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Question 1
Incorrect
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When compared to unipolar diathermy, which of the following is more specific to bipolar diathermy?
Your Answer: Has a frequency of 500 KHz - 1 MHz
Correct Answer: Has a power output of up to 140 joules per second
Explanation:Electrocautery, also known as diathermy, is a technique for coagulation, tissue cutting, and fulguration that uses a high-frequency current to generate heat (cell destruction from dehydration).
The two electrodes in bipolar diathermy are the tips of forceps, and current passes between the tips rather than through the patient. Bipolar diathermy’s power output (40-140 W) is lower than unipolar diathermy’s typical output (400 W). There is no earthing in the bipolar circuit.
A cutting electrode and a indifferent electrode in the form of a metal plate are used in unipolar diathermy. The high-frequency current completes a circuit by passing through the patient from the active electrode to the metal plate. When used correctly, the current density at the indifferent electrode is low, and the patient is unlikely to be burned. Between the patient plate and the earth is placed an isolating capacitor. This has a low impedance to a high frequency current, such as diathermy current, and is used in modern diathermy machines. The capacitor has a high impedance to current at 50 Hz, which protects the patient from electrical shock.
High frequency currents (500 KHz – 1 MHz) are used in both unipolar and bipolar diathermy, which can cause tissue damage and interfere with pacemaker function (less so with bipolar diathermy).
The effect of diathermy is determined by the current density and waveform employed. The current is a pulsed square wave pattern in coagulation mode and a continuous square wave pattern in cutting mode.
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This question is part of the following fields:
- Anaesthesia Related Apparatus
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Question 2
Correct
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A patient has a myocardial infarction with anterior ST elevation. There are the following observations: Cardiac output 2.0 L/min, Blood pressure 80/60 mmHg, CVP 20 mmHg, SpO2 91% on 4 L/min oxygen. What is the most logical physiological explanation for these findings?
Your Answer: Biventricular failure
Explanation:The occlusion of the left anterior descending (LAD) coronary artery causes anterior ST elevation myocardial infarction (STEMI). It has the worst prognosis of all the infarct locations due to its larger infarct size. It has a higher rate of total mortality (27 percent versus 11 percent), heart failure (41 percent versus 15 percent), and a lower ejection fraction on admission than an inferior myocardial infarction (38 percent versus 55 percent ).
The LAD artery supplies the majority of the interventricular septum, as well as the anterior, lateral, and apical walls of the left ventricle, as well as the majority of the right and left bundle branches and the bicuspid valve’s anterior papillary muscle (left ventricle).
The left or right ventricle’s end-diastolic volume (EDV) is the volume of blood in each chamber at the end of diastole before systole. Preload is synonymous with the EDV.
120 mL is a typical left ventricular EDV (range 65-240 mL). The EDV of the right ventricle in a typical range is (100-160 mL).
With an ejection fraction (EF) of less than 45 percent, the patient is most likely suffering from systolic dysfunction. Increases in right and left ventricular end-diastolic pressures and volumes are likely with a reduced EF because the ventricles are not adequately emptied. The left atrium and the pulmonary vasculature are affected by the increased pressures on the left side of the heart.
By causing an imbalance of the Starling forces acting across the capillaries, increased hydrostatic pressure in the pulmonary circulation favours the development of pulmonary oedema. With cardiogenic pulmonary oedema, capillary permeability is likely to remain unchanged.
Biventricular failure will result as a result of the pressure changes being transmitted to the right side of the circulation. The patient’s systemic vascular resistance is likely to be elevated as well, but it is not the most likely cause of his symptoms. The patient is suffering from cardiogenic shock as a result of biventricular failure. The patient has low cardiac output and is hypotensive. Right ventricular filling pressures are elevated, indicating right ventricular dysfunction.
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This question is part of the following fields:
- Clinical Measurement
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Question 3
Incorrect
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One litre of water at 0°C and a pressure of 1 bar is in a water-bath. A 1 kW element is used in heating it. Given that the specific heat capacity of water is 4181 J/(kg°C) or J/(kg K), how long will it take to raise the temperature of the water by 10°C?
