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Question 1
Incorrect
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Which of the following correctly explains the mechanism of lowering blood pressure by nitroglycerine?
Your Answer: Nitric oxide
Correct Answer: Acetylcholine
Explanation:Nitroglycerine is rapidly denitrated enzymatically in the smooth muscle cell to release the free radical nitric oxide (NO).
Released NO activated cytosolic guanylyl cyclase which increases cGMP (cyclin guanosine monophosphate) which causes dephosphorylation of myosin light chain kinase (MLCK) through a cGMP-dependent protein kinase.
Reduced availability of phosphorylated (active) MLCK interferes with activation of myosin and in turn, it fails to interact with actin to cause contraction. Consequently, relaxation occurs. -
This question is part of the following fields:
- Pharmacology
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Question 2
Correct
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Given the following hormones, which of these will stimulate glycogenesis and gluconeogenesis?
Your Answer: Corticosteroids
Explanation: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.
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This question is part of the following fields:
- Pathophysiology
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Question 3
Incorrect
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The SI unit of measurement is kgm2s-2 in the System international d'unités (SI). Which of the following derived units of measurement has this format?
Your Answer: Power
Correct Answer: Energy
Explanation:The derived SI unit of force is Newton.
F = m·a (where a is acceleration)
F = 1 kg·m/s2The joule (J) is a converted unit of energy, work, or heat. When a force of one newton (N) is applied over a distance of one metre (Nm), the following amount of energy is expended:
J = 1 kg·m/s2·m =
J = 1 kg·m2/s2 or 1 kg·m2·s-2The unit of velocity is metres per second (m/s or ms-1).
The watt (W), or number of joules expended per second, is the SI unit of power:
J/s = kg·m2·s-2/s
J/s = kg·m2·s-3Pressure is measured in pascal (Pa) and is defined as force (N) per unit area (m2):
Pa = kg·m·s-2/m2
Pa = kg·m-1·s-2 -
This question is part of the following fields:
- Physiology
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Question 4
Correct
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A current flows through a simple electric circuit. Which of the following electrical component configurations has the greatest potential difference?
Your Answer: Two 5 ohm resistors in series with a passing current of 10 ampere
Explanation:According to the Ohm’s law, the potential difference is defined as
V(potential difference) = I(current) x (R) resistance
So, for one resistor of 5 ohms, a 10 ampere current will generate:
V = I x R
V = 10 x 5
V = 50 voltsThe formula for resistors in series can be defined as:
R(total) = R1+R2
Hence, when a current of 10 amperes passes through two 5 ohms resistors that are connected in series, the potential difference is:
V = I x (R1+R2)
V = 10 x (5+5)
V = 10 x 10
V = 100 voltsThe formula for resistors that are connected in a parallel circuit is:
1/ Rtotal = 1/R1 + 1/R2
Hence, when a current of 10 amperes passes through two 5 Ω resistors that are connected in a parallel circuit, the potential difference is:
Rtotal = R1 × R2/ R1 + R2
Rtotal = 25/10
Rtotal = 2.5
V = I x R
V = 10 x (R1xR2 / R1 + R2)
V = 10 x (25/10)
V = 10 x 2.5
V = 25 voltsCapacitors are electronic components that have the ability to store energy and charge (Q). The derived SI unit of capacitance (C) is the farad (F), which is equivalent to one coulomb per volt (V). The typical capacitors usually have a very small capacitance range, that ranges from pico to microfarads. On the contrary, supercapacitors can have a capacitance of up to 1-5000 F.
There are a number of factors that eventually determine the capacitance (C). They are as follows:
– Larger plate area (A)
– Closer plate spacing (d)
– Permittivity (ε) of the material (dielectric) between the plates (vacuum<<<glass), – C = ε × A/dThe units of stored charge are coulombs (Q), which is equal to the pathway of one ampere of current per second.
