spinal and general anaesthesia on changes in blood glucose concentrations during surgery in nondiabetic patients. Although mean blood glucose concentrations showed a significant proportional increase during surgery in both groups, this effect was much more significant with general anaesthesia than with spinal anaesthesia. These results indicate that spinal anaesthesia is more effective than general anaesthesia in attenuating the hyperglycaemic response to surgery.

The common peroneal (fibular) nerve is a peripheral nerve in the lower limb. It arises of the L4-S2 nerve roots and has sensory and motor innervations:

Sensory: Provides innervation of the lateral leg and foot dorsum.

Motor: Provides innervation of the short head of the biceps femoris, as well as muscles of the anterior and lateral leg compartments.

It is the most commonly damaged nerve in the lower extremity, as it is easily compressed by a plaster cast or injured when the fibula is fractured.

Damage to the common peroneal nerve will result in loss of dorsiflexion at ankle (footdrop, as feet are permanently plantarflexed), with the accompanying high stepping gait.

The saphenous and sural nerve only provide sensory innervation.

The tibial nerve arises from the sciatic nerve (like the common peroneal), but it provides motor innervation to the posterior leg compartments and intrinsic foot muscles. Injury to the tibial nerve will cause loss of plantar flexion, toe flexion and weakened foot inversion.

Extreme hip flexion into the lithotomy or Lloyd-Davies position can result in stretch damage to the neurones (sciatic and obturator nerves) or by applying direct pressure (femoral nerve compression).

The surface marking for locating the femoral artery is the mid-inguinal point, which is the halfway point between the anterior superior iliac spine (ASIS) and the pubic symphysis.

The other mentioned options are not specific for any landmark.

However, it is important to note the difference between the mid inguinal point and the midpoint of the inguinal ligament, which is travels from the ASIS to the pubic tubercle.

An agonist is a molecule with intrinsic efficacy and affinity for a receptor. The ability of a drug-receptor interaction to produce a maximal response is referred to as intrinsic efficacy or activity. Efficacy also refers to a drug’s ability to have a therapeutic or beneficial effect. Although the potencies of morphine and fentanyl differ, they both have the same intrinsic efficacy.

The amount of drug required to produce a given effect is referred to as potency. If drug X is effective in a dose of 100 mcg, its potency is greater than if drug Y is effective in a dose of 10 mg.

The therapeutic index, also known as the margin of safety, is a ratio of the lethal or serious side effect dose of a drug divided by the therapeutic dose of the same drug.

The term bioavailability refers to the ability of a substance to be absorbed. The area under a curve (AUC) of a graphic plot of plasma concentration and time is used to calculate oral bioavailability. It’s used to figure out how much of a drug to take and when to take it.

Rifampicin is a potent inducer of liver cytochrome enzymes. Other enzyme inducers are:
Carbamazepine
Sodium valproate
Phenytoin
Phenobarbitone

Noradrenaline also called norepinephrine belongs to the catecholamine family that functions in the brain and body as both a hormone and neurotransmitter.

They have sympathomimetic effects acting via adrenoceptors (?1, ?2,?1, ?2, ?3) or dopamine receptors (D1, D2).

May cause reflex bradycardia, reduce cardiac output and increase myocardial oxygen consumption

The respiratory quotient is the ratio of CO2 produced to O2 consumed while food is being metabolized:

RQ = CO2 eliminated/O2 consumed

Most energy sources are food containing carbon, hydrogen and oxygen. Examples include fat, carbohydrates, protein, and ethanol. The normal range of respiratory coefficients for organisms in metabolic balance usually ranges from 1.0-0.7.

Granulated sugar is a refined carbohydrate with no significant fat, protein or ethanol content.

The RQ for carbohydrates is = 1.0

The RQ for the rest of the compounds are:

Fats RQ = 0.7
The chemical composition of fats differs from that of carbohydrates in that fats contain considerably fewer oxygen atoms in proportion to atoms of carbon and hydrogen.

Protein RQ = 0.8
Due to the complexity of various ways in which different amino acids can be metabolized, no single RQ can be assigned to the oxidation of protein in the diet; however, 0.8 is a frequently utilized estimate.

Noradrenaline also called norepinephrine belongs to the catecholamine family that functions in the brain and body as both a hormone and neurotransmitter.

They have sympathomimetic effects acting via adrenoceptors (?1, ?2,?1, ?2, ?3) or dopamine receptors (D1, D2).

May cause reflex bradycardia, reduce cardiac output and increase myocardial oxygen consumption

Chest compressions are an essential part of cardiopulmonary resuscitation (CPR) which helps restore spontaneous circulation (ROSC).

Sodium bicarbonate is only prescribed in patients with cardiac arrests as a result of an overdose of tricyclic antidepressants or hyperkalaemia. Its use causes the body to produce more CO2 which causes:

Exacerbation of intracellular acidosis
Negative inotropy to ischaemic myocardium
Increased osmotic load of sodium into failing brain and body
Shift of oxygen dissociation curve to the left.

THAM is often used to treat metabolic acidosis as a result of cardiac bypass surgery and also cardiac arrest, when other standard methods have failed.

Carbicarb (Na2CO3 0.33 molar NaHCO3 0.33 molar) has only mild effects on acidosis. It also causes an increase in arterial CO2 pressure and lactate concentration.

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

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

There are different classes of electrical equipment that can be classified in the table below:

Class 1 – provides basic protection only. It must be connected to earth and insulated from the mains supply

Class II – provides double insulation for all equipment. It does not require an earth.

Class III – uses safety extra low voltage (SELV) which does not exceed 24 V AC. There is no risk of gross electrocution but risk of microshock exists.

Type B – All of above with low leakage currents (0.5mA for Class IB, 0.1 mA for Class IIB)

Type BF – Same as with other equipment but has ‘floating circuit’ which means that the equipment applied to patient is isolated from all its other parts.

Type CF – Class I or II equipment with ‘floating circuits’ that is considered to be safe for direct connection with the heart. There are extremely low leakage currents (0.05mA for Class I CF and 0.01mA for Class II CF)

Atrial natriuretic peptide (ANP) is secreted mainly from myocytes of right atrium and ventricle in response to increased blood volume.
It is secreted by both the right and left atria (right >> left).

It is a 28 amino acid peptide hormone, which acts via cGMP
degraded by endopeptidases.

It serves to promote the excretion of sodium, lowers blood pressure, and antagonise the actions of angiotensin II and aldosterone.

The standard error of the mean (SEM) is a measure of the spread expected for the mean of the observations – i.e. how ‘accurate’ the calculated sample mean is from the true population mean. The relationship between the standard error of the mean and the standard deviation is such that, for a given sample size, the standard error of the mean equals the standard deviation divided by the square root of the sample size.

SEM = SD / square root (n)

where SD = standard deviation and n = sample size

Glucose transport is a highly regulated process accomplished mostly by facilitated diffusion using carrier proteins to cross cell membranes.

There are many transporters, but the most important are known as glucose transporters (GLUTs).

Stresses in various form of acute and chronic forms affect the activity of glucose transporters.
They are responsive to many types of metabolic stress, including hypoxia, injury, hypoglycaemia, numerous metabolic inhibitors, stress hormones, and other influences such as growth factors.

Numerous signalling pathways appear to be involved in transporter regulation.

New evidence suggests that stresses regulating GLUTs are not only acute biological stresses. In addition, chronic low-grade inflammation, and their associated chronic diseases also lead to altered glucose transport. These include obesity, type 2 diabetes, cardiovascular disease, and the growth and spread of many tumours that are affected by altered glucose transporters. Some of these glucose transport effects are compensatory, while others are pathogenic.

Ultimately, deliberate manipulation of GLUTs could be used as treatment for some of these chronic diseases.

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).

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.

The diaphragm has three opening through which different structures pass from the thoracic cavity to the abdominal cavity:

Inferior vena cava passes at the level of T8.

Oesophagus, oesophageal vessels and vagi at T10.

Aorta, thoracic duct and azygous vein through T12.

Sympathetic trunk and pulmonary branches of vagus nerve form a posterior pulmonary plexus at the root of the lung. Fibres continue posteriorly from superficial cardiac plexus to form Anterior pulmonary plexus. It contains vagi nerves and superficial cardiac plexus. These fibres then follow the blood vessel and bronchi into the lungs.

The lower border of the pleura is at the level of:

8th rib in the midclavicular line

10th rib in the lower level of midaxillary line

T12 at its termination.

Both lungs have oblique fissure while right lung has transverse fissure too.

The trachea expands from the lower edge of the cricoid cartilage (at the level of the 6th cervical vertebra) to the carina.

Alpha 1 adrenergic receptor stimulation results in vasoconstriction of peripheral arteries mainly of those of skin, gut and kidney arterioles. This would cause and increase in total peripheral resistance and mean arterial pressure and as a result the perfusion of vital organs i.e. brain, heart and lungs are maintained.

Muscarinic M2 receptor also known as cholinergic receptor are located in heart, where they act to slow the heart rate down to normal sinus rhythm after negative stimulatory actions of parasympathetic nervous system. They also reduce contractile forces of the atrial cardiac muscle, and reduce conduction velocity of AV node. This could worsen the compensation.

Stimulation of beta 2 adrenergic receptor result in dilation of smooth muscle as in bronchodilation.

Beta 3 adrenergic receptors are present on cell surface f both white and brown adipocytes and are responsible for lipolysis, thermogenesis, and relaxation of intestinal smooth muscle.

