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)

When the eye is compressed or the extra-ocular muscles are tractioned, the oculocardiac reflex causes a decrease in heart rate.

The ophthalmic division of the trigeminal nerve provides the afferent limb. This synapses with the vagus nerve’s visceral motor nucleus in the brainstem. The efferent signal is carried by the vagus nerve to the heart, where increased parasympathetic tone reduces sinoatrial node output and slows heart rate.

The most common symptom is sinus bradycardia, but junctional rhythm and asystole can also occur.

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

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

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

The Marsh model describes a propofol TCI model for adults

The Minto model applies to TCI remifentanil.

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

The option that is most responsible is the progressive decrease in venous return of blood to the right atrium. The heart rate does not usually change with PEEP so the fall in cardiac output is due to a reduction in left ventricular (LV) stroke volume (SV).

Note that the interventricular septum does shift toward the left and there is an increased pulmonary vascular resistance (PVR) from overdistention of alveolar air sacs that contribute to the reduction in cardiac output. Any increase in PVR will be associated with reduced pulmonary vascular capacitance.

The Delphi technique was developed in the 1950s and is a widely used and accepted method for achieving convergence of opinion concerning real-world knowledge solicited from experts within certain topic areas. Choosing the appropriate subjects is the most important step in the entire process because it directly relates to the quality of the results generated, despite this, there is no exact criterion currently listed in the literature concerning the selection of Delphi participants.

Therefore, due to the potential scarcity of qualified participants and the relatively small number of subjects used in a Delphi study, the ability to achieve and maintain an ideal response rate can either ensure or jeopardize the validity of a Delphi study.

Oxytocin is structurally similar to Antidiuretic Hormone (ADH) and thus oxytocin cause water intoxication (due to ADH like action)

Oxytocin is secreted by the posterior pituitary along with ADH. It increases uterine contractions – the contraction of the upper segment (fundus and body) of the uterus whereas the lower segment is relaxed facilitating the expulsion of the foetus

Antidiuretic hormone (ADH) also called vasopressin is released from the posterior pituitary in response to hypertonicity and increases fluid reabsorption from the kidney.

Doxazosin is selective alpha 1 blocker (so causes less tachycardia than a nonselective alpha-blocker) and is the drug of choice for a patient with hypertension and benign hyperplasia of the prostate (BHP).

The major adverse effect of alpha-blocker is first-dose hypotension.

Loop diuretics act by causing inhibition of Na+ K+ 2Cl– symporter present at the luminal membrane of the ascending limb of the loop of Henle.

Furosemide, torsemide, bumetanide, ethacrynic acid, furosemide, piretanide, tripamide, and mersalyl are the important members of this group

The main use of loop diuretics is to remove the oedema fluid in renal, hepatic, or cardiac diseases. Thus they are useful in the treatment of acute heart failure. These can be administered i.v. for prompt relief of acute pulmonary oedema (due to vasodilatory action).

Hypokalaemia, hypomagnesemia, hyponatremia, alkalosis, hyperglycaemia, hyperuricemia, and dyslipidaemia are seen with both thiazides as well as loop diuretics

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

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

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

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

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

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

Phosphate is the principal anion of the intracellular fluid, most of which is bound to either lipids or proteins. They dissociate or associate with different compounds, depending on the enzymatic reaction, thus forming a constantly shifting pool.

Calcium and magnesium are also present intracellularly, however in lesser amounts than phosphate.

Sodium is the most abundant extracellular cation, and Chloride and is the most abundant extracellular anion.

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.

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.

The measure of drug potency or therapeutic response is the ED95. This is defined as the dose of a neuromuscular blocking drug required to produce a 95% depression of muscle twitch height. The ED50 and ED90 describe a depression of twitch height by 50% and 90% respectively.

The ED95 (mg/kg) of the commonly used neuromuscular blocking agents are:

suxamethonium: 0.27
rocuronium: 0.31
vecuronium: 0.04
pancuronium: 0.07
cisatracurium: 0.04
mivacurium: 0.08

Hydrochloric acid is lost when you vomit for a long time (HCl). As a result, the following can be expected, in varying degrees of severity:

Hypokalaemia
Hypochloraemia
Increased bicarbonate to compensate for chloride loss and metabolic alkalosis

The alkalosis causes potassium to move from the intracellular to the extracellular compartment at first. Long-term vomiting and dehydration cause potassium to be excreted by the kidneys in order to conserve sodium. Dehydration can cause urea and creatinine levels to rise.

The actual base excess is always greater than the standard base excess.