Stored charge, capacitance and voltage can be defined by the following equation:V (potential difference across capacitor) = Q(charge) / C (capacitance)
In a parallel circuit, the formula of capacitors is:
Ctotal = C1 + C2
Hence, two 5 farad capacitors in a parallel circuit arrangement with a charge of 100 coulomb and capacitance 10 F will give a potential difference of::
V = 100/10
V = 10 voltsIn a series circuit, the formula for capacitors is:
1/Ctotal = 1/C1 + 1/C2
Hence, two 5 farad capacitors with a charge of 100 coulomb will give:
Ctotal = C1 × C2/C1 + C2
In the example total capacitance = 25/10 = 2.5 F
V = 100/2.5
V = 40 volts. -
This question is part of the following fields:
- Anaesthesia Related Apparatus
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Question 5
Correct
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A 64-year old male has shortness of breath on exertion and presented to the cardiology clinic. He has a transthoracic echo performed to help in assessing the function of his heart. How can this echo aid in calculating cardiac output?
Your Answer: (end diastolic LV volume - end systolic LV volume) x heart rate
Explanation:Cardiac output = stroke volume x heart rate
Left ventricular ejection fraction = (stroke volume / end diastolic LV volume ) x 100%
Stroke volume = end diastolic LV volume – end systolic LV volume
Pulse pressure = Systolic Pressure – Diastolic Pressure
Systemic vascular resistance = mean arterial pressure / cardiac output
Factors that increase pulse pressure include:
-a less compliant aorta (this tends to occur with advancing age)
-increased stroke volume -
This question is part of the following fields:
- Physiology And Biochemistry
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Question 6
Correct
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An study on post-operative nausea and vomiting (PONV) among paediatric patients who underwent tonsillectomy showed a decrease in incidence from 10% to 5% following a new management protocol. Which of the following best estimates the numbers needed to treat (NNT) for one additional patient to benefit from the new management of PONV?
Your Answer: 20
Explanation:The Number Needed to Treat (NNT) is the number of patients you need to treat to prevent one additional bad outcome. For example, if a drug has an NNT of 5, it means you have to treat 5 people with the drug to prevent one additional bad outcome.
To calculate the NNT, you need to know the Absolute Risk Reduction (ARR); the NNT is the inverse of the ARR:
NNT = 1/ARR
Where ARR = CER (Control Event Rate) €“ EER (Experimental Event Rate).
NNTs are always rounded up to the nearest whole number.
In this case, the NNT can be computed as follows:
ARR = 10% – 5% = 0.05
NNT = 1/0.05 = 20
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This question is part of the following fields:
- Statistical Methods
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Question 7
Incorrect
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Bacteria and viruses that are smaller than 0.1 μm in diameter can be filtered out using heat and moisture exchanger (HME) with a typical pore size 0.2 μm. Choose the most appropriate mechanisms of particle capture for most bacteria and viruses.
Your Answer: Inertial impaction
Correct Answer: Diffusion
Explanation:Warming, humidifying, and filtering inspired anaesthetic gases is done by heat and moisture exchangers (HME) and breathing system filters. They are made of glass fibres materials and are supported by a sturdy frame. Pleating increases the surface area to reduce resistance to air flow and boost efficiency.
Filters’ effectiveness is determined by the amount and size of particles they keep out of the patient’s airway. The efficiency of filters might be classified as 95, 99.95, or 99.97 percent. Pores with a diameter of 0.2 µm are common. The following are examples of typical particle sizes:
Red blood cell – 5 µm
Lymphocyte – 5-8 µm
Viruses – 0.02-0.3 µm
Bacteria – 0.5-1 µm
Depending on particle size, gas flow speed, and charge, particles are collected via a number of processes. Mechanical sieve, interception, diffusion, electrostatic filtration, and inertial impaction are some of the options:Sieve:
The diameter of the particle the filter is supposed to collect is smaller than the apertures of the filter’s fibres.Interception:
When a particle following a gas streamline approaches a fibre within one radius of itself, it becomes attached and captured.
Diffusion:A particle’s random (Brownian) zig-zag path or motion causes it to collide with a fibre.
By attracting and capturing a particle from within the gas flow, it generates a lower-concentration patch within the gas flow into which another particle diffuses, only to be captured. At low gas velocities and with smaller particles (0.1µm diameter), this is more common.Electrostatic:
These filters use large diameter fibre media and rely on electrostatic charges to improve fine particle removal effectiveness.
Impaction due to inertia:
When a particle is too large to respond fast to abrupt changes in streamline direction near a filter fibre, this happens. Because of its inertia, the particle will continue on its original course and collide with the filter fibre. When high gas velocities and dense fibre packing of the filter media are present, this sort of filtration mechanism is most prevalent.