Alpha 2 adrenergic receptor stimulation results in inhibition of the release of noradrenaline in a form of negative feedback.

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 attributable risk is the rate of a disease in an exposed group to that of a group that has not been exposed to it. It involves the measure of association that is pertinent to making decisions for the individuals.

Smallest drops reach not only the upper but also the lower respiratory tracks. As a result, the ultrasonic nebulizer is most efficient for the therapy of pulmonary diseases and stands out as a robust and reliable support within the clinical setting.

The correct answer is the mean, median and mode of normally distributed data are the same value. This is as a result of the bell shaped curve which is equal on both sides.

The bell-shape indicates that values around the mean are more frequent in occurrence than the values farther away.

In a normal distribution:
1) +/- one standard deviation of the mean accounts for 68% of the data.
2) +/- two standard deviations of the mean accounts for 95% of the data.
3) +/- three standard deviations of the mean accounts for 99.7% of the data.

The external iliac artery is the larger of the two branches of the common iliac artery. It forms the main blood supply to the lower limbs. The common iliac bifurcates into the internal and external iliac artery anterior to the sacroiliac joint.

The external iliac artery courses on the medial border of the psoas major muscles and exits the pelvic girdle posterior to the inguinal ligament. Here, midway between the anterior superior iliac spine and the pubic symphysis, the external iliac artery becomes the femoral artery and descends along the anteromedial part of the thigh in the femoral triangle.

The pectineus forms the posterior border of the femoral canal.
The femoral vein forms the lateral border of the femoral canal.
The medial border of the adductor longus muscle forms the medial wall of the femoral triangle.
The medial border of the sartorius muscle forms the lateral wall of the femoral triangle.

Prednisolone 5 mg is the same as 20 mg hydrocortisone.

Prednisolone 40 mg is the same as 8 x 20 mg or 160 mg of prednisolone.

Mineralocorticoid effects and variations in action duration are not taken into account in these comparisons.

5 mg of prednisolone is the same as Dexamethasone 750 mcg, Hydrocortisone 20 mg, Methylprednisolone 4 mg, and Cortisone acetate 25 mg.

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

9 & 27 can be obtained by subtracting and adding 9 from the mean. 9 is three times the standard deviation and we know that 99.7% values lie within 3 standard deviations from the mean. We can find the interval for 99.7% to verify in the following way:

For 99.7% confidence interval, you can find the range as follows:

1. Multiply the standard error by 3.

2. Subtract the answer from mean value to get the lower limit.

3. Add the answer obtained in step 1 from the mean value to get the upper limit.

4. The range turns out to be 9-27 kg.

The external urethral sphincter functions to provide voluntary control of urine flow from the bladder to the urethra.

It receives its innervation from the branches of the pudendal nerve which originate from S2, S3 and S4.

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.

The posterior inferior cerebellar artery is the largest branch arising from the distal portion of the vertebral artery which forms the basilar artery. It is one of the arteries responsible for providing blood supply to the brain’s cerebellum.

The labyrinthine artery (auditory artery) is a long and slender artery which arises from the basilar artery and runs alongside the facial and vestibulocochlear nerves into the internal auditory meatus.

The posterior cerebellar artery is one of two cerebral arteries supplying the occipital lobe with oxygenated blood. It is usually bigger than the superior cerebellar artery. It is separated from the vessel near its origin by the oculomotor nerve.

Soda-lime contains mostly calcium hydroxide (about 94%) and remaining sodium hydroxide.

CO2 + Ca(OH)2 → CaCO3 + H2O + heat
Here in this exothermic reaction, we can see that the production of calcium carbonate does not require heat.

When soda lime is allowed to dry with subsequent use of desflurane, isoflurane, and enflurane, it can lead to the generation of carbon monoxide.

Silica hardens the granules and can thus prevent disintegration.

The size of soda-lime granules is 4-8 mesh because it allows sufficient surface area for chemical reaction to occur without critically increasing the resistance to airflow.

Number needed to treat can be defined as the number of patients who need to be treated to prevent one additional bad outcome.

It can be found as:

NNT=1/Absolute Risk Reduction (rounded to the next integer since number of patients can be integer only).

where ARR= (Risk factor associated with the new drug group) — (Risk factor associated with the currently available drug)

So,

ARR= (0.04-0.03)

ARR= 0.01

NNT= 1/0.01

NNT=100

The heart has two venous drainage systems:
1. Greater venous system – it parallels the coronary arterial circulation and provides 70% venous drainage to the heart
2. Lesser venous system – includes the thebasian veins and provides up to 30% of the venous drainage to the heart

Thebasian veins (also called venae cordis minimae) are the smallest coronary veins and run in the myocardial layer of the heart. They serve to drain the myocardium and are present in all four heart chambers. They are more abundant on the right side of the heart and, more specifically, are most abundant in the right atrium. Thebesian veins drain the subendocardial myocardium either directly, via connecting intramural arteries and veins, or indirectly, via subendocardial sinusoidal spaces.

To begin, one must determine the child’s approximate weight. There are a variety of formulas to choose from. It is acceptable to use the advanced paediatric life support formula:

(age + 4) 2 = weight

A 5-year-old child will weigh around 18 kilogrammes.

The following are the appropriate doses of the drugs listed above:

Gentamicin (once daily) – 5-7 mg/kg = 90-126 mg and subsequent dose modified according to plasma levels
Ondansetron – 0.1 mg/kg, but a maximum of 4 mg as a single dose = 1.8 mg
Codeine should be administered orally at a dose of 1 mg/kg rather than intravenously, as the latter can cause ‘dangerous’ hypotension due to histamine release.
15 mg/kg paracetamol = 270 mg orally or intravenously (a loading dose of 20 mg/kg, or 360 mg, is sometimes recommended, which is not far short of the doses listed above).
Cefuroxime – the initial intravenous dose is 20 mg/kg (360 mg) depending on the indication (again, similar to the dose given in the answer options above).

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.

Selection bias is when randomisation is not achieved and is often a result of in efficient recruiting method.

Recall bias is specifically appropriate to the case control studies that is when ever the memories retrieved by the participants differ in accuracy.

Measurement bias can be characterized by gathering of information in a manner that is distorted.

When the participants of a research study are recruited from the hospitals rather than the general population, its called Berkson Bias.

Confounding bias is the major player here because in this case the effects of smoking can be masked behind and can be read as outcomes of lower socio economic status. This extraneous factor (Smoking), distorts the founding.

Cell membrane pore formation, Bacterial DNA damage, Peptidoglycan cross-linking inhibition, and peptidoglycan synthesis inhibitor are always lethal and such mechanisms are possible only in bactericidal drugs. But Protein synthesis inhibition would only prevent cell replication or cell growth and is responsible for bacteriostatic effects of the drug.

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.

The patient in the case has a fluid volume requirement of 30 mL/kg/day. His basic electrolyte requirement per day is:

Sodium at 2 mmol/kg/day x 110 = 220 mmol/day
Potassium at 1 mmol/kg/day x 110 = 110 mmol/day

His energy requirement per day is:

35 kcal/kg/day x 110 kg = 3850 kcal/day

One gram of glucose in fluid can provide approximately 4 kilocalories.

The following are the electrolyte components of the different intravenous fluids:

Fluid Na (mmol/L) K (mmol/L)
0.9% Normal saline (NSS) 154 0
0.45% NSS + 5% dextrose 77 0
0.18% NSS + 4% dextrose 30 0
Hartmann’s 131 5
5% dextrose 0 0

1000 mL of 5% dextrose has 50 g of glucose

Option B is inadequate for his sodium and caloric requirements (30 mmol of Na+ and 560 kcal). It is adequate for his K+ requirement (120 mmol of K+).

Option C is in excess of his Na+ requirement (462 mmol of Na+). Moreover, it does not provide any K+ replacement.

Option D is inadequate for his caloric requirement (600 kcal) and K+ requirement (60 mmol of K+). Moreover it does not provide any Na+ replacement.

Option E is in excess of his Na+ requirement (393 mmol of Na+), and is inadequate for his potassium requirement (15 mmol of K+)

Option A has adequate amounts for his Na+ (231 mmol of Na+) and K+ (120 mmol of K+) requirements. It is inadequate for his caloric requirement (600 kcal).

T cells function as a part of the body’s adaptive immune system. There are different types of T cells, including:

Cytotoxic T cells: Function as killer cells by releasing cytotoxic granules into the membrane of targeted cells.

T-Helper cells: When activated, they function to activate other immune cell types, assist in antibody production with B cells and releasing cytokines including IL-2.

Memory T cells: Function as to provide immune memory against already encountered antigens.

T cells possess specific glycoproteins and receptors on their surface.

T-Helper cells work with HLA class II antigens on the cell surfaces in order to recognise foreign antigens

T cells survive ranges from a few weeks, to a lifetime depending on the subtype in question.

Immunoglobulins are expressed on the surface of, and secreted by B-lymphocytes.

Native antigens are recognised by B cells. T cells only recognise antigens that have been processed by the cells and presented on the surface of the cell.

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..

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.

Chi-square test is used to determine the statistically significant different between categorical variables. It also determines the difference between expected frequencies and the observed frequencies.

Mann Whitney U test is used to determine the statistically significant different between two independent groups.

Wilcoxon’s test is the test of dependency. it determines the statistically significant difference between two dependent groups.

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.

ANOVA (analysis of variance) is similar to student’s t-test.