The actual base excess (BE) is a measurement of a base’s contribution to a blood gas picture’s metabolic component. It’s the amount of base that needs to be added to a blood sample to bring the pH back to 7.4 after the respiratory component of a blood gas picture has been corrected (PaCO2 of 40 mmHg or 5.3 kPa). The BE has a normal range of +2 to 2. A large positive BE indicates a severe metabolic alkalosis, while a large negative BE indicates a severe metabolic acidosis. As a result, the actual BE in vitro is unaffected by CO2.

In vivo, however, standard BE is not independent of pCO2 because blood with haemoglobin acts as a better buffer than total ECF.

As a result, it is impossible to tell the difference between compensating for a respiratory disorder and compensating for the presence of a primary metabolic disorder.

The differences between in vitro and in vivo behaviour can be mostly eliminated if the BE is calculated for a haemoglobin concentration of 50 g/L (the ‘effective’ or virtual value of Hb if it was distributed throughout the extracellular space) rather than the actual haemoglobin. Because haemoglobin has a lower buffering capacity, the standard BE is higher than the actual BE. It reflects the BE better in the extracellular space rather than just the intravascular compartment.

The external laryngeal nerve arises from the superior laryngeal nerve and provides innervation to the cricothyroid muscle.

The other muscles mentioned receive their innervations from the recurrent laryngeal nerve.

Sensory innervation of the larynx is controlled by branches of the vagus nerve.

The internal and external bifurcations of the superior laryngeal nerve is responsible for sensory innervation of the aspect of the larynx superior to the vocal cords, while the recurrent laryngeal nerve is responsible for sensory innervation of the intrinsic musculature of the larynx except for the cricothyroid muscle.

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.

Canon waves: which refer to large waves present on the trace that do not correspond to the A, V or C waves. They usually occur in a background of complete heart blocks or junctional arrythmias.

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

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

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

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

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

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

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

Cholera usually doesn’t cause bloody diarrhoea.

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

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

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

Capnography is the non-invasive measurement and pictorial display of inhaled and exhaled carbon dioxide (CO2) partial pressure.

It is depicted graphically as the concentration of CO2 over time.

It is used in disease diagnosis, determining disease severity, assessing response to treatment and is the best method to for indicating when an endotracheal tube is placed in the trachea after intubation.

The wavelength of IR light usually absorbed by nitrous oxide is between 4.4-4.6?m (very close to that of CO2). Its absorption of wavelengths at 3.9 ?m is much weaker. It causes a measurable deficit of 0.1% for every 10% of nitrous oxide. The maximal wavelength of infrared (IR) light absorbed by carbon monoxide is 4.7 ?m. The volatile agents have strong absorption bands at 3.3 ?m and throughout the ranges 8-12 ?m.

IR light is not absorbed by oxygen (O2), but O2 and CO2 molecules are constantly colliding which interrupts the absorption of IR light by CO2. This increases the band of absorption, that is the Collison or pressure broadening). An oxygen percentage of 95 will result in a 0.5 percentage fall in CO2 measure.

IR light is also absorbed by water vapour which will result in an overlap of the absorption band, collision broadening and a dilution of partial pressure. This is why water trap and water permeable tubing is recommended for use as it reduces measurement inaccuracies.

The use of multi-gas analysers of modern gases also help reduce the effects of collision broadening.

Beer’s law is also applied in this system as an increase in the concentrations of CO2 causes a decrease in the amount of IR able to pass through the gas. This IR light is what generated the signal that is analysed for display.

The capnograph can indicate oesophageal intubation, but cannot determine if it is endotracheal or endobronchial. For this, auscultation is used.

Sodium-chloride symporter inhibitor.

The thiazide sensitive sodium chloride symporter is inhibited by thiazides at the proximal portion of the distal convoluted tubule leading to increased sodium and water excretion. Increased delivery of sodium to the distal portion of the distal convoluted tubule promotes potassium loss. This is why thiazides are associated with hyponatraemia and hypokalaemia.

Carbonic anhydrase inhibitors are used mainly in the treatment of glaucoma. They act on the proximal convoluted tubule to promote bicarbonate, sodium and potassium loss.

Sodium potassium chloride symporter is inhibited by Loop diuretics.
Epithelial sodium channels are inhibited by Amiloride.
Drugs which lead to nephrogenic diabetes insipidus such as lithium and demeclocycline, are Inhibitors of vasopressin.

The study is being conducted on a smaller level with only 200 participants and is determining the effectiveness of the drug in comparison to a placebo. These characteristics are in accordance with the second phase of trial.

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 clinical signs suggest a class II haemorrhage – 15-30% of circulating blood volume has been lost.

Pelvic fractures are associated with significant concealed haemorrhage (>2000 ml) and may require aggressive fluid resuscitation. Other priorities include stabilisation of the fracture(s) and pain relief.