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This question is part of the following fields:
- Anaesthesia Related Apparatus
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Question 8
Incorrect
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An 85-year old female is being investigated and treated for pancytopenia of unknown origin. Her most recent blood test is shown below which shows that he has a low platelet count. Hb-102 g/l, WBC - 2.9* 109/l, Platelets - 7 * 109/l. Which of the following normally stimulates platelet production?
Your Answer: Granulocyte-colony stimulating factor
Correct Answer: Thrombopoietin
Explanation:Interleukin-4 is a cytokine which acts to regulate the responses of B and T cells.
Erythropoietin is responsible for the signal that initiated red blood cell production.
Granulocyte-colony stimulating factor stimulates the bone marrow to produce granulocytes.
Interleukin-5 is a cytokine that stimulates the proliferation and activation of eosinophils.
Thrombopoietin is the primary signal responsible for megakaryocyte and thus platelet production.
Platelets are also called thrombocytes. They, like red blood cells, are also derived from myeloid stem cells. The process involves a megakaryocyte developing from a common myeloid progenitor cell. A megakaryocyte is a large cell with a multilobulated nucleus, this grows to become massive where it will then break up to form platelets.Immune cells are generated from haematopoietic stem cells in bone marrow. They generate two main types of progenitors, myeloid and lymphoid progenitor cells, from which all immune cells are derived.
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This question is part of the following fields:
- Physiology And Biochemistry
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Question 9
Correct
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Which of the following best explains the association between smoking and lower oxygen delivery to tissues?
Your Answer: Left shift of the oxygen dissociation curve
Explanation:Smoking is a major risk factor associated with perioperative respiratory and cardiovascular complications. Evidence also suggests that cigarette smoking causes imbalance in the prostaglandins and promotes vasoconstriction and excessive platelet aggregation. Two of the constituents of cigarette smoke, nicotine and carbon monoxide, have adverse cardiovascular effects. Carbon monoxide increases the incidence of arrhythmias and has a negative ionotropic effect both in animals and humans.
Smoking causes an increase in carboxyhaemoglobin levels, resulting in a leftward shift in which appears to represent a risk factor for some of these cardiovascular complications.
There are two mechanisms responsible for the leftward shift of oxyhaemoglobin dissociation curve when carbon monoxide is present in the blood. Carbon monoxide has a direct effect on oxyhaemoglobin, causing a leftward shift of the oxygen dissociation curve, and carbon monoxide also reduces the formation of 2,3-DPG by inhibiting glycolysis in the erythrocyte. Nicotine, on the other hand, has a stimulatory effect on the autonomic nervous system. The effects of nicotine on the cardiovascular system last less than 30 min.
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This question is part of the following fields:
- Physiology
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Question 10
Correct
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A new drug treatment has been developed for Crohn's disease. The pharmaceutical company behind this, is planning to conduct a trial and is looking for hiring around 200 individuals that are suffering from Crohn's disease. The aim would be to determine if there is any decline in the disease activity in response to the drug and compare it with a placebo. What phase is the trial in?
Your Answer: Phase 2
Explanation: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.
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This question is part of the following fields:
- Statistical Methods
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Question 11
Correct
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Which one of the following patients presenting for elective surgery has an American Society of Anaesthesiologists (ASA) preoperative physical status grading of III?
Your Answer: A 50-year old man with a BMI of 41 with a reduced exercise tolerance
Explanation:The ASA physical status classification system is a system for assessing the fitness of patients before surgery. It was last updated in October 2014.
ASA I A normal healthy patient
ASA II A patient with mild systemic disease
ASA III A patient with severe systemic disease
ASA IV A patient with severe systemic disease that is a constant threat to life
ASA V A moribund patient who is not expected to survive without the operation
ASA VI A declared brain-dead patient whose organs are being removed for donor purposesA 20-year old woman who is 39-weeks pregnant with no other medical conditions – ASA II
A 35-year-old man with a BMI of 29 with a good exercise tolerance who smokes-ASA II
A 50-year old man with a BMI of 41 with a reduced exercise tolerance -ASA III
A 65-year old woman with a BMI of 34 with treated hypertension with no functional limitations-ASA II
A 73-year old man who has had a TIA ten-weeks ago but has a good exercise tolerance and is a non-smoker-ASA IV.