Your Answer: 7 minutes
Correct Answer: 42 seconds
Explanation:The amount of energy required to change the temperature of 1 kg of a substance by 1°C is its specific heat capacity.
Energy required to increase the temperature of any object is given by the equation:
E = m × c × θ
Where:
E = energy required to heat an object
m = mass of object
c = specific heat capacity of the substance
θ = temperature changeThe specific heat capacity of water is 4181 J/(kg°C)
Therefore the energy required to raise 1kg of water by 10°C is:
1 kg × 4181 J/(kg°C) × 10°C = 41810 J
A 1 kW or 1000 W heater would be expected to supply 1000 J/s.
The approximate time it would take the 1 kW heater to raise the temperature of one Litre of water by 10°C is:
41810/1000 = 41.8 seconds.
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This question is part of the following fields:
- Physiology
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Question 4
Correct
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The plateau phase of the myocardial action potential is as a result of:
Your Answer: Slow influx of calcium
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 5
Correct
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Regarding the treatment of bladder cancer, a study concerned with the usage of a combined or monotherapy was conducted. A forest plot was used for the visual representation of the data. Which of the following is true regarding forest plots?
Your Answer: Forest plots can present data from multiple studies
Explanation:Being the part of a meta analysis, forest plots are more valued as evidence then randomised control trials.
The notion that forest plots can only be used if the results are substantial is not true. They are good indicators of the significance of the data. If the diamond intersects the central line, the data is rendered significant. It also aggregates means and confidence intervals from studies conducted in the past which makes the study much more reliable as errors associated with individual studies tend to have less of an impact in this way.
The suggestion that forest plots are primarily used for qualitative data is factually incorrect. Forest plots require numerical values to function.
All in all, forest plots help us in determining whether or not there is a significant trend in that particular field of study.
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This question is part of the following fields:
- Statistical Methods
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Question 6
Correct
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Which of these structures will cause the biggest reduction in hepatic blood flow when occluded surgically?
Your Answer: Portal vein
Explanation:The portal vein arises from the splenic and mesenteric veins, and is the biggest vessel in the portal venous system, accounting for about 75% of the hepatic blood flow.
It is responsible for draining blood from parts of the gastrointestinal system, the spleen, the pancreas and the gallbladder into the liver.
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This question is part of the following fields:
- Anatomy
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Question 7
Correct
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Which of the following statement is true or false regarding to the respiratory tract?
Your Answer: The sympathetic innervation of the bronchi is derived from T2 - T4
Explanation: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.
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This question is part of the following fields:
- Physiology
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Question 8
Incorrect
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Which of the following ionic changes is associated with the ventricular myocyte action potential's initial repolarization phase?
Your Answer: Decreased Ca2+ and increased K+ conductance
Correct Answer: Ceased Na+ and increase K+ conductances
Explanation:The Purkinje system, as well as the action potentials of ventricular and atrial myocytes, have the same ionic changes. It lasts about 200 milliseconds and has a resting membrane potential, as well as fast depolarisation and plateau phases.
There are five stages to the process:
Increased Na+ and decreased K+ conductance in Phase 0 (rapid depolarisation).
1st phase (initial repolarisation) : Na+ conductance decreased, while K+ conductance increased.
Phase two (plateau phase) : Ca2+ conductance increased
Phase three (repolarisation phase) : Lower Ca2+ conductance and higher K+ conductance
4th Phase (resting membrane potential) : K+ conductance increased, Na+ conductance decreased, and Ca2+ conductance decreased. -
This question is part of the following fields:
- Pathophysiology
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Question 9
Incorrect
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Following an acute appendicectomy, a 6-year-old child is admitted to the recovery unit. Your consultant has requested that you prescribe maintenance fluids for the next 12 hours. The child is 21 kg in weight. What is the most suitable fluid volume to be prescribed?