ANOVA is a statistical method used to determines the statistically significant difference between the mean of more than two group. In this experiment as we are dealing with three different group, ANOVA is most suitable test to determine the difference between each groups.

Lorazepam is an intermediate-acting benzodiazepine that binds to the GABA-A receptor subunit to increase the frequency of chloride channel opening and cause membrane hyperpolarization.

Lorazepam has emerged as the preferred benzodiazepine for acute management of status epilepticus. Lorazepam differs from diazepam in two important respects. It is less lipid-soluble than diazepam, with a distribution half-life of two to three hours versus 15 minutes for diazepam. Therefore, it should have a longer duration of clinical effect. Lorazepam also binds the GABAergic receptor more tightly than diazepam, resulting in a longer duration of action. The anticonvulsant effects of lorazepam last six to 12 hours, and the typical dose ranges from 4 to 8 mg. This agent also has a broad spectrum of efficacy, terminating seizures in 75-80% of cases. Its adverse effects are identical to those of diazepam. Thus, lorazepam also is an effective choice for acute seizure management, with the added possibility of a longer duration of action than diazepam.

Phenobarbitone is a long-acting barbiturate that binds to GABA-A receptor site and increase the duration of chloride channel opening. It also blocks glutamic acid neurotransmission, and, at high doses, can block sodium channels. It is considered as the drug of choice for seizures in infants.

Phenytoin is an anti-seizure drug that blocks voltage-gated sodium channels. It is preferred in prolonged therapy of status epilepticus because it is less sedating.

In cases wherein airway protection is required, thiopentone and propofol are the preferred drugs.

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

Insulin is the primary anabolic hormone that dominates regulation of metabolism during digestive phase. It promotes glucose uptake in skeletal myocytes and adipocytes, and other insulin-target cells. It promotes glycogenesis and inhibits gluconeogenesis.

Glucagon is the primary counterregulatory hormone that increases blood glucose levels, primarily through its effects on liver glucose output.

Similar to glucagon, growth hormone, catecholamines and corticosteroids are also counterregulatory factors released in response to decreased glucose concentrations. Growth hormone promotes glycogenolysis and inhibits gluconeogenesis; catecholamines stimulate glycogenolysis and gluconeogenesis; while corticosteroids stimulate glycogenesis and gluconeogenesis.

The laryngeal folds are comprised of two types of folds; the vestibular fold and the vocal fold. The vocal folds are mobile, and concerned with voice production. They are formed by the mucous membrane covering the vocal ligament. They are avascular, hence, are white in colour.

The internal branch of the superior laryngeal nerve provides sensation above the vocal cords. Lesions to this nerve may lead to loss of sensation above the vocal cords and loss of taste on the epiglottis.

The recurrent laryngeal nerve supplies the lateral and posterior cricoarytenoid, the thyroarytenoid. It also provides sensation below the vocal cords. Lesions to this nerve may cause respiratory obstruction, hoarseness, inability to speak and loss of sensation below the vocal cords.

The external branch of the superior laryngeal nerve supplies the cricothyroid muscle.

The glossopharyngeal nerve contains both sensory and motor components, and provides somatic innervation to the stylopharyngeus muscle, visceral motor innervation to the parotid gland, and carries afferent sensory fibres from the posterior third of the tongue, pharynx and tympanic cavity.

It is well known that atropine will cross the placenta and that maternal administration results in an increase in fetal heart rate.

Atropine is highly selective for muscarinic receptors. Its potency at nicotinic receptors is much lower, and actions at non-muscarinic receptors are generally undetectable clinically. Atropine does not distinguish among the M1, M2, and M3 subgroups of muscarinic receptors. In contrast, other antimuscarinic drugs are moderately selective for one or another of these subgroups. Most synthetic antimuscarinic drugs are considerably less selective than atropine in interactions with nonmuscarinic receptors.

A study on glycopyrrolate, a quaternary ammonium salt, was found to have a fetal: maternal serum concentration ratio of 0.4 indicating partial transfer.

Heparin, suxamethonium, and vecuronium do not cross the placenta.

Specific knowledge of the anatomical relationship is required to address this examination question.

The first rib is small and thick and contains a single facet that articulates at the costovertebral joint. It consist of a head, neck and shaft but a discrete angle is deficit. Along the side the shaft is indented with a groove for the subclavian artery and the lower brachial plexus trunk. Front to the scalene tubercle is a space for the subclavian vein.

The first rib has the scalenus front muscle joined to the scalene tubercle, isolating the subclavian vein (anteriorly) from the subclavian artery (posteriorly). This anatomical relationship is of major significance with respect to subclavian vein cannulation.

The 1st rib has the following relationships:

superior: lower trunk of the brachial plexus, subclavian vessels, clavicle.

inferior: intercostal vessels and nerves

posterior and inferior: pleura

anterior: sympathetic trunk (over neck)

superior intercostal artery, ventral T1 nerve root

The following is the Advanced Trauma Life Support (ATLS) classification of haemorrhagic shock:

Class I haemorrhage:
It has blood loss up to 15%. There is very less tachycardia, and no changes in blood pressure, RR or pulse pressure. Usually, fluid replacement is not required.

Class II haemorrhage:
It has 15-30% blood loss, equivalent to 750 – 1500 ml. There is tachycardia, tachypnoea and a decrease in pulse pressure. Patient may be frightened, hostile and anxious. It can be stabilised by crystalloid and blood transfusion.

Class III haemorrhage:
There is 30-40% blood loss. It portrays inadequate perfusion, marked tachycardia, tachypnoea, altered mental state and fall in systolic pressure. It requires blood transfusion.

Class IV haemorrhage:
There is > 40% blood volume loss. It is a preterminal event, and the patient will die in minutes. It portrays tachycardia, significant depression in systolic pressure and pulse pressure, altered mental state, and cold clammy skin. There is need for rapid transfusion and surgical intervention.

The vertebral (spinal) column is the skeletal central axis made up of approximately 33 bones called the vertebrae.

Cervical disc herniations occur when some or all of the nucleus pulposus extends through the annulus fibrosus. The most commonly affected discs are the C5-C6 and C6-C7 discs. Each vertebrae has a corresponding nerve root which arises at a level above it. This means that a hernation of the C5-C6 disc will cause a compression of the C6 nerve root.

The foramen transversarium is a part of the transverse process of each cervical vertebrae, however, the vertebral artery only runs through the C1-C6 foramen transversarium.

The costal facets are the point of joint formation between a rib and a vertebrae. As such, they are only present on the transverse processes of T1-T10.

The lumbar vertebrae do not form a joint with the ribs, nor do they possess a foramina in their transverse process.

Intervertebral discs are thickest in the cervical and lumbar regions of the spinal column. However, there are no discs between C1 and C2.

The first rib is an atypical rib. It is short, wide, and flattened and lies in an oblique plane.

It has a small scalene tubercle on its medial border which marks the point of attachment of scalenus anterior. The lower surface lies on the pleura and is smooth.

The tubercle on the upper surface separates an anterior groove for the subclavian vein and a posterior groove for the subclavian artery and lower trunk of the brachial plexus.

Scalenus medius is attached to a roughened area posterior to the groove for the subclavian artery.

The upper surface gives attachment anteriorly to the subclavius muscle and costoclavicular ligament.

Rifampicin is a derivative of a rifamycin (other derivatives are rifabutin and rifapentine). It is bactericidal against both dividing and non-dividing mycobacterium and acts by inhibiting DNA-dependent RNA polymerase. Thus this drug inhibits RNA synthesis.

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.

All of the muscles of the larynx are innervated by the recurrent laryngeal nerve, except the cricothyroid muscle.

Cricothyroid muscle is located deep in the anterior neck, between the cricoid and thyroid cartilage and is innervated by the external laryngeal nerve. Any injury to this muscle can cause paralysis and lead to hoarseness. When cricothyroid muscle contracts, it leads to tightening, stretching and thinning of the vocal folds. This produces higher-pitched sounds during vocalization.

A patient experiencing hoarseness due to possible injury to the external laryngeal nerve should be reassured that the hoarseness will resolve in time due to increased compensation from the other muscles.

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 correct answer is the clotting cascade, which occurs via a positive feedback mechanism. As clotting factors are attracted to a site, their presence attracts further clotting factors. This continues until a functioning clot is formed.

This patient has presented with symptoms of hypothyroidism and symptoms include weight gain, lethargy, cold intolerance, dry skin, coarse hair and constipation. It can be treated by replacing the missing thyroid hormone with levothyroxine which is a synthetic version of thyroxine (T4).

Serum carbon dioxide (CO2) is controlled via a negative feedback mechanism as well. Chemoreceptors can detect when the serum CO2 is high, and send an impulse to the respiratory centre of the brain to increase the respiratory rate. As a result, more CO2 is exhaled which lowers the serum concentration.

Cortisol is also released according to a negative feedback mechanism. Cortisol acts on both the hypothalamus and the anterior pituitary. Its action serve to decrease the formation of corticotrophin releasing hormone (CRH) and adrenocorticotropic hormone (ACTH), respectively. CRH acts on the anterior pituitary to release ACTH. This then acts on the adrenal gland to cause the release of cortisol. Thus, inhibition of CRH and ACTH formation results in high levels of cortisol which inhibit its further release.

Blood pressure (BP) is controlled via a negative feedback mechanism. Low BP results in renin-angiotensin-aldosterone system (RAAS) activation. This leads to vasoconstriction and retention of salt and water which increased BP.
Blood sugar is controlled via a negative feedback mechanism. A rise in blood sugar causes insulin to be released. Insulin acts to transport glucose into the cell which lowers blood sugar.