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This question is part of the following fields:
- Clinical Measurement
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Question 12
Correct
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A peripheral nerve stimulator is used to stimulate the ulnar nerve at the wrist to indicate the degree of neuromuscular blockade. Which single muscle or group of muscles of the hand supplied by the ulnar nerve is best for monitoring the twitch function during neuromuscular blockade?
Your Answer: Adductor pollicis
Explanation:In anaesthesia, adductor pollicis neuromuscular monitoring with ulnar nerve stimulation is commonly used. It is the gold standard for measuring the degree of block and comparing neuromuscular blocking drugs and their effects on other muscles.
Electrodes are usually placed over the ulnar nerve at the wrist to monitor the adductor pollicis.
Neuromuscular blocking drugs have different sensitivity levels in different muscle groups.
To achieve the same level of blockade, the diaphragm requires 1.4 to 2 times the amount of neuromuscular blocking agent as the adductor pollicis muscle. The small muscles of the larynx and the ocular muscles are two other respiratory muscles that are less resistant than the diaphragm (especially corrugator supercilii).
The abdominal muscles, Orbicularis oculi, peripheral muscles of the limbs, Geniohyoid, Masseter, and Upper airway muscles are the most sensitive to neuromuscular blocking agents.
The C8-T1 nerve roots, which are part of the medial cord of the brachial plexus, form the ulnar nerve. It enters the hand via the ulnar canal, superficial to the flexor retinaculum, after following the ulnar artery at the wrist.
The nerve then splits into two branches: superficial and deep. The palmaris brevis is supplied by the superficial branch, which also provides palmar digital nerves to one and a half fingers. The dorsal surface of the medial/ulnar 1.5 fingers, as well as the corresponding skin over the hand, are also supplied by it (as well as the palmar surface).
The ulnar nerve’s deep branch runs between the abductor and flexor digiti minimi, which it supplies. It also innervates the opponens, and with the deep palmar arch, it curves around the hook of the hamate and laterally across the palm. All of the interossei, the medial two lumbricals, the adductor pollicis, and, in most cases, the flexor pollicis brevis are supplied there.
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This question is part of the following fields:
- Anatomy
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Question 13
Correct
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Which of the following lung parameters can be measured directly using spirometry?
Your Answer: Vital capacity
Explanation:Spirometry measures the total volume of air that can be forced out in one maximum breath, that is the total lung capacity (TLC), to maximal expiration, that is the residual volume (RV).
It is conducted using a spirometer which is capable of measuring lung volumes using techniques of dilution.
During spirometry, the following measurements can be determined:
Forced vital capacity (FVC)/vital capacity (VC): The maximum volume of air exhaled in one single forced breathe.
Forced expiratory volume in one second (FEV1)
FEV1/FVC ratio
Peak expiratory flow (PEF): the maximum amount of air flow exhaled in one blow.
Forced expiratory flow (mid expiratory flow): the flow at 25%, 50% and 75% of FVC
Inspiratory vital capacity (IVC): The maximum volume of air inhaled after a full total expiration.Anatomical dead space is measured using a single breath nitrogen washout called the Fowler’s method.
Residual volume and total lung capacity are both measured using the body plethysmograph or helium dilution
The functional residual capacity is usually measured using a nitrogen washout or the helium dilution technique.
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This question is part of the following fields:
- Clinical Measurement
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Question 14
Correct
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When administered as an infusion, which of the following medicines causes a reflex tachycardia?
Your Answer: Phentolamine
Explanation:The α-2 adrenoceptor has three subtypes (2a, 2b and 2c). The receptors are generally presynaptic, meaning they prevent noradrenaline from being released at nerve endings. Both the central and peripheral nerve systems are affected by the α-2 agonists. α-2 agonists cause drowsiness, analgesia, and euphoria centrally in the locus coeruleus (in the brainstem), lower the MAC of volatile anaesthetic drugs, and are used to treat acute withdrawal symptoms in chronic opioid addicts.
The most common impact of α-2 agonists on heart rate is bradycardia. The adrenoreceptors α-1 and α-2 are blocked by phenoxybenzamine.
Clonidine is a selective agonist for the α -2 receptor, having a 200:1 affinity ratio for the α-2: α-1 receptors, respectively.