Your Answer: 610 ml
Correct Answer: 732 ml
Explanation:After a paediatric case, you’ll frequently have to calculate and prescribe maintenance fluids. The ‘4-2-1 rule’ should be used as a guideline:
1st 10 kg – 4 ml/kg/hr
2nd 10 kg – 2 ml/kg/hr
Subsequent kg – 1 ml/kg/hrHence
1st 10 kg = 4 × 10 = 40 ml
2nd 10 kg = 2 × 10 = 20 ml
Subsequent kg = 1 × 1 = 1 ml
Total = 61 ml/hr61 × 12 = 732 ml over 12 hrs.
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This question is part of the following fields:
- Physiology
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Question 10
Correct
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Which compound of ketamine hydrochloride has the most significant anaesthetic property or effect?
Your Answer: (S)-ketamine
Explanation:Ketamine is usually used as a racemic mixture, i.e. (R/S)-ketamine. For over 20 years, use of the more potent (S)-enantiomer by anaesthesiologists has become a preferred option due to the assumption of increased anaesthetic and analgesic properties, a more suitable control of anaesthesia, and of an improved recovery from anaesthesia.
The use of ketamine in anaesthesia and psychiatry may be accompanied by the manifestation of somatic and especially psychomimetic symptoms such as perceptual disturbances, experiences of dissociation, euphoria, and anxiety.
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This question is part of the following fields:
- Pharmacology
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Question 11
Incorrect
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Of the following, which is NOT a branch of the external carotid artery?
Your Answer: Maxillary artery
Correct Answer: Mandibular artery
Explanation: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. -
This question is part of the following fields:
- Anatomy
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Question 12
Correct
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In North America, there have been reports of paediatric patients dying after undergoing adenotonsillectomy for obstructive sleep apnoea. Respiratory depression/obstruction is thought to be the cause of death. The codeine dose was 0.5-1 mg/kg, given every 4-6 hours. In this group of patients, which of the following is the most likely cause of respiratory depression and obstruction?
Your Answer: Exaggerated metabolism of codeine
Explanation:Codeine is easily absorbed from the gastrointestinal tract and converted to morphine and norcodeine in the liver via O- and N-demethylation. Morphine and norcodeine are excreted almost entirely by the kidney, primarily as conjugates with glucuronic acid.
By glucuronidation, phase II metabolism enzyme UDP-glucuronosyl transferase-2B7 converts morphine to morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) (UGT2B7).
Approximately 60% of morphine is converted to M3G, with the remaining 6-10% converted to M6G. M3G is inactive, but M6G is said to be 4 to 650 times more potent on the MOP receptor than morphine.
When codeine is consumed, cytochrome P450 2D6 in the liver converts it to morphine (CYP2D6).
Some people have DNA variations that increase the activity of this enzyme, causing codeine to be converted to morphine more quickly and completely than in others. After taking codeine, these ultra-rapid metabolisers are more likely to have higher than normal levels of morphine in their blood.
Respiratory depression/obstruction can be caused by high levels of morphine and M6G, especially in people who have a history of obstructive sleep apnoea. The estimated number of ultra-rapid metabolisers ranges from 1 to 7 per 100 people, but some ethnic groups may have as many as 28 per 100 people.
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This question is part of the following fields:
- Pathophysiology
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Question 13
Correct
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Regarding the use of soda lime as part of a modern circle system with a vaporiser outside the circuit (VOC), which of the following is its most deleterious consequence?
Your Answer: Carbon monoxide formation
Explanation:When using dry soda lime for VOCs, very high amounts of carbon monoxide may be produced, regardless of the inhalational anaesthetic agent used. The carbon monoxide produced is sufficient enough to cause cytotoxic and anaemic hypoxia. To prevent this, soda lime canisters are shaken well to even out the packing of granules. This can help to evenly distribute gas flow for proper CO2 absorption and ventilation.
Compound A is formed when dry soda lime, or soda lime in high temperature, reacts with the inhalational anaesthetic Sevoflurane. Animal studies have shown renal toxicity in rats, but renal adverse effects in humans are yet to be observed.
When monitors are not employed with VOCs, deleterious effects are not for certain. However, monitors not employed with vaporiser inside the circuit (VIC) can lead to significant adverse events.
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This question is part of the following fields:
- Pathophysiology
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Question 14
Correct
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Useful diagnostic information can be obtained from measuring the osmolality of biological fluids. Of the following physical principles, which is the most accurate and reliable method of measuring osmolality?