Tests are used to confirm the presence of a particular disease. However the results can be misleading at times since most of the tests have some limitations associated with them.
Sensitivity is the correct term that refers to the probability of a positive test. The others are explained below:

False Positive rates refer to the proportion of the patients who don’t have the condition being detected as positive.

False Negative rates refer to the proportion of the patients who have the condition being detected as negative (like the 20% of the patients that went undetected by the Ca-125 test).

Specificity describes the ability of a test to detect and pick up people without the disease. Absolute risk ratio compares the rate of two separate outcomes.

The intercostal nerves arise from the ventral rami of the first 11 thoracic spinal nerves. they course along the costal groove on the lower margin of the rib.

The twelfth intercoastal nerve is called the subcostal nerve. This is because it is below the 12th rib.

Each intercostal nerve is connected to a ganglion of the sympathetic trunk from which it carries preganglionic and postganglionic fibres that innervate blood vessels, sweat glands, and muscles.

The lateral and medial pectoral nerves innervates pectoralis major muscle.

Absolute risk reduction = (Control event rate) – (Experimental event rate)

Experimental event rate = 24 / 120 = 0.2

Control event rate = 60 / 240 = 0.25

Absolute risk reduction = 0.25 – 0.2 = 0.05 = 5% reduction

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%

Ondansetron is a serotonin antagonist at the 5HT3 receptor. 5HT3 receptors in the gastrointestinal tract and in the vomiting centre of the medulla participate in the vomiting reflex. They are particularly important in vomiting caused by chemical triggers such as cancer chemotherapy drugs.

The nucleus solitarius is the recipient of all visceral afferents, and an essential part of the regulatory centres of the internal homeostasis, through its multiple projections with cardiorespiratory and gastrointestinal regulatory centres. It participates in the reflexes of the nerves innervating the nucleus, so it mediates cough reflex, carotid sinus reflex, gag reflex, and vomiting reflex.

Hypochondriasis is an illness anxiety disorder, and describes excessively worriedness about the presence of a disease. While the woman is concerned about her possibility of developing motor neurone disease, she understands that no symptoms have yet appeared. Hypochondriasis involves patients who refuse to accept that they don’t have the disease, even if the results come back negative.

Late Look Bias occurs when the data is gathered or analysed at an inappropriate time e.g. when many of the subjects suffering from a fatal disease have died. This type of biasness might occur in some retrospective studies of motor neurone disease, but is not applicable to this prospective study.

In procedure bias, the researcher decides assignment of a treatment versus control and assigns particular patients to one group or the other non-randomly. This is unlikely to have occurred in this case, although it is not mentioned specifically. Of all the options, lead time-bias is a better answer.

The Hawthorne Effect refers to groups modifying their behaviour simply because they are aware of being observed. Any differences in the behaviour have not been mentioned in the question, and it is highly unlikely that a change in patient’s behaviour would have affected their length of survival in this case.

The correct option is lead-time bias. Even if the new blood test diagnoses the disease earlier, it doesn’t affect the outcome, as the survival time was still on average 43 months from the onset of symptoms in both groups. With the help of blood test, the disease was only detected 8 months earlier.

The correct answer is the Purkinje fibres, which conducts at a velocity of about 4m/sec.

The electrical conduction system of the heart starts with the SA node which generates spontaneous action potentials.

This is conducted across both atria by cell to cell conduction, and occurs at around 1 m/s. The only pathway for the action potential to enter the ventricles is through the AV node in a normal heart.
At this site, conduction is very slow at 0.05ms, which allows for the atria to completely contract and fill the ventricles with blood before the ventricles depolarise and contract.

The action potentials are conducted through the Bundle of His from the AV node which then splits into the left and right bundle branches. This conduction is very fast, (,2m/s), and brings the action potential to the Purkinje fibres.

Purkinje fibres are specialised conducting cells which allow for a faster conduction speed of the action potential (,2-4m/s). This allows for a strong synchronized contraction from the ventricle and thus efficient generation of pressure in systole.

Vecuronium is used as a part of general anaesthesia to provide skeletal muscle relaxation during surgery or mechanical ventilation. It is a monoquaternary aminosteroid (not quaternary) non- depolarising neuromuscular blocking drug.

It has a structure similar to both rocuronium and pancuronium. The only difference is the substitution of specific groups on the steroid structure.

Vecuronium is not associated with the release of norepinephrine from sympathetic nerve endings. However, Pancuronium has norepinephrine releasing the property.

Among the types of muscles, cardiac muscles have the greatest number if mitochondria due to the heart energy requirements.

Approximately 35% of the cardiac muscle volume is due to the mitochondria. While in skeletal and smooth muscles, it comprises 3-8% of the muscle volume.

Type I muscle fibre has a slow contraction velocity, with a red fibre colour, and predominantly uses oxidative phosphorylation to produce a sustained contraction. It contains more mitochondria and myoglobin than type II, and is often used for endurance training.

Type II muscle fibre has a fast contraction velocity, a white fibre colour, and predominantly uses anaerobic glycolysis. It has fewer mitochondria and myoglobin, and is often used for weight or resistance training and sprinting.

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.

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.

Glycolysis occurs in the cytoplasm of the cell. It converts 1 glucose molecule (6-carbon) to pyruvate (two 3-carbon molecules) and produces 4 ATP molecules and 2NADH but uses 2 ATP in the process with an overall net energy production of 2 ATP.

Pyruvate is then oxidised to acetyl coenzyme A (generating 2 NADH per pyruvate molecule). This takes place in the mitochondria and then enters the Krebs cycle (citric acid cycle). It produces 2 ATP, 8 NADH and 2 FADH2 per glucose molecule.

Electron transport phosphorylation takes place in the mitochondria. The aim of this process is to break down NADH and FADH2 and also to pump H+ into the outer compartment of the mitochondria. It produces 32 ATP with an overall net production of 36ATP.

In anaerobic respiration which occurs in the cytoplasm, pyruvate is reduced to NAD producing 2 ATP.

Staphylococcus aureus infection is the most likely cause.

Surgical site infections (SSI) occur when there is a breach in tissue surfaces and allow normal commensals and other pathogens to initiate infection. They are a major cause of morbidity and mortality.

SSI comprise up to 20% of healthcare associated infections and approximately 5% of patients undergoing surgery will develop an SSI as a result.
The organisms are usually derived from the patient’s own body.

Measures that may increase the risk of SSI include:
-Shaving the wound using a single use electrical razor with a disposable head
-Using a non iodine impregnated surgical drape if one is needed
-Tissue hypoxia
-Delayed prophylactic antibiotics administration in tourniquet surgery, patients with a prosthesis or valve, in clean-contaminated surgery of in contaminated surgery.

Measures that may decrease the risk of SSI include:
1. Intraoperatively
– Prepare the skin with alcoholic chlorhexidine (Lowest incidence of SSI)
-Cover surgical site with dressing

In contrast to previous individual RCT’s, a recent meta analysis has confirmed that administration of supplementary oxygen does not reduce the risk of wound infection and wound edge protectors do not appear to confer benefit.

2. Post operatively
Tissue viability advice for management of surgical wounds healing by secondary intention

Use of diathermy for skin incisions
In the NICE guidelines the use of diathermy for skin incisions is not advocated. Several randomised controlled trials have been undertaken and demonstrated no increase in risk of SSI when diathermy is used.

Resistance pulmonary arteries constrict in response to alveolar and airway hypoxia, diverting blood to better-oxygenated alveoli.

In atelectasis, pneumonia, asthma, and adult respiratory distress syndrome, hypoxic pulmonary vasoconstriction optimises O2 uptake. Hypoxic pulmonary vasoconstriction helps maintain systemic oxygenation during single-lung anaesthesia.

A redox-based O2 sensor within pulmonary artery smooth muscle cells is involved in hypoxic pulmonary vasoconstriction. The production of reactive oxygen species by smooth muscle cells in the pulmonary artery varies in proportion to PaO2. Hypoxic removal of these redox second messengers inhibits voltage-gated potassium channels, depolarizing smooth muscle cells in the pulmonary artery.

L-type calcium channels are activated by depolarization, which raises cytosolic calcium and causes hypoxic pulmonary vasoconstriction. Some anaesthetics suppress this response, increasing the risk of further deterioration in ventilation perfusion mismatch.

Agents that inhibit HPV are ether, halothane, and desflurane (>1.6 MAC).
Agents with no effect on HPV include thiopentone, fentanyl, desflurane (1MAC), isoflurane (<1.5MAC), sevoflurane(1MAC), and propofol.

A ‘double blind crossover study’ happens when every patient receive both treatments.

It is incorrect to say that only half of the patients do not know which treatment they receive because in a double blind placebo control clinical trial ALL of the patients are blind to their treatment choice .

If some of the patients are not treated, they would be aware that they were not being treated and it could not be considered a blind trial.

In a double blind placebo control clinical trial both the clinician and the patient are blind to the treatment choice. The clinician assessing the effects of the treatment, therefore, does not know which treatment the patient has been given.

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

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.

During normal tissue metabolism, there is production of CO2 (acid) which is then expired by the lungs. If metabolism switches from aerobic to anaerobic due to a lack of oxygen, the tissues are unable to completely oxidise sugars to CO2. As a consequence, the sugars can only be partially oxidised to lactic acid. Since lactic acid cannot be expired by the lungs, it remains in the circulation leading to metabolic acidosis.