Tizanidine is similar to clonidine but has a few key variances. It has the same sedative, anxiolytic, and analgesic characteristics as clonidine, although for a shorter period of time and with less effect on heart rate and blood pressure.
Dexmedetomidine, like clonidine, is a highly selective α-2 adrenoreceptor agonist having a higher affinity for the α-2 receptor. In the case of α-2: α-1 receptors, the affinity ratio is 1620:1. It has a biphasic blood pressure impact and induces a brief rise in blood pressure and reflex bradycardia (activation of α-2b subtypes of receptors in vascular smooth muscles), followed by a reduction in sympathetic outflow from the brainstem and hypotension/bradycardia.
A prodrug is methyldopa. It blocks the enzyme dopa-decarboxylase, which converts L-dopa to dopamine (a precursor of noradrenaline and adrenaline). It is also converted to alpha-methyl noradrenaline, a centrally active agonist of the α-2 adrenoreceptor. These two processes contribute to its blood pressure-lowering effect. Without a rise in heart rate, cardiac output is generally maintained. The heart rate of certain patients is slowed.
Phentolamine is a short-acting antagonist of peripheral α-1 and α-2 receptors that causes peripheral vascular resistance to reduce and vasodilation to increase. It’s used to treat hypertensive situations that aren’t life threatening (e.g. hypertension from phaeochromocytoma).
A baroreceptor reflex commonly causes reflex tachycardia when systemic vascular resistance drops.
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This question is part of the following fields:
- Pharmacology
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Question 15
Correct
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Which statement is true with regards to the cardiac action potential?
Your Answer: Repolarization due to potassium efflux after calcium channels close causes the relative refractory period to start
Explanation: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
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This question is part of the following fields:
- Physiology And Biochemistry
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Question 16
Correct
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An 80-year-old man will be operated on for an arterial bypass procedure to treat claudication and foot ulceration. The anterior tibial artery will be the target for distal arterial anastomosis. Which structure is NOT closely related to the anterior tibial artery?
Your Answer: Tibialis posterior
Explanation:The anterior tibial artery originates from the distal border of the popliteus. In the posterior compartment, it passes between the heads of the tibialis posterior and the oval aperture of the interosseous membrane to reach the anterior compartment.
On entry into the anterior compartment, it runs medially along the deep peroneal nerve.
The upper third of the artery courses between the tibialis anterior and extensor digitorum longus muscles, while the middle third runs between the tibialis anterior and extensor hallucis longus muscles.At the ankle, the anterior tibial artery is located approximately midway between the malleoli. It continues on the dorsum of the foot, lateral to extensor hallucis longus, as the dorsalis pedis artery.
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This question is part of the following fields:
- Anatomy
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Question 17
Incorrect
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Which of the following statements is true regarding ketamine?
Your Answer: Has an R (-) enantiomer which is less psychoactive
Correct Answer: Can be used in the management of refractory status epilepticus
Explanation:Ketamine is a phencyclidine (hallucinogenic) derivative that is administered in a dose of 2 mg/kg and acts by blocking NMDA (N-methyl-D-aspartate) receptors of glutamate.
It is a powerful bronchodilator agent and is, therefore, an intravenous anaesthetic of choice in bronchial asthma (halothane is an inhalational anaesthetic agent of choice for bronchial asthma). It is also used in the management of refractory status epilepticus.
It is an acid solution with an elimination half-life of three hours.
It has S (+) enantiomer and R (-) enantiomer. the S(+) enantiomer is two to four times more potent than the R(-) and is less likely to produce hallucinations.
Its use is contraindicated in patients with ischaemic heart disease because it increased sympathetic outflow leading to tachycardia and increased cardiac output which in turn increases the myocardial oxygen demand.
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This question is part of the following fields:
- Pharmacology
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Question 18
Correct
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Seven days after undergoing an inguinal hernia repair, a 24-year old male presents with a wound that is erythematous, tender and has a purulent discharge. The most likely cause of this is which of the following?
Your Answer: Infection with Staphylococcus aureus
Explanation: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 dressingIn 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 intentionUse 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. -
This question is part of the following fields:
- Physiology And Biochemistry
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Question 19
Incorrect
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Which of the following statements is TRUE regarding an epidural set?