The Advanced Trauma Life Support (ATLS) classification of haemorrhagic shock is as follows:

Class I haemorrhage (blood loss up to 15%):
<750 ml of blood loss
Minimal tachycardia
No changes in blood pressure, RR or pulse pressure
Normally not require fluid replacement as will be restored in 24 hours, but in trauma correct.

Class II haemorrhage (15-30% blood volume loss):
Uncomplicated haemorrhage requiring crystalloid resuscitation
Represents about 750 – 1500 ml of blood loss
Tachycardia, tachypnoea and a decrease in pulse pressure (due to a rise in diastolic component due action of catecholamines)
Minimal systolic pressure changes
Anxiety, fright or hostility
Can usually be stabilised by crystalloid, but may later require a blood transfusion.

Class III haemorrhage (30-40% blood volume loss):
Complicated haemorrhagic state in which at least crystalloid and probably blood replacement are required
Classical signs of inadequate perfusion, marked tachycardia, tachypnoea, significant changes in mental state and measurable fall in systolic pressure
Almost always require blood transfusion, but decision based on patient initial response to fluid resuscitation.

Class IV haemorrhage (> 40% blood volume loss):
Preterminal event patient will die in minutes
Marked tachycardia, significant depression in systolic pressure and very narrow pulse pressure (or unobtainable diastolic pressure)
Mental state is markedly depressed
Skin cold and pale
Need rapid transfusion and immediate surgical intervention.

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

The route of choice is an arm vein (cephalic) with one or two large bore cannula. This will enable initial aggressive fluid resuscitation. A central line can be inserted at a later stage if central venous monitoring is deemed necessary. If a suitable peripheral vein cannot be cannulated with a large bore cannula then the internal jugular vein could be accessed rapidly (preferably ultrasound guided).

Intravenous access below the diaphragm in this case is inadvisable when other routes are available.

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

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

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

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

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.

Cardiac conduction

Phase 0 – Rapid depolarization. Opening of fast sodium channels with large influx of sodium

Phase 1 – Rapid partial depolarization. Opening of potassium channels and efflux of potassium ions. Sodium channels close and influx of sodium ions stop

Phase 2 – Plateau phase with large influx of calcium ions. Offsets action of potassium channels. The absolute refractory period

Phase 3 – Repolarization due to potassium efflux after calcium channels close. Relative refractory period

Phase 4 – Repolarization continues as sodium/potassium pump restores the ionic gradient by pumping out 3 sodium ions in exchange for 2 potassium ions coming into the cell. Relative refractory period

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

The following factors influence rate of diffusion across the placenta:

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

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

The cervical plexus is a complex network of nerves within the head and neck region, providing nerve innervation to regions within the head, neck and trunk.

It is comprised of nerves arising from the anterior primary rami of the C1-C4 nerve roots.

The cervical plexus gives off superficial and deep branches. The superficial branches penetrate through the deep fascia at the centre point of the posterior border of the sternocleidomastoid. It provides sensory innervation from the lower border of the mandible to the 2nd rib. The deep branches provide motor innervation to the neck and diaphragmatic muscles.

Cervical plexus block is surgically relevant as it is used to provide regional anaesthesia for procedures in the neck region. The anaesthesia should be injected into the centre point of the posterior border of the sternocleidomastoid. Complications arise when anaesthesia is instead injected into the wrong point, including into the vertebral artery, subarachnoid and epidural spaces, blockade of phrenic and recurrent laryngeal nerves, and the cervical sympathetic plexus.

Secreted T4 and T3 circulate in the bloodstream almost entirely bound to proteins. Normally only about 0.03% of total plasma T4 and 0.3% of total plasma T3 exist in the free state. Free T3 is biologically active and mediates the effects of thyroid hormone on peripheral tissues in addition to exerting negative feedback on the pituitary and hypothalamus. The major binding protein is thyroxine-binding globulin (TBG), which is synthesized in the liver and binds one molecule of T4 or T3. About 70% of circulating T4 and T3 is bound to TBGl 10% to 15% is bound to another specific thyroid-binding protein called transthyretin (TTR). Albumin binds 15% to 20%, and 3% to lipoproteins. Ordinarily only alterations in TBG concentration significantly affect total plasma T4 and T3 levels.

Two important biological functions have been ascribed to TBG. First, it maintains a large circulating reservoir of T4 that buffers any acute changes in thyroid gland function. Second, binding of plasma T4 and T3 to proteins prevents loss of these relatively small hormone molecules in urine and thereby helps conserve iodide. TTR transports T4 in CSF and provides thyroid hormones to the CNS.