Also, normal tissue metabolism leads to the production of some amount of acid from the breakdown of proteins. These acids are excreted from the body by kidney filtration. Renal failure will therefore results in acidosis after several days.

An increased acidosis stimulates the brain’s respiratory centres to increase the respiratory rate. This lowers the CO2 in the blood, leading to a decrease in its acidity. Renal excretion removes the excess acid, resulting in a normal pH, and a reduced PaCO2 and HCO3.

pH PaCO2 (kPa) HCO3
Compensated respiratory acidosis 7.34 7.2 29
Acute respiratory acidosis 7.25 7.3 22
Compensated metabolic acidosis 7.34 3.6 14
Metabolic acidosis 7.21 5.3 15
Metabolic alkalosis 7.51 5.1 30

Ptosis and mydriasis are visible in surgical third nerve palsy, and the eye looks ‘down and out.’ The loss of innervation to all of the major structures supplied by the oculomotor nerve is reflected in these characteristics.

Ptosis is caused by the paralysis of the levator palpebrae superioris in oculomotor nerve palsy. Due to the unopposed actions of the superior oblique and lateral rectus muscles, the eye rotates down and out.

Mydriasis is caused by surgical (compressive) causes of third nerve palsy, which disrupt the parasympathetic pupillomotor fibres on the nerve’s periphery.

Medical (ischaemic) causes of a third nerve palsy, on the other hand, leave the superficial parasympathetic fibres relatively unaffected and the pupil unaffected.

Horner’s syndrome is characterised by ptosis, anhidrosis, and miosis, which are caused by a loss of sympathetic innervation to the tarsal muscle of the upper lid, facial skin, and dilator pupillae, respectively.

Moderately high doses of dopamine produce a positive inotropic (direct?1 and D1 action + that due to Noradrenaline 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.

The degree of correlation is summarised by the correlation coefficient (r). This indicates how closely the points lie to a line drawn through the plotted data. In parametric data this is called Pearson’s correlation coefficient and can take any value between -1 to +1. A correlation of -1.0 indicates a perfect negative correlation, and a correlation of 1.0 indicates a perfect positive correlation.

For example

r = 1 – strong positive correlation (e.g. systolic blood pressure always increases with age)

r = 0 – no correlation (e.g. there is no correlation between systolic blood pressure and age)

r = – 1 – strong negative correlation (e.g. systolic blood pressure always decreases with age)

Whilst correlation coefficients give information about how one variable may increase or decrease as another variable increases they do not give information about how much the variable will change. They also do not provide information on cause and effect.

In contrast to the correlation coefficient, linear regression may be used to predict how much one variable changes when a second variable is changed.

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

T12 – Coeliac trunk

L1 – Left renal artery

L2 – Testicular or ovarian arteries

L3 – Inferior mesenteric artery

L4 – Bifurcation of the abdominal aorta

Severity of a reduction in restrictive defect (%FVC) or obstructive defect (%FEV1/FVC) predicted are classified as follows:

Mild 70-80%
Moderate 60-69%
Moderately severe 50-59%
Severe 35-49%
Very severe <35% This patient has a mixed deficit with a severe obstructive deficit as %FEV1/FVC predicted is 46.9% and a moderate restrictive deficit as %FVC of predicted is 61.3 FEV1/FVC ratio 80% < predicted and VC < 80% = mixed picture. FEV1/FVC ratio 80% < predicted and VC > 80% = obstructive picture.

FEV1/FVC ratio 80% > predicted and VC > 80% = normal picture.

FEV1/FVC ratio 80% > predicted and VC < 80% predicted= restrictive picture.

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.

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

The superficial inguinal ring is an opening in the aponeurosis of the external oblique muscle, just above and lateral to the pubic crest.

The superficial ring resembles a triangle more than a ring with the base lying on the pubic crest and its apex pointing towards the anterior superior iliac spine. The sides of the triangle are crura of the opening in the external oblique aponeurosis. The lateral crura of the triangle is attached to the pubic tubercle. The medial crura of the triangle is attached to the pubic crest.

The external oblique aponeurosis forms the anterior wall of the inguinal canal and also the lateral edge of the superficial inguinal ring. The rectus abdominis lies posteromedially, and the transversalis posterior to this.

The liver receives blood supply from two sources.
1. Hepatic artery proper
It arises from the celiac trunk via the common hepatic artery and brings oxygenated blood to the liver.
It contributes to approximately 30% of the blood supply of the liver.
2. Hepatic portal vein – supplies the liver with partially deoxygenated blood, carrying nutrients absorbed from the small intestine. It gets tributaries from the inferior mesenteric vein, splenic vein, and superior mesenteric vein

The inferior mesenteric artery supplies the hindgut.
The superior mesenteric artery supplies the pancreas and intestine up to the proximal two-thirds of the transverse colon.
The inferior phrenic artery supplies the inferior surface of the diaphragm and oesophagus.

Medical gas cylinders are made up of molybdenum steel but not cast iron. They are checked and assessed at a regular interval.

At least one cylinder in each hundred are tested for tensile, pressure, smash, twist and straightening.

Nitrous Oxide cylinders contain a mixture of liquid and vapour at a pressure of approx. 4500 kPa or 45 Bar. Carbon dioxide cylinder contain gas at the pressure of 5000kPa.

The filling ratio is the ratio of mass of liquified gas in the cylinder to the mass of water required to fill the cylinder at the temperature of 15ºC. In the united kingdom, filling ratio of liquid nitrous oxide is 0.75. The cylinders are usually attached to the anaesthetic machine. As nitrous oxide is an N-methyl-d-aspartate receptor antagonist that may reduce the incidence of chronic post-surgical pain.

Metabolic equivalent (MET) measures the energy expenditure of an individual.

It is calculated mathematically by:

MET = (VO2 max/weight)/3.5 = 21/3.5 = 6 METs

Where 1 MET = 3.5 mL O2/kg/minute is utilized by the body.

Note:

1 MET Eating
Dressing
Use toilet
Walking slowly on level ground at 2-3 mph
2 METs Playing a musical instrument
Walking indoors around house
Light housework
4 METs Climbing a flight of stairs
Walking up hill
Running a short distance
Heavy housework, scrubbing floors, moving heavy furniture
Walking on level ground at 4 mph
Recreational activity, e.g. golf, bowling, dancing, tennis
6 METs Leisurely swimming
Leisurely cycling along the flat (8-10 mph)
8 METs Cycling along the flat (10-14 mph)
Basketball game
10 METs Moderate to hard swimming
Competitive football
Fast cycling (14-16 mph)

Breathing system is an assembly of components which connects patient’s airway to anaesthesia machine through which controlled composition of gas mixture is dispensed. It delivers gas to the patient, removes expired gas and controls the temperature and humidity of the inspired mixture. It allows spontaneous, controlled, or assisted respiration. It may also provide ports for gas sampling, airway pressure, flow and volume monitoring.

Breathing systems have been classified by Conway and Mapleson.
Conway suggested a functional classification:
– Circuits requiring a CO2 absorber
– Circuits not requiring a CO2 absorber

William Mapleson designated varying arrangements of breathing system components (masks, breathing tubes, fresh gas flow inlets, adjustable pressure-limiting valves, and reservoir bags) as Mapleson A-E circuits.
Mapleson A: Arranged as FGF inlet, reservoir bag, APL valve, mask.
In this circuit, because the reservoir bag is between the FGF inlet valve and the APL valve, expired gas from the patient may re-enter the system and fill the reservoir bag during controlled ventilation. This is the most efficient system for spontaneous breathing as the FGF must only be equal to a patient’s minute ventilation to prevent rebreathing.

Mapleson B: Arranged as reservoir bag, FGF inlet, APL valve, mask.
In this circuit, the FGF inlet is closer to the APL valve, which helps prevent the rebreathing concern in the Mapleson A circuit as above during controlled ventilation.

Mapleson C: Arranged as reservoir bag, FGF inlet, APL valve, mask.
In this circuit, the arrangement is the same as the Mapleson B circuit. However, this circuit is shorter as it does not contain elongated corrugated tubing. This circuit also has the FGF inlet close to the APL valve to aid in preventing rebreathing.

Mapleson D: Arranged as reservoir bag, APL valve, FGF inlet, and mask.
In this circuit, the arrangement interchanges the FGF inlet and APL valve of the Mapleson A circuit. This system prevents rebreathing by directing FGF towards the APL valve rather than towards the patient during exhalation.

Mapleson E: Arranged as corrugated tubing, FGF inlet, and mask.
In this circuit, there is no reservoir bag and no APL valve. Given the inability to alter the pressure of the circuit, this is ideal for spontaneously ventilating neonates or paediatric patients where low-pressure ventilation is desired. The system prevents rebreathing, similar to the Mapleson D circuit.

Jackson Rees later modified the Mapleson E by adding an open ended bag, which has since become known as the Mapleson F.
Mapleson F: Arranged as APL valve directly connected to reservoir bag, corrugated tubing, FGF inlet, and mask.
The system prevents rebreathing similarly to Mapleson D by directing FGF towards the APL valve.

The patellar (knee jerk) reflex is a monosynaptic stretch reflex arising from L2-L4 nerve roots. It occurs after a tap on the patellar tendon which causes the spindles of the quadriceps muscles to stretch.

The afferent nerve pathway occurred through A gamma fibres.

Wesphal’s sign refers to a reduction, or absence of the patellar reflex. It is often indicated of a neurological disease affecting the PNS.