Your Answer: Depression of freezing point
Explanation:Colligative properties are properties of solutions that depend on the number of dissolved particles in solution. They do not depend on the identities of the solutes.
All of the above have colligative properties with the exception of depression of melting point.
The osmolality from the concentration of a substance in a solution is measured by an osmometer. The freezing point of a solution can determines concentration of a solution and this can be measured by using a freezing point osmometer. This is applicable as depression of freezing point is directly correlated to concentration.
Vapour pressure osmometers, which measure vapour pressure, may miss certain volatiles such as CO2, ammonia and alcohol that are in the solution
The use of a freezing point osmometer provides the most accurate and reliable results for the majority of applications.
Colligative properties does not include melting point depression . Mixtures of substances in which the liquid phase components are insoluble, display a melting point depression and a melting range or interval instead of a fixed melting point.
The magnitude of the melting point depression depends on the mixture composition.
The melting point depression is used to determine the purity and identity of compounds. EMLA (eutectic mixture of local anaesthetics) cream is a mixture of lidocaine and prilocaine and is used as a topical local anaesthetic. The melting point of the combined drugs is lower than that individually and is below room temperature (18°C).
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This question is part of the following fields:
- Physiology
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Question 15
Incorrect
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Which of the following statements is true regarding ketamine?
Your Answer: It is contraindicated for epidural administration
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 16
Correct
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A 72-year old farmer is hospitalized with acute respiratory failure and autonomic dysfunction. Suspected organophosphate poisoning. Which one is the best mechanism for acute toxicity caused by organophosphates?
Your Answer: Inhibition of acetylcholinesterase
Explanation:The toxicity of organophosphorus (OP) nerve agents is manifested through irreversible inhibition of acetylcholinesterase (AChE) at the cholinergic synapses, which stops nerve signal transmission, resulting in a cholinergic crisis and eventually death of the poisoned person. Oxime compounds used in nerve agent antidote regimen reactivate nerve agent-inhibited AChE and halt the development of this cholinergic crisis.
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This question is part of the following fields:
- Physiology
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Question 17
Incorrect
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Among the following, which statement is true regarding electrical safety in an operation theatre?
Your Answer: Class III equipment are double-insulated
Correct Answer: The higher the frequency of the current the less risk to the patient
Explanation:The operating theatre is an unusual place with several applications of electrical equipment to the human body. This can lead to potential dangers associated with it that need to be prevented. Electrical safety in the operation theatre is the understanding of how these potential dangers can occur and how they can be prevented.
Electricity can cause morbidity or mortality by one of the following ways:
(i) electrocution
(ii) burns
(iii) ignition of a flammable material, causing a fire or explosion.Electrocution is dependant on factors like duration of contact with electric current, the current pathway and the frequency and size of current.
Option A: The higher the frequency, the less effects of electrocution on the body.
Option B & D: Equipment can be classified in classes and types.
The class designation describes the method used for protection against electrocution. Class I is basic protection, class II is double insulation and class III is safety extra low voltage.
The type designation describes the degree of protection based on the maximum permissible leakage currents under normal and fault conditions.
Type B:
can be class I, II or III but the maximum leakage current must not exceed 100 µA. It is therefore not suitable for direct connection to the heart.
Type BF
Similar to type B, but uses an isolated (or floating) circuit.
Type CF
Only type CF protect against microshock as they allow leakage currents of 0.05 mA per electrode for class I and 0.01 mA for class II. Microshock is a small leakage current that can cause harm because of direct connection to the heart via transvenous lines or wires, bypassing the impedance of the skin, leading to ventricular fibrillation. Microshock current of 100 μA is sufficient to cause VF.Option C: A 75mA electrocution can cause ventricular fibrillation. Use the following as a general guide to understand the effect of current size on the body.
1 mA – tingling pain
5 mA – pain
15 mA – tonic muscular contraction
50 mA – respiratory muscle paralysis
75 mA – ventricular fibrillation.Option E: Wet skin reduces the resistance to current flow and therefore increases the effects of electrocution.
