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ANZCA Primary practice questions

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Question 1Anaesthesia

A 70 kg adult is receiving a volatile anaesthetic. Which agent has the lowest blood:gas partition coefficient?

  1. Desflurane Correct answer.
  2. Halothane
  3. Isoflurane
  4. Sevoflurane

Explanation

The blood:gas partition coefficient reflects solubility in blood; a lower value means faster equilibration between alveolar gas and arterial blood, giving quicker induction and recovery. Desflurane has the lowest blood:gas coefficient of the commonly used volatile agents, followed by sevoflurane, isoflurane and halothane.

Question 2Anaesthesia

Which volatile anaesthetic is most associated with dose-dependent bronchodilation and is therefore often chosen for patients with reactive airways?

  1. Desflurane
  2. Halothane
  3. Nitrous oxide
  4. Sevoflurane Correct answer.

Explanation

Sevoflurane is non-pungent, permits smooth inhalational induction, and produces bronchodilation, making it a common choice in reactive airway disease. Desflurane is pungent and airway-irritant, and nitrous oxide is not a potent bronchodilator.

Question 3Anaesthesia

What is the approximate minimum alveolar concentration (MAC) of sevoflurane in a healthy young adult?

  1. 0.75%
  2. 6%
  3. 0.2%
  4. 2% Correct answer.

Explanation

MAC is the alveolar concentration at which 50% of patients do not move in response to a standard surgical stimulus. Sevoflurane has a MAC of approximately 2% in young adults, which rises in the elderly and falls with hypothermia and pregnancy.

Question 4Anaesthesia

Which intravenous induction agent is a non-barbiturate imidazole derivative that produces dose-dependent hypotension primarily through vasodilation and myocardial depression?

  1. Etomidate
  2. Ketamine
  3. Thiopentone
  4. Propofol Correct answer.

Explanation

Propofol is an imidazole derivative whose induction dose commonly causes hypotension via decreased systemic vascular resistance and some myocardial depression. This is exaggerated in hypovolaemia and the elderly, so doses are reduced in those groups.

Question 5Anaesthesia

A patient with severe hypovolaemia from a ruptured aortic aneurysm requires induction. Which induction agent best preserves haemodynamic stability?

  1. Etomidate Correct answer.
  2. Sevoflurane at 2 MAC
  3. Propofol
  4. Thiopentone

Explanation

Etomidate produces minimal cardiovascular depression and is therefore preferred when haemodynamic reserve is poor. Propofol and thiopentone both cause significant vasodilation and myocardial depression, and high-MAC volatile induction worsens hypotension.

Question 6Anaesthesia

Which property of ketamine makes it useful in the shocked trauma patient?

  1. It preserves airway reflexes and sympathetic tone Correct answer.
  2. It is a potent muscle relaxant
  3. It causes profound vasodilation
  4. It reliably prevents emergence delirium

Explanation

Ketamine is a dissociative agent that maintains sympathetic outflow and respiratory drive, preserving blood pressure and airway reflexes better than most other induction agents. However, it can cause emergence phenomena and does not provide muscle relaxation.

Question 7Anaesthesia

Which opioid metabolite accumulates in renal failure and can cause delayed respiratory depression?

  1. Fentanyl
  2. Remifentanil acid
  3. Morphine-6-glucuronide Correct answer.
  4. Naloxone

Explanation

Morphine is metabolised to morphine-6-glucuronide, an active metabolite that is renally cleared. In renal failure it accumulates and can produce prolonged sedation and respiratory depression.

Question 8Anaesthesia

Which opioid is best described as having context-sensitive half-time that is essentially independent of infusion duration?

  1. Morphine
  2. Fentanyl
  3. Alfentanil
  4. Remifentanil Correct answer.

Explanation

Remifentanil is rapidly hydrolysed by non-specific plasma and tissue esterases, so its offset is independent of infusion duration. This makes it ideal for prolonged infusions where rapid recovery is desired.