A transection of the spinal cord results in a degree of shock which causes all reflexes to be reduced or completely absent, and required a period of approximately 6 weeks to recover.

Decreased platelet concentrations with eclampsia were described as early as 1922 by Stancke. The platelet count is routinely measured in women with any form of gestational hypertension. The frequency and intensity of thrombocytopenia vary and are dependent on the severity and duration of the preeclampsia syndrome and the frequency with which platelet counts are performed.

Overt thrombocytopenia defined by a platelet count < 100,000/microliter - indicates severe disease. In general, the lower the platelet count, the higher the rates of maternal and fetal morbidity and mortality. In most cases, delivery is advisable because thrombocytopenia usually continues to worsen. After delivery, the platelet count may continue to decline for the first day or so. It then usually increases progressively to reach a normal level within 3-5 days. In some instances with HELLP syndrome, the platelet count continues to fall after delivery. If these do not reach a nadir until 48 to 72 hours, then preeclampsia syndrome may be incorrectly attributed to one of the thrombotic microangiopathies. The following are other severe features associated with preeclampsia: Proteinuria: >/= 300 mg/24 hours; or urine protein: creatinine ratio >/= 0.3; or dipstick 1+

Renal insufficiency: serum creatinine > 1.1 mg/dL or doubling of creatinine in the absence of other renal disease

Impaired liver function: two times elevated AST/ALT or unexplained right upper quadrant pain or epigastric pain unresponsive to medications

Pulmonary oedema

Cerebral or visual symptoms: headache, visual disturbances

The tibial nerve lies on top of the vessels contained within the inferior aspect of the popliteal fossa.

In the superior aspect of the fossa, the tibial nerve runs lateral to the vessels, before then travelling superficial to the vessels, and then finally changing course to lie medial to the vessels.

The popliteal artery is the most deep structure present in the popliteal fossa

Atrial natriuretic peptide (ANP) is secreted mainly from myocytes of right atrium and ventricle in response to increased blood volume.
It is secreted by both the right and left atria (right >> left).

It is a 28 amino acid peptide hormone, which acts via cGMP
degraded by endopeptidases.

It serves to promote the excretion of sodium, lowers blood pressure, and antagonise the actions of angiotensin II and aldosterone.

Approximately 25% of phase-1 drug reactions is made responsible by CYP2D6.

As much as a 1,000-fold difference in the ability to metabolise drugs by CYP2D6 can happen between phenotypes, and this may result in adverse drug reactions (ADRs).

The metabolism of antiemetics, beta-blockers, codeine, tramadol, oxycodone, hydrocodone, tamoxifen, antidepressants, neuroleptics, and antiarrhythmics is also as a result of CYP2D6.

Patients who take drugs that are metabolised by CYP2D6 but have poor CYP2D6 metabolism are more likely to have ADRs. People with ultra-rapid CYP2D6 metabolism may have a decreased drug effect due to low plasma concentrations of these drugs.

All the other CYP enzymes are subject to genetic polymorphism. Variants are less likely to lead to adverse drug reactions.

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.

An intra-operative air embolism occurs when air becomes trapped in the blood vessels during surgery.

A transoesophageal echocardiography (OE) uses invasive echocardiography to monitor the integrity and performance of the heart. It is the gold standard as it provides real-time imaging of the heart to enable early diagnosis and treatment.

Precordial doppler ultrasonography can also be used to detect into-operative air emboli. It is non-invasive and more practical, but is less sensitive.

A change in end-tidal CO2 could be indicative of and increase in physiological dead-space, but could also be indicative of any processes that reduces the excretion or increases the production of CO2, making it non-specific.

A transoesophageal stethoscope can be used to listen for the classic mill-wheel murmur produced by a large air embolus.

The inferior vena cava is formed by the union of the right and left common iliac veins. This occurs at the L5 vertebral level. The IVC courses along the right anterolateral side of the vertebral column and ascends through the central tendon of the diaphragm at the T8 vertebral level.

Pupil size is reduced by the pupillary light reflex and during accommodation for near vision. In the pupillary light reflex, light that strikes the retina is processed by retinal circuits that excite W-type retinal ganglion cells. These cells respond to diffuse illumination. The axons of some of the W-type cells project through the optic nerve and tract to the pretectal area, where they synapse in the olivary pretectal nucleus. This nucleus contains neurons that also respond to diffuse illumination. Activity of neurons of the olivary pretectal nucleus causes pupillary constriction by means of bilateral connections with parasympathetic preganglionic neurons in the Edinger-Westphal nuclei. The reflex results in contraction of the pupillary sphincter muscles in both eyes, even when light is shone into only one eye.

ARR= (Risk factor associated with the new drug group) — (Risk factor associated with the currently available drug)

So,

ARR= (24/120)-(60/240)

ARR= 0.2-0.25

ARR= 0.05 (Numerical Value)

ARR= 5%

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.

Electromagnetic waves are categorized according to their frequency or equivalently according to their wavelength. Visible light makes up a small part of the full electromagnetic spectrum.

Electromagnetic waves with shorter wavelengths and higher frequencies include ultraviolet light, X-rays, and gamma rays. Electromagnetic waves with longer wavelengths and lower frequencies include infrared light, microwaves, and radio and televisions waves.

Different electromagnetic waves according to their wavelength from shorter to longer are X-rays, ultraviolet radiations, visible light, infrared radiation, radio waves. X-ray among electromagnetic waves has the shortest wavelength and higher frequency with wavelengths ranging from 10*-8 to 10* -12 and corresponding frequencies.

Iron is a necessary micronutrient for proper erythropoietic function, oxidative metabolism, and cellular immune responses. Although dietary iron absorption (1-2 mg/d) is tightly controlled, it is only just balanced by losses.

The adult body contains 35-45 mg/kg iron (about 4-5 g)

Iron can be found in a variety of forms, including haemoglobin, ferritin, haemosiderin, myoglobin, haem enzymes, and transferrin bound proteins.

The needle should be inserted just below the skin at the mid inguinal point which is the surface indicator for the femoral artery.

Also known as the “product limit estimate’’, the Kaplan-Meier survival plot is used to estimate the true survival function from the collected data.

Using this plot, probabilities of occurrence of an event at a certain point in time can be computed. The successive probabilities are multiplied by any earlier computed probabilities to get the final estimate. For a given population, the survival probability at any particular time on the plot = (number of subjects living at the start – number of subjects who died)/number of subjects living at the start.

The description of a scatter plot is a graphical representation using Cartesian coordinates to display values for more than two variables for data set. It is used for to assess the relationship between 2 different variables.

Sixty-seven percent of filtered water is reabsorbed in the proximal tubule. The driving force for water reabsorption is a transtubular osmotic gradient established by reabsorption of solutes (e.g., NaCl, Na+-glucose).

Henle’s loop reabsorbs approximately 25% of filtered NaCl and 15% of filtered water. The thin ascending limb reabsorbs NaCl by a passive mechanism, and is impermeable to water. Reabsorption of water, but not NaCl, in the descending thin limb increases the concentration of NaCl in the tubule fluid entering the ascending thin limb. As the NaCl-rich fluid moves toward the cortex, NaCl diffuses out of the tubule lumen across the ascending thin limb and into the medullary interstitial fluid, down a concentration gradient as directed from the tubule fluid to the interstitium. This mechanism is known as the counter current multiplier.

The distal tubule and collecting duct reabsorb approximately 8% of filtered NaCl, secrete variable amounts of K+ and H+, and reabsorb a variable amount of water (approximately 8%-17%).

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.

The spinal cord and the vertebral canal are as long as each other in early fetal life. The length of the cord increases faster than the growth of the vertebrae during development. By the time of birth, the spinal cord is at the level of the lower border of the 3rd lumbar vertebra, compared to its original position at the level of the 2nd coccygeal vertebra.

Among the breathing circuits, the Lack circuit is the most efficient for spontaneous breathing.

An outer coaxial tube is present to deliver fresh air; exhaust air is routed to an inner tube, which is then delivered to a scavenging system. An expiratory valve is seen at the patient end, which is an advantage over other circuits. Moreover, the Lack circuit prevents rebreathing slightly greater than the alveolar minute ventilation at 4-5 litres per minute.

The Bain circuit prevents rebreathing at 160-200ml/kg per minute, and is a co-axial version of the Mapleson D circuit.

The Mapleson E circuit prevent rebreathing at a fresh gas flow (FGF) of approximately twice the patient’s normal minute volume. A modification of this, the Mapleson F, has a reservoir bag at the opposite end for the FGF. This circuit is appropriate for paediatric patients with a body weight less than 20 kg.

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 ideal gas equation makes the following assumptions:

The gas particles have a small volume in comparison to the volume occupied by the gas.
Between the gas particles, there are no forces of interaction.
Individual gas particle collisions, as well as gas particle collisions with container walls, are elastic, meaning momentum is conserved.
PV = nRT
Where:

P = pressure
V = volume
n = moles of gas
T = temperature
R = universal gas constant

Helium is a monoatomic gas with a small helium atom. The attractive forces between helium atoms are small because the helium atom is spherical and has no dipole moment. Because helium atoms are spherical, collisions between them approach the ideal state of elasticity.

Most real gases behave qualitatively like ideal gases at standard temperatures and pressures. When intermolecular forces and molecular size become important, the ideal gas model tends to fail at lower temperatures or higher pressures. It also fails to work with the majority of heavy gases.