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This question is part of the following fields:
- Anaesthesia Related Apparatus
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Question 18
Incorrect
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A 73-year-old woman is admitted to the coronary care unit. She has been diagnosed with an acute myocardial infarction and has gone into a cardiogenic shock. As part of her treatment, she is prescribed a dobutamine infusion and placed on full haemodynamic monitoring. Over the next four days, her measurement are: Day1 Day2 Day3 Day4 Infusion rate of dobutamine (mcg/kg/min): 5, 10, 15, 25. Cardiac output (L/min): 3.4, 3.2, 3.1, 3.2. Pulse rate (beats/min): 110, 112, 105, 100. Blood pressure (mmHg): 80/60, 75/61, 83/60, 81/56. Haemodynamic changes are noted as a result of response to treatment. What is the most probable cause?
Your Answer: Tachyphylaxis secondary to depletion of neurotransmitters
Correct Answer: Tolerance by down-regulation of beta1 receptors
Explanation:Tachyphylaxis is the swiftly declining response to successive drug doses which vastly reduces its effectiveness in a short space of time, mostly as a result of an acute consumption of neurotransmitters.
Tolerance or desensitisation is the slow decline in a person’s reaction to a drug due to continued use. It requires a longer time span than tachyphylaxis, usually over days or weeks.
Down- regulation is a reduction in the amount of receptors available on target cells which decreases the affinity of the agent to the cells. For this to occur, the down-regulation of receptors must occur at a rate faster than receptor synthesis. This down-regulation often occurs with beta1 receptors due to:
1) The transportation or receptors from the cell surface to the interior of the cell
2) Degradation of receptors occurring over time.
In this case, dobutamine is prescribed to treat cardiogenic shock. It is able to function by binding to beta1-adrenergic receptors to increase the contraction of the heart, thereby improving cardiac output. It also binds to beta2- and alpha1-adrenergic receptors to balance out the effects produced by binding to beta1 receptors and reduce the risk of system vasculature responses.
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This question is part of the following fields:
- Clinical Measurement
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Question 19
Correct
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With regards to this state of matter which has a volume but no definite shape, particles are not tightly packed together. These are incompressible although there is free movement within the volume. This statement best describes which one of the following states of matter?
Your Answer: Liquid
Explanation:The solid state of matter has a definite volume and shape and particles are packed closely together and are incompressible. Within this tight lattice, there is enough thermal energy to produce vibration of particles.
Liquids however have a volume but no definite shape. These particles are less tightly packed together. Although there is free movement within the volume, they are incompressible.
Gases, however, have no finite shape or volume and particles are free to move rapidly in a state of random motion. They are compressible and are completely shaped by the space in which they are held. Vapours exist as a gas phase in equilibrium with identical liquid or solid matter below its boiling point.
The most prevalent state of matter in the universe is plasma which is formed by heating atoms to very high temperatures to form ions.
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This question is part of the following fields:
- Basic Physics
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Question 20
Incorrect
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A bolus of alfentanil has a faster onset of action than an equal dose of fentanyl. Which of the following statements most accurately describes the difference?
Your Answer: The volume of distribution of alfentanil is less than fentanyl
Correct Answer: The pKa of alfentanil is less than that of fentanyl
Explanation:Unionised molecules are more likely than ionised molecules to cross membranes (such as the blood-brain barrier).
Because alfentanil and fentanyl are weak bases, the Henderson-Hasselbalch equation says that the ratio of ionised to unionised molecules is determined by the parent compound’s pKa in relation to physiological pH.
Alfentanil has a pKa of 6.5, while fentanyl has a pKa of 8.4.
At a pH of 7.4, 89 percent of alfentanil is unionised, whereas 9% of fentanyl is.As a result, alfentanil has a faster onset than fentanyl.
Fentanyl is 83% plasma protein bound
Alfentanil is 90% plasma protein bound.Alfentanil’s pharmacokinetics are affected by its higher plasma protein binding. Because alfentanil has a low hepatic extraction ratio (0.4), clearance is determined by the degree of protein binding rather than the time it takes to take effect.
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This question is part of the following fields:
- Pharmacology
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