Question 9Anaesthesia

Which muscle relaxant is metabolised by plasma cholinesterase and has a prolonged duration in patients with atypical pseudocholinesterase?

  1. Rocuronium
  2. Atracurium
  3. Suxamethonium Correct answer.
  4. Vecuronium

Explanation

Suxamethonium is hydrolysed by plasma cholinesterase (pseudocholinesterase). Patients homozygous for the atypical enzyme metabolise it very slowly, producing prolonged paralysis.

Question 10Anaesthesia

Which non-depolarising muscle relaxant undergoes Hofmann elimination, making its duration relatively independent of hepatic and renal function?

  1. Suxamethonium
  2. Pancuronium
  3. Atracurium Correct answer.
  4. Rocuronium

Explanation

Atracurium degrades spontaneously by Hofmann elimination at body temperature and pH, plus ester hydrolysis, so its action is little affected by organ failure. Laudanosine is a metabolite of concern in prolonged infusions.

Question 11Anaesthesia

What is the mechanism of action of neostigmine in reversing non-depolarising neuromuscular blockade?

  1. It directly displaces the relaxant from the receptor
  2. It inhibits acetylcholinesterase, increasing acetylcholine at the neuromuscular junction Correct answer.
  3. It blocks presynaptic acetylcholine release
  4. It increases plasma cholinesterase activity

Explanation

Neostigmine is an acetylcholinesterase inhibitor that increases acetylcholine concentration at the neuromuscular junction, outcompeting the non-depolarising blocker. It is ineffective against depolarising blockade and should be preceded by an antimuscarinic to limit bradycardia.

Question 12Anaesthesia

Which agent is a selective relaxant binding agent used to reverse rocuronium blockade?

  1. Flumazenil
  2. Glycopyrrolate
  3. Neostigmine
  4. Sugammadex Correct answer.

Explanation

Sugammadex is a modified gamma-cyclodextrin that encapsulates rocuronium and vecuronium, rapidly reducing their free concentration and reversing blockade. It can reverse profound blockade that neostigmine cannot.

Question 13Anaesthesia

A patient with a history of malignant hyperthermia susceptibility requires general anaesthesia. Which agent should be avoided?

  1. Remifentanil
  2. Nitrous oxide
  3. Propofol
  4. Sevoflurane Correct answer.

Explanation

Volatile anaesthetics such as sevoflurane and the depolarising relaxant suxamethonium are the classic triggers of malignant hyperthermia. A total intravenous anaesthetic technique is typically used in susceptible patients.

Question 14Anaesthesia

Which is the first-line specific treatment for a malignant hyperthermia crisis?

  1. Sodium bicarbonate
  2. Verapamil
  3. Naloxone
  4. Dantrolene Correct answer.

Explanation

Dantrolene acts on the ryanodine receptor to reduce calcium release from sarcoplasmic reticulum, addressing the underlying pathophysiology. Supportive measures include stopping triggers, cooling, and treating hyperkalaemia and acidosis.

Question 15Anaesthesia

How does a depolarising neuromuscular blocker differ from a non-depolarising blocker at the receptor?

  1. It prevents acetylcholine release from the presynaptic terminal
  2. It competitively blocks the acetylcholine binding site without activating it
  3. It inhibits acetylcholinesterase at the junction
  4. It binds and activates the receptor, producing a sustained depolarisation Correct answer.

Explanation

Suxamethonium binds nicotinic receptors and acts as an agonist, causing a persistent depolarisation that renders the endplate refractory. Non-depolarising agents instead compete with acetylcholine without activating the receptor.

Question 16Anaesthesia

Which local anaesthetic characteristic most determines the speed of onset of a peripheral nerve block?

  1. Lipid solubility
  2. Molecular weight
  3. Protein binding
  4. pKa relative to tissue pH Correct answer.

Explanation

Onset depends on the proportion of drug in the uncharged base form, which crosses the nerve membrane; this is determined by the pKa relative to tissue pH. Lipid solubility mainly determines potency and protein binding determines duration.