Helium, argon, neon, and xenon are noble or inert gases that behave the most like an ideal gas. Xenon is a noble gas with a much larger atomic size than helium.

The dose-response curve plots the graph of the dose (drug concentration) versus the response. As doses increase, the response increment diminishes; finally, doses may be reached at which no further increase in response can be achieved. This relation between drug concentration and effect is traditionally described by a hyperbolic curve. When the x-axis is plotted in log scale, the graph yields a sigmoid curve.

Efficacy (Emax) and potency (EC50) can be derived from this curve. Emax is the maximal effect achievable, with increasing concentration of a drug. EC50 is the concentration of the drug, wherein half of the maximal effect is achieved.

When the graph is plotted using a log [response/1-response] against log dose, the sigmoid curve becomes a straight line (Hill plot). A graph that transforms from a straight line to exponential curve is mathematically incorrect. A graph that transforms from either a wash-in or wash-out exponential curve to a straight line comes from an initial set of data plotted against time, to a logarithmic transformation of the initial data set against time.

This question is asking which structure would lie posterior to the rectus abdominis muscle and not the prosthetic mesh, as only peritoneum lies posterior to mesh during a total extraperitoneal (TEP) hernia repair.

The region of the repair lies below the arcuate line, meaning that the transversalis fascia and peritoneum lie posterior to the rectus abdominis.

The bucks fascia lies within the penis.

Superior vena cava is the main vein bringing blood back to the heart. It can get partially or completely blocked by various causes, the most common being due to malignant tumours of the mediastinum.

There are collateral pathways that form in long-standing cases with 60% or more stenosis and continue venous drainage in cases of superior vena obstruction. The collaterals are classified into four as follows:

1. The azygos-hemiazygos pathway
Azygos, hemiazygos, intercostal, and lumbar veins.

2. The internal and external mammary pathway
internal mammary, superior epigastric, and inferior epigastric veins and superficial veins of the thorax.

3. The lateral thoracic pathway
Lateral thoracic, thoracoepigastric, superficial circumflex, long saphenous, and femoral veins to collateralize to the IVC.

4. The vertebral pathway
Innominate, vertebral, intercostal, lumbar, and sacral veins to collateralize to the azygos and internal mammary pathways.

Because the patient has mild systemic disease, he is ASA 2 and the procedure will be performed under local anaesthesia.

The following factors should be considered when requesting preoperative investigations:

Indications derived from a preliminary clinical examination
Whether or not a general anaesthetic will be used, the possibility of asymptomatic abnormalities, and the scope of the surgery.

No special investigations are needed if the patient has no history of significant systemic disease and no abnormal findings on examination during the nurse-led assessment.

The measurements of GFR are done using renally inert indicators like inulin, where passive rate of filtration at the glomerulus = rate of excretion. Normal value is about 180 litres per day.

GFR is altered by renal blood flow but blood flow does not need to be measured.

The reabsorption of Na leads to a low excretion rate and low urine concentration and therefore its use as an indicator would lead to an erroneously LOW GFR.

If there is tubular secretion of any solute, the clearance value will be higher than that of inulin. This will be either due to tubular reabsorption or the solute not being freely filtered at the glomerulus.

Standard error can be calculated by the following formula:

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

The anterior cerebral artery supplies the midline portion of the frontal lobe and the superior medial parietal lobe of the brain. It also supplies the front four-fifths of the corpus callosum and provides blood to deep structures such as the anterior limb of the internal capsule, part of the caudate nucleus, and the anterior part of the globus pallidus.

The cerebral hemispheres are supplied by arteries that make up the Circle of Willis. The Circle of Willis is formed by the anastomosis of the two internal carotid arteries and two vertebral arteries.

Clinically, the internal carotid arteries and their branches are often referred to as the anterior circulation of the brain. The anterior cerebral arteries are connected by the anterior communicating artery. Near their termination, the internal carotid arteries are joined to the posterior cerebral arteries by the posterior communicating arteries, completing the cerebral arterial circle around the interpeduncular fossa, the deep depression on the inferior surface of the midbrain between the cerebral peduncles.

The middle cerebral artery supplies part of the frontal, temporal and parietal lobes.

The posterior cerebral artery supplies the occipital lobe.

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.

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 basal metabolic rate (BMR) is the amount of energy required to maintain basic bodily functions in the resting state. The unit is Watt (Joule/second) or calories per unit time.

Indirect calorimetry measures O2 consumption and CO2 production where gases are collected in a canopy which is the gold standard, Douglas bag, face-mask dilution technique or interfaced with a ventilator.

The BMR can be calculated using the Weir formula:

Metabolic rate (kcal per day) = 1.44 (3.94 VO2 + 1.11 VCO2)

The BMR should be measured while lying down and at rest with the following conditions met:

It should follow a 12 -hour fast
No stimulants ingested within a 12-hour period
It should be done in a neutral thermal environment (between 20°C-25°C)

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.

The shaft of the humerus has two prominent features:
1. Deltoid tuberosity – attachment for the deltoid muscle
2. Radial or spiral groove – The radial nerve and profunda brachii artery lie in the groove

Mid-shaft fractures of the humerus usually occur after a direct blow to the upper arm, which can occur after a fall or RTAs. The most important clinical significance of a mid-shaft humeral fracture is an injury to the radial nerve. The radial nerve originates from the brachial plexus and has roots of C5-T1. It crosses the spiral groove on the posterior side of the shaft of the humerus.
On examination, the patient may have a wrist drop, loss or weakness of finger extension, and decreased or absent sensation to the posterior forearm, digits 1 to 3, and the radial half of the fourth digit.

The following parts of the humerus are in direct contact with the indicated
nerves:
Surgical neck: axillary nerve.
Radial groove: radial nerve.
Distal end of humerus: median nerve.
Medial epicondyle: ulnar nerve.

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%.

Bilirubin is formed by metabolizing heme, mostly from haemoglobin in red blood cells.

Bilirubin is conjugated to glucuronic acid in the hepatocytes by the glucuronyl transferase enzyme in order to enable it to become soluble and allow for its secretion across the canalicular membrane and into bile.

The conjugation process is increased by rifampicin and decreased by valproate.

Gilbert’s syndrome is caused by a decrease in glucuronyl transferase in the hepatic system, decreasing the transport of bilirubin into the hepatocyte, causing unconjugated bilirubinaemia.

Crigler-Najjer syndrome is caused by mutations in the genes responsible for hepatic glucuronyl transferase, decreasing the activity of the enzyme, meaning bilirubin cannot be conjugated, causing unconjugated bilirubinaemia.

Dubin-Johnson syndrome does not cause an impairment in the conjugation of bilirubin, but it blocks the transport of bilirubin out of the hepatocyte resulting in conjugated bilirubinaemia.

To begin, one must determine the child’s approximate weight. There are a variety of formulas to choose from. It is acceptable to use the advanced paediatric life support formula:

(Age + 4) 2 = Weight

A 5-year-old child will weigh around 18 kilogrammes.

10 mcg/kg (0.1 ml/kg of 1 in 10 000 adrenaline) = 180 mcg is the appropriate dose of intravenous or intraosseous adrenaline.

The correct energy level to deliver is 4 J/kg, which equals 72 joules.

The pad size that is appropriate for this patient is 8-12 cm. For an infant, a 4.5 cm pad is appropriate.

To allow adequate separation in infants and small children, the pads should be placed anteriorly and posteriorly on the chest.

When using a bag and mask to ventilate, take two breaths for every 15 chest compressions. If chest compressions are being applied intubated and without interruption, a ventilation rate of 10-20 breaths per minute should be given.

Chest compressions should be done at a rate of 100-120 per minute, the same as an adult.

Phase I and phase II metabolism are used by the liver to break down paracetamol.

1st Phase:

Prostaglandin synthetase and cytochrome P450 (CYP1A2, CYP2E2, CYP3A4 and CYP2D6) to N-acetyl-p-benzoquinoneimine (NAPQI) and N-acetylbenzo-semiquinoneimine. NAPQI is a toxic metabolite that binds to the sulfhydryl groups of cellular proteins in hepatocytes, making it toxic. This can result in centrilobular necrosis.

Glutathione and glutathione transferases prevent NAPQI from binding to hepatocytes at low paracetamol doses by preferentially binding to these toxic metabolites. The cysteine and mercapturic acid conjugates are then excreted in the urine. Depletion of glutathione occurs at higher doses of paracetamol, resulting in high levels of NAPQI and the risk of hepatocellular damage. Hepatotoxicity would not be an issue if the body’s glutathione stores were sufficient.

N-acetylcysteine is a precursor for glutathione synthesis and is the drug of choice for the treatment of paracetamol overdose.

Phase II:

Conjugation with glucuronic acid to paracetamol glucuronide is the most common method of metabolism and excretion, accounting for 60% of renally excreted metabolites. Paracetamol sulphate (35%), unchanged paracetamol (5%), and mercapturic acid are among the other renally excreted metabolites (3 percent ). The capacity of conjugation pathways is limited. The capacity of the sulphate conjugation pathway is lower than that of the glucuronidation pathway.

Because of the low pH in the stomach, paracetamol absorption is minimal (pKa value is 9.5). Paracetamol is absorbed quickly and completely in the alkaline environment of the small intestine. Oral bioavailability is extremely high, approaching 100%.

As a result, measuring paracetamol levels in plasma after an injury is important. Peak plasma concentrations are reached after 30-60 minutes, with a volume of distribution of 0.95 L/kg. It binds to plasma proteins at a rate of 10% to 25%.