Your Answer: The filter has a 0.55 micron mesh
Correct Answer: 19G Tuohy needles have 0.5 cm markings
Explanation:A paediatric 19G Tuohy catheter is available that is 5cm in length and has 0.5cm markings
18G Tuohy catheters are generally 9 to 10cm to hub
Distal end of catheter is angled (15 to 30 degrees) and closed to avoid puncturing the dura
Epidural mesh are usually 0.2 microns and are used to filter bacteria and viruses to ensure sterility of procedure
Transparent catheters are 90cm long with diameters depending on gauge size. It has 1cm graduations from 5 to 20cm to ensure they have been inserted amply and removed completely. Distal end is smooth which can be open or closed (with lateral openings).
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This question is part of the following fields:
- Anaesthesia Related Apparatus
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Question 20
Incorrect
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A 30-year-old man has been stabbed in an area of the groin that contains the femoral triangle. He will undergo explorative surgery. Which of the following makes the lateral wall of the femoral triangle?
Your Answer: Conjoint tendon
Correct Answer: Sartorius
Explanation:The femoral triangle is a wedge-shaped area found within the superomedial aspect of the anterior thigh. It is a passageway for structures to leave and enter the anterior thigh.
Superior: Inguinal ligament
Medial: Adductor longus
Lateral: Sartorius
Floor: Iliopsoas, adductor longus and pectineusThe contents include: (medial to lateral)
Femoral vein
Femoral artery-pulse palpated at the mid inguinal point
Femoral nerve
Deep and superficial inguinal lymph nodes
Lateral cutaneous nerve
Great saphenous vein
Femoral branch of the genitofemoral nerve. -
This question is part of the following fields:
- Anatomy
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Question 21
Correct
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Which of the following is the best marker of mast cell degranulation in a patient with suspected anaphylaxis who became hypotensive and developed widespread urticarial rash after administration of Augmentin?
Your Answer: Tryptase
Explanation:Mast cell tryptase is a reliable marker of mast cell degranulation. Tryptase is a protease enzyme that acts via widespread protease-activated receptors (PARs).
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This question is part of the following fields:
- Pharmacology
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Question 22
Incorrect
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Which of the following statements is true with regards to the Krebs' cycle (also known as the tricarboxylic acid cycle or citric acid cycle)?
Your Answer: Pyruvate condenses with oxaloacetate to form citrate
Correct Answer: Alpha-ketoglutarate is a five carbon molecule
Explanation:Krebs’ cycle (tricarboxylic acid cycle or citric acid cycle) is a sequence of reactions in which acetyl coenzyme A (acetyl-CoA) is metabolised and this results in carbon dioxide and hydrogen atoms production.
This series of reactions occur in the mitochondria of eukaryotic cells, not the cytoplasm. The cycle requires oxygen and so, cannot function under anaerobic conditions.
It is the common pathway for carbohydrate, fat and some amino acids oxidation and is required for high energy phosphate bond formation in adenosine triphosphate (ATP).
When pyruvate enters the mitochondria, it is converted into acetyl-CoA. This represents the formation of a 2 carbon molecule from a 3 carbon molecule. There is loss of one CO2 but formation of one NADH molecule. Acetyl-CoA is condensed with oxaloacetate, the anion of a 4 carbon acid, to form citrate which is a 6 carbon molecule.
Citrate is then converted into isocitrate, alpha-ketoglutarate, succinyl-CoA, succinate, fumarate, malate and finally oxaloacetate.
The only 5 carbon molecule in the cycle is alpha-ketoglutarate.
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This question is part of the following fields:
- Physiology
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Question 23
Correct
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A 42-year-old man presented with a bitemporal hemianopia with enlarged hands and feet. On examination, he was found to be hypertensive. Which of the following correctly explains the cause of his visual field defect?
Your Answer: Pituitary macroadenoma secreting growth hormone (GH)
Explanation:Pituitary macroadenoma is a benign tumour with growth larger than 10mm (those under 10mm are called microadenoma)
Compression of optic chiasm by pituitary adenoma is responsible for causing visual field defects like bitemporal hemianopia, optic neuropathy.