Question 17Anaesthesia

Which local anaesthetic is most likely to cause methaemoglobinaemia when used in large doses?

  1. Prilocaine Correct answer.
  2. Lidocaine
  3. Bupivacaine
  4. Ropivacaine

Explanation

Prilocaine's metabolite o-toluidine oxidises haemoglobin to methaemoglobin, which is more likely with large doses. It is treated with methylene blue when clinically significant.

Question 18Anaesthesia

What is the recommended first-line treatment for local anaesthetic systemic toxicity with cardiovascular collapse?

  1. Sodium nitroprusside
  2. Flumazenil
  3. Adrenaline infusion alone
  4. Intravenous lipid emulsion Correct answer.

Explanation

Intravenous lipid emulsion is the specific treatment for severe local anaesthetic systemic toxicity, acting as a lipid sink. It is given alongside standard resuscitation and airway management.

Question 19Anaesthesia

Which maximum dose of lidocaine (with adrenaline) is most appropriate for infiltration in an adult?

  1. 3 mg/kg
  2. 1 mg/kg
  3. 20 mg/kg
  4. 7 mg/kg Correct answer.

Explanation

Lidocaine with adrenaline is commonly limited to about 7 mg/kg in adults, compared with roughly 3 mg/kg for plain lidocaine. The vasoconstrictor slows absorption and reduces peak plasma concentration.

Question 20Anaesthesia

Which receptor type mediates the analgesic and respiratory-depressant effects of opioids?

  1. NMDA receptors
  2. Alpha-2 adrenoceptors
  3. GABA-A receptors
  4. Mu-opioid receptors Correct answer.

Explanation

Mu-opioid receptors are G-protein coupled receptors responsible for analgesia, respiratory depression, euphoria and constipation. Kappa and delta receptors contribute to other effects but mu is the principal target of clinically used opioids.

Question 21Anaesthesia

Which benzodiazepine is commonly used for sedation and has an active metabolite that prolongs its effect, particularly in the elderly?

  1. Midazolam Correct answer.
  2. Remifentanil
  3. Propofol
  4. Dexmedetomidine

Explanation

Midazolam is a short-acting benzodiazepine whose metabolite alpha-hydroxymidazolam is active, and accumulation occurs with prolonged infusion or renal impairment. Its effects are reversed by flumazenil.

Question 22Anaesthesia

Which agent provides sedation and analgesia with minimal respiratory depression and is useful for awake fibreoptic intubation?

  1. Morphine
  2. Propofol
  3. Dexmedetomidine Correct answer.
  4. Suxamethonium

Explanation

Dexmedetomidine is a highly selective alpha-2 agonist producing sedation and analgesia with relatively preserved respiratory drive, making it useful where airway reflexes must be maintained. Bradycardia and hypotension are recognised adverse effects.

Question 23Anaesthesia

A patient is given a large dose of morphine. Which effect is least likely to develop tolerance with chronic opioid use?

  1. Constipation Correct answer.
  2. Respiratory depression
  3. Sedation
  4. Analgesia

Explanation

Tolerance develops to analgesia, sedation, euphoria and respiratory depression with chronic opioid use, but constipation and miosis show little tolerance. This is why constipation requires ongoing prophylaxis.

Question 24Anaesthesia

Which inhalational agent is a potent greenhouse gas with high global warming potential, prompting calls to minimise its use?

  1. Nitrous oxide
  2. Isoflurane
  3. Sevoflurane
  4. Desflurane Correct answer.

Explanation

Desflurane has a very high global warming potential and long atmospheric lifetime, making it the most environmentally damaging commonly used volatile agent. Nitrous oxide also has significant impact but desflurane's potency per unit is far greater.

Question 25Anaesthesia

Which intravenous agent is most appropriate for induction in a patient with known adrenal insufficiency to avoid further suppression of cortisol synthesis?