The normal peak inspiratory flow in healthy individuals is 20-30 L/min during each normal tidal ventilation. This is expected to increase with greater respiratory rate and deeper inspiration.

Face masks are used to facilitate the delivery of oxygen from a breathing system to a patient. Face masks can be divided into two types: fixed performance or variable performance devices.

In fixed performance devices (also known as high air flow oxygen enrichment or HAFOE), fixed inspired oxygen concentration is delivered to the patent, independent and greater than that of the patient’s peak inspiratory flow rate (PIFR). No random entrainment is expected to occur at the time of PIFR, hence, the oxygen concentration in HAFOE devices is not dependent on the patient’s respiratory pattern.

Moreover, in HAFOE masks, the concentration of oxygen at a given oxygen flow rate is determined by the size of the constriction; a device with a greater entrainment aperture delivers a lower oxygen concentration. Therefore, a 40% Venturi device will have lesser entrainment aperture when compared to a 31% Venturi. Venturi masks allow relatively fixed concentrations of supplemental oxygen to be inspired e.g. 24%, 28%, 31%, 35%, 40% and 60% oxygen. These are colour coded and marked with the recommended oxygen flow rate.

Variable performance devices deliver variable inspired oxygen concentration to the patient, and is dependent on the PIFR. The PIFR can often exceed the flow rate at which oxygen or an oxygen/air mixture is supplied by the device, depending on a patient’s inspiratory effort. In addition, these masks allow expired air to be released through the holes in the sides of the mask. Thus, with increased respiratory rate, rebreathing of alveolar gas from inside the mask may occur.

Crystalloids recommended for fluid resuscitation include 0.9% N saline and Hartmann’s solution(a physiological solution). 0.9% N. saline is not a physiological solution for the following reasons:

Compared with the normal range of 98-102 mmol/L, its chloride concentration is high (154 mmol/L)
It lacks calcium, magnesium, glucose and potassium
It does not have bicarbonate or bicarbonate precursor buffer necessary to maintain plasma pH within normal limits

There is a difference in the activity (concentration) of strong ions at a physiological pH. This imbalance can explain abnormalities of acid base balance. A normal strong ion difference (SID) is in the order of 40.

SID = ([Na+] + [K+] + [Ca2+] + [Mg2+]) – ([Cl-] + [lactate] + [SO42-])

This imbalance is made up with the weaker anions to maintain electrical neutrality.
Administration of a large volume of 0.9% normal saline during resuscitation results in excessive chloride administration and this impairs renal bicarbonate reabsorption. The SID of 0.9% normal saline is 0 (Na+ = 154mmol/L and Cl- = 154mmol/L = 154 – 154 = 0). A large volume of NS will decrease the plasma SID causing an acidosis.

Other causes of a hyperchloremic acidosis are:

Diabetic ketoacidosis
Total Parenteral Nutrition
Overdose of ammonium chloride and hydrochloric acid
Gastrointestinal losses of bicarbonate like in diarrhoea and pancreatic fistula
Proximal renal tubular acidosis with failure of bicarbonate reabsorption

A thermocouple, or a thermal junction, is temperature measuring device consisting of a pair of dissimilar metal (bimetallic) wires or strips joined together. Typically, copper and constantan (an alloy of 55% copper and 45% nickel) are used. When there is contact between these metals, a small voltage is generated in the order of millivolts. The magnitude of the thermojunction electromotive force (emf) is proportional to applied temperature (the Seebeck effect). This physical principle is applied in the measurement of temperature. The electromotive force at the measuring junction is proportional to temperature.

Two wires with different coefficients of expansion, joined together, can be used as a switch for thermostatic control.

Semiconductors are NOT used in thermocouple. The resistance of the measuring junction of a thermocouple is irrelevant.

A significant early feature of the metabolic response to trauma and surgery is hyperglycaemia. It is due to an increased glucose production and decreased glucose utilisation bought on by neuroendocrine stimulation. Catecholamines, Growth hormone, ACTH and cortisol, and Glucagon are all increased.

There is also a decreased insulin sensitivity peripherally and an inhibition of insulin production from the beta cells of the pancreas. These changes lead to hyperglycaemia.

The stress response to endoscopic surgery will only be prevented with use of high dose opioids or central neuraxial block at anaesthesia.
To reduce the risk of inducing hyperchloremic acidosis, Ringer’s lactate/acetate or Hartmann’s solution is preferred to 0.9% sodium chloride as routine maintenance fluids.

Though it has been suggested that administration of Hartmann’s solution to patients with type 2 diabetes leads to hyperglycaemia, one Litre of Hartmann’s solution would yield a maximum of 14.5 mmol of glucose. A rapid infusion of this volume would increase the plasma glucose by no more than 1 mmol/L..

Dexamethasone, a glucocorticoid, produces hyperglycaemia by stimulating gluconeogenesis . Glucocorticoids are agonists of intracellular glucocorticoid receptors. Their effects are mainly mediated via altered protein synthesis via gene transcription and so the onset of action is slow. The onset of action of dexamethasone is about one to four hours and therefore would NOT contribute to the hyperglycaemia in this patient in the time given.

0.9% Normal saline with or without adrenaline is the usual irrigation fluid. With this type of surgery, systemic absorption is unlikely to occur.

Fentanyl is not likely the primary cause of hyperglycaemia in this patient. In high doses (50 mcg/Kg) it has been shown to reduce the hyperglycaemic responses to surgery.

The neuroleptic malignant syndrome 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 ICU care, anticholinergic drugs, increasing dopaminergic activity with Amantadine, L-dopa, and dantrolene, and non- depolarising neuromuscular blockade drugs

T3 is produced by peripheral de-iodination of T4. It is more active than T4.

TBG, like most binding proteins, is increased in pregnancy. Because of this, measurement of free thyroid hormone concentration is more important than total.

T4 and T3 concentrations are decreased in Illness and starvation.

L-T4 that is the active molecule while D-T4 is inactive.

Coronary perfusion pressure(CPP), the difference between aortic diastolic pressure (Pdiastolic) and the left ventricular end-diastolic pressure (LVEDP), is mainly determined by the formula:

CPP = Pdiastolic -LVEDP
where
Pdiastolic is the lowest pressure in the aorta before left ventricular ejection and
LVEDP is measured directly during a cardiac catheterisation or indirectly using a pulmonary artery catheter. The pulmonary artery occlusion or wedge pressure approximates best with LVEDP.

Using this patient’s haemodynamic data:

CPP = Pdiastolic – MPAWP
COO = 70 – 12 = 58mmHg

Propofol is considered a safe drug to use in porphyria because even if causes mild elevation of porphyrins inpatient, it does not cause any symptoms.

Since barbiturates are inducers of ALA synthetase, they are contraindicated in porphyria patients. So, thiopentone most not be used.

Etomidate is a potent inhibitor of adrenal 11 beta-hydroxylase and 17 alpha-hydroxylase reducing cortisol and aldosterone synthesis in the adrenal cortex and has been associated with exacerbations of porphyria in animal studies and it is advisable not to use it in this condition.

Ketamine should be reserved for the hemodynamically unstable patient, however, it is a safe drug.

Diazepam is safe in porphyria but is not usually used for a rapid sequence induction.

The subclavian artery lies behind and partly above the subclavian vein. 3-4% of the time, it can be inadvertently cannulated during cannulation of the subclavian vein

Because of its anatomical position, putting pressure on the subclavian artery is impossible so arresting bleeding with pressure when it is punctured is not viable.

One of the consequences of subclavian vein cannulation (1%) is pleural puncture leading to a pneumothorax. This is because the apical pleura is inferior and caudal to the subclavian vein.

Mast cell tryptase is a reliable marker of mast cell degranulation. Tryptase is a protease enzyme that acts via widespread protease-activated receptors (PARs).

Variance and standard deviation indicate the dispersion of the plot from mean value and thus are not really helpful in summarizing the mean.

Range is the difference between maximum and minimum value that is 45 in this case.

The mean in this case is 6.2 due to the presence of an outlier 45. In the presence of outlier mean can be misleading as it is quite sensitive to skewness in data.

Mode is the most frequent value. In this case mode has 4 values: 0,1,2,4.

In case of skewedness, median is the most apt representative of the mean as it is not affected by outliers. In this case since the data set has even values i.e. 10. Median is the average of the 5th & 6th entry after arranging the data in ascending order like that in case of the question (0,0,1,1,2,2,3,4,4,45). This turns out to be 2.

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 AAGBI and the British Hypertension Society has published guidelines for the measurement of adult blood pressure and management of hypertension before elective surgery.

The objective is to ensure that patients admitted for elective surgery have a known systolic blood pressure below 160 mmHg and diastolic blood pressures below 100 mmHg. The primary health care teams, if possible, should ensure that this is the case and provide evidence to the pre-assessment clinic staff or on admission.

Avoiding cancellation on the day of surgery because of white coat hypertension is a secondary objective.

Patients with blood pressures below 180 mmHg systolic and 110 mmHg diastolic (measured in the preop assessment clinic), who present to pre-operative assessment clinics without documented evidence of primary care blood pressures should proceed to elective surgery.

In this question, the history/assessment does not appear to point to obvious end-organ damage so there is no indication for further investigation for secondary causes of hypertension or an echocardiogram at this point. Further review and treatment at this point is not required.

However, you should write to the patient’s GP and encourage serial blood pressure measurements in the primary health care setting.