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This question is part of the following fields:
- Pathophysiology
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Question 24
Correct
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A 60-year-old man had previously been diagnosed with Type 2 diabetes. He had recently started gliclazide, a sulphonyl urea, as his diabetes was not controlled by metformin alone. Now, he presents to his physician with complaints of anxiety, sweating, and palpitations since the morning. On physical examination, he is pale and clammy and has mydriasis and increased bowel sounds. Which biological site primarily synthesizes the hormone responsible for this patient's condition?
Your Answer: Chromaffin cells of the adrenal medulla
Explanation:This patient has been shifted to a sulfonylurea drug whose most common side effect is hypoglycaemia. Similar symptoms can arise in a patient on insulin too. The signs and symptoms are consistent with a hypoglycaemic attack and include tachycardia, altered consciousness, and behaviour. This needs to be treated as an emergency with rapid correction of the blood glucose level using glucose or IV 20% dextrose.
In a hypoglycaemic attack, the body undergoes stress and releases hormones to increase blood glucose levels. These include:
Glucagon
Cortisol
AdrenalineAdrenaline or epinephrine is the hormone responsible for this patient’s condition and is primarily produced in the medulla of the adrenal gland. It functions primarily to raise cardiac output and raise blood glucose levels in the blood.
Alpha-cells of the islets of Langerhans produce the hormone glucagon, which has opposing effects to insulin.
Follicular cells of the thyroid gland produce and secrete thyroid hormones. Thyroid hormones can cause similar symptoms, but it is unlikely with the patient’s medical history.
Post-ganglionic neurons of the sympathetic nervous system use norepinephrine as a neurotransmitter. Adrenaline can be made in these cells, but it is not their primary production site.
Zona fasciculata of the adrenal cortex is the main site for the production of cortisol.
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This question is part of the following fields:
- Anatomy
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Question 25
Correct
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Given the following values: Expired tidal volume = 800 ml, Plateau pressure = 50 cmH2O, PEEP = 10 cmH2O. Compute for the static pulmonary compliance.
Your Answer: 20 ml/cmH2O
Explanation:Compliance of the respiratory system describes the expandability of the lungs and chest wall. There are two types of compliance: dynamic and static.
Dynamic compliance describes the compliance measured during breathing, which involves a combination of lung compliance and airway resistance. Defined as the change in lung volume per unit change in pressure in the presence of flow.
Static compliance describes pulmonary compliance when there is no airflow, like an inspiratory pause. Defined as the change in lung volume per unit change in pressure in the absence of flow.
For example, if a person was to fill the lung with pressure and then not move it, the pressure would eventually decrease; this is the static compliance measurement. Dynamic compliance is measured by dividing the tidal volume, the average volume of air in one breath cycle, by the difference between the pressure of the lungs at full inspiration and full expiration. Static compliance is always a higher value than dynamic
Static compliance can be computed using the formula:
Cstat = Tidal volume/Plateau pressure – PEEP
Substituting the values given,
Cstat = 800/50-10
Cstat = 20 ml/cmH2O -
This question is part of the following fields:
- Physiology
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Question 26
Correct
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Among the different classes of anti-arrhythmics, which one is the first line treatment for narrow complex AV nodal re-entry tachycardia?
Your Answer: Adenosine
Explanation:Adenosine is the first line for AV nodal re-entry tachycardia. An initial dose of 6 mg is given, and a consequent second dose or third dose of 12 mg is administered if the initial dose fails to terminate the arrhythmia.
Aside from Adenosine, a vagal manoeuvre (e.g. carotid massage) is done to help terminate the supraventricular arrhythmia.
Amiodarone is not a first-line drug for supraventricular tachycardias. Digoxin and Propranolol can be considered if the arrhythmia is of a narrow complex irregular type. Verapamil is an alternative to Adenosine if the latter is contraindicated.
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This question is part of the following fields:
- Pharmacology
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Question 27
Incorrect
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Regarding the classification of breathing systems, which of the following is true?
Your Answer: The Bain is a coaxial version of the Magill
Correct Answer: The Conway classification describes a functional classification based on whether a CO2 absorber is required
Explanation: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 absorberWilliam 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. -
This question is part of the following fields:
- Anaesthesia Related Apparatus
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Question 28
Correct
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Blood pressure monitoring is a requirement for in-patient care. Different factors can result in an inaccurate blood pressure reading, including the damping of an arterial waveform. How does a damped arterial waveform affect blood pressure measurements?