  1. Thiopentone
  2. Ketamine Correct answer.
  3. Etomidate
  4. Propofol

Explanation

Etomidate inhibits 11-beta-hydroxylase and can suppress adrenal steroidogenesis, which is undesirable in adrenal insufficiency. Ketamine preserves haemodynamics and does not impair cortisol synthesis, making it a reasonable choice.

Question 26Anaesthesia

Which volatile anaesthetic agent has the lowest blood:gas partition coefficient at 37 degrees Celsius?

  1. Sevoflurane
  2. Halothane
  3. Desflurane Correct answer.
  4. Isoflurane

Explanation

The blood:gas partition coefficient determines solubility in blood; a lower value means less agent must be dissolved before alveolar partial pressure rises, so equilibration and induction/recovery are faster. Desflurane has the lowest value of the volatile agents in common use, close to 0.42.

Question 27Anaesthesia

Which volatile agent is most suitable for inhalational induction in a child because it is least pungent and non-irritant to the airway?

  1. Sevoflurane Correct answer.
  2. Enflurane
  3. Desflurane
  4. Isoflurane

Explanation

Sevoflurane is non-pungent, has low airway irritancy and a low blood:gas solubility, making it well tolerated for mask induction in children. Pungent agents provoke coughing, breath-holding and laryngospasm during induction.

Question 28Anaesthesia

What is the standard initial intravenous induction dose of propofol for a healthy young adult?

  1. 2 to 2.5 mg/kg Correct answer.
  2. 5 to 7 mg/kg
  3. 0.1 to 0.2 mg/kg
  4. 0.5 to 1 mg/kg

Explanation

Propofol is typically given at about 2 to 2.5 mg/kg intravenously for induction in a healthy young adult, titrated to effect. The dose should be reduced in the elderly, hypovolaemic or shocked patients because of greater cardiovascular depression.

Question 29Anaesthesia

Which intravenous induction agent is most associated with pain on injection and myoclonus?

  1. Thiopentone
  2. Ketamine
  3. Propofol
  4. Etomidate Correct answer.

Explanation

Etomidate commonly causes pain on injection and involuntary myoclonic movements during induction. It is otherwise haemodynamically stable, which makes it useful in patients with cardiovascular compromise.

Question 30Anaesthesia

Which intravenous induction agent is most appropriate for a haemodynamically unstable patient because it best preserves blood pressure?

  1. Midazolam
  2. Thiopentone
  3. Etomidate Correct answer.
  4. Propofol

Explanation

Etomidate causes minimal cardiovascular depression, maintaining blood pressure and cardiac output, so it is often chosen for induction in shocked or cardiac patients. Its main drawback is adrenal suppression, which matters in sepsis and critical illness.

Question 31Anaesthesia

What is the primary mechanism by which propofol produces anaesthesia?

  1. Antagonism at NMDA receptors
  2. Potentiation of inhibitory GABA-A receptor activity Correct answer.
  3. Agonism at alpha-2 adrenergic receptors
  4. Blockade of voltage-gated sodium channels

Explanation

Propofol enhances the action of the inhibitory neurotransmitter GABA at GABA-A receptors, increasing chloride conductance and neuronal hyperpolarisation. This is the same principal mechanism shared by other intravenous anaesthetics such as thiopentone and etomidate.

Question 32Anaesthesia

Which property of propofol makes it unsuitable as the sole agent for maintenance of anaesthesia during a prolonged procedure requiring muscle relaxation?

  1. It has a slow onset of action
  2. It has no analgesic or muscle relaxant properties Correct answer.
  3. It causes accumulation in adipose tissue
  4. It is a potent trigger of malignant hyperthermia

Explanation

Propofol provides hypnosis and amnesia but has no analgesic or muscle relaxant effect, so opioids and neuromuscular blockers are required as adjuncts. It is not a trigger for malignant hyperthermia.

Question 33Anaesthesia

Which receptor does ketamine principally antagonise to produce its anaesthetic and analgesic effects?