Your Answer: The systolic pressure is lower and the diastolic pressure higher with the same mean
Explanation:Damping is the reduction of energy in a system achieved by reducing the amplitude of oscillations. It is necessary to some degree to prevent wave overshoots.
Critical damping usually causes the system to be slow, so optimal damping is normally applied to provide a balance between speed and distortion.
Damping can cause errors if excessive (overdamping) or inadequate (Underdamping). The amount of damping in a system can be determined using the damping coefficient (D), where:
Undamped: 0
Critically damped: 1
Optimally damped: 0.64An overdamped system will cause an artificial decrease in the systolic blood pressure, and an artificial increase in the diastolic blood pressure.
An underdamped system will cause an artificial increase in systolic blood pressure and an artificial decrease in diastolic blood pressure.
Damping can be caused by a number of factors affecting different parts of the system, including:
The tubing/cannula: The presence of air bubbles, increased blood viscosity or formation of blood clots.
The diaphragm/tubing: Increased malleability/compliance
The tubing: Presence of kinks, narrowing or too many ports of injection.The answer here is a damped system will have a low systolic pressure, a high diastolic pressure with a normal mean pressure.
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This question is part of the following fields:
- Clinical Measurement
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Question 29
Incorrect
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A 64-year-old man is admitted to the critical care unit. He has a recent medical history of faecal peritonitis for which a laparotomy was performed. His vitals have been monitored using an invasive pulmonary artery flotation catheter. His vital readings are: Temperature: 38.1°C. Blood pressure: 79/51 mmHg (mean 58 mmHg), Pulmonary artery pressure: 19/6 mmHg (mean 10 mmHg). Pulmonary capillary occlusion pressure: 5 mmHg, Central venous pressure: 12 mmHg, Cardiac output: 5 L/min, Mixed venous oxygen saturation: 82%. Calculate his approximate pulmonary vascular resistance. Note: A correction factor of 80 is require to convert mmHg to dynes·s·cm-5
Your Answer: 100 dynes·s·cm-5
Correct Answer: 80 dynes·s·cm-5
Explanation:Pulmonary vascular resistance (PVR) refers to the resistance to blood flow to the left atrium from the pulmonary artery.
It is derived mathematically by:PVR = MPAP – PCWP
CO
where,
MPAP: Mean pulmonary artery pressure
PCWP: Pulmonary capillary occlusion pressure
CO: Cardiac outputFor this patient:
PVR = 10 – 5 = 1mmHg
5Remember, multiply by correction factor 80 to change units:
PVR = 1mmHg x 80 = 80 dynes·s·cm-5
Normal values range between 20-130 dynes·s·cm-5.
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This question is part of the following fields:
- Clinical Measurement
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Question 30
Incorrect
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A human's resting oxygen consumption (VO2) is typically 3.5 ml/kg/minute (one metabolic equivalent or 1 MET). Which of the following options is linked to the highest VO2 when a person is at rest?
Your Answer: Dobutamine infusion in a fit adult
Correct Answer: Neonate
Explanation:The oxygen consumption rate (VO2) at rest is 3.5 ml/kg/minute (one metabolic equivalent or 1 MET).
3.86 ml/kg/minute thyrotoxicosisYoung children consume a lot of oxygen: around 7 ml/kg/min when they are born. The metabolic cost of breathing is higher in children than in adults, and it can account for up to 15% of total oxygen consumption. Similarly, an infant’s metabolic rate is nearly twice that of an adult, resulting in a larger alveolar minute volume and a lower FRC.
At term, oxygen consumption at rest can increase by as much as 40% (5 ml/kg/minute) and can rise to 60% during labour.
When compared to normal basal metabolism, sepsis syndrome increases VO2 and resting metabolic rate by 30% (4.55 ml/kg/minute). In septicaemic shock, VO2 decreases.
Dobutamine hydrochloride was infused into 12 healthy male volunteers at a rate of 2 micrograms per minute per kilogramme, gradually increasing to 4 and 6 micrograms per minute per kilogramme. Dobutamine was infused for 20 minutes for each dose. VO2 increased by 10% to 15%. (3.85-4.0 ml/kg/min).
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This question is part of the following fields:
- Physiology
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