  1. Nicotinic acetylcholine receptor
  2. GABA-A receptor
  3. NMDA receptor Correct answer.
  4. Mu opioid receptor

Explanation

Ketamine is a non-competitive antagonist at the NMDA glutamate receptor, which underlies its dissociative anaesthesia, analgesia and amnesic effects. This mechanism differs from that of most other intravenous anaesthetics.

Question 34Anaesthesia

Which agent is an NMDA receptor antagonist that also provides analgesia and can be used as an adjunct for opioid-sparing in the perioperative period?

  1. Propofol
  2. Rocuronium
  3. Fentanyl
  4. Ketamine Correct answer.

Explanation

Ketamine antagonises NMDA receptors and provides analgesia at sub-anaesthetic doses, so it is used as an opioid-sparing adjunct. Its analgesic effect is distinct from the hypnotic effect of propofol.

Question 35Anaesthesia

Which volatile anaesthetic agent can produce a transient rise in serum fluoride and is associated with nephrotoxicity at high exposure?

  1. Desflurane
  2. Isoflurane
  3. Nitrous oxide
  4. Sevoflurane Correct answer.

Explanation

Sevoflurane is metabolised by the liver to release inorganic fluoride and a compound A, which at high exposure has been linked to renal injury. At conventional fresh gas flows and durations this is rarely clinically significant.

Question 36Anaesthesia

Which effect is a recognised consequence of prolonged nitrous oxide administration?

  1. Direct hepatocellular injury
  2. Irreversible inhibition of plasma cholinesterase
  3. Inactivation of vitamin B12 and interference with methionine synthase Correct answer.
  4. Agonism at GABA-A receptors

Explanation

Nitrous oxide oxidises the cobalt atom in vitamin B12, inactivating methionine synthase and impairing DNA synthesis. Prolonged exposure can cause megaloblastic changes and neurological dysfunction.

Question 37Anaesthesia

Which inhalational agent has the lowest minimum alveolar concentration and is therefore the most potent?

  1. Isoflurane
  2. Halothane Correct answer.
  3. Desflurane
  4. Sevoflurane

Explanation

Minimum alveolar concentration inversely reflects potency; the lower the MAC, the more potent the agent. Halothane has a MAC of about 0.75 percent, lower than the other agents listed.

Question 38Anaesthesia

Which agent is a selective alpha-2 adrenergic agonist used for sedation and analgesia with minimal respiratory depression?

  1. Propofol
  2. Dexmedetomidine Correct answer.
  3. Midazolam
  4. Fentanyl

Explanation

Dexmedetomidine is a highly selective alpha-2 agonist producing sedation and analgesia with little respiratory depression, which makes it useful for awake procedures and intensive care sedation. Bradycardia and hypotension are recognised adverse effects.

Question 39Anaesthesia

Which antiemetic is a 5-HT3 receptor antagonist commonly given for prophylaxis of postoperative nausea and vomiting?

  1. Ondansetron Correct answer.
  2. Droperidol
  3. Metoclopramide
  4. Cyclizine

Explanation

Ondansetron is a selective 5-HT3 receptor antagonist used for prophylaxis and treatment of postoperative nausea and vomiting. It is generally well tolerated, with headache and constipation as common adverse effects.

Question 40Anaesthesia

Which opioid is a partial agonist at the mu receptor and is used as an adjunct for pruritus associated with neuraxial opioid administration?

  1. Fentanyl
  2. Remifentanil
  3. Morphine
  4. Nalbuphine Correct answer.

Explanation

Nalbuphine is a mixed agonist-antagonist with partial mu agonism and kappa agonism, which can treat neuraxial opioid-induced pruritus while maintaining some analgesia. Its antagonist action at mu receptors can precipitate withdrawal in opioid-dependent patients.

Question 41Anaesthesia

Which drug is a competitive antagonist at opioid receptors used to reverse opioid-induced respiratory depression?

  1. Neostigmine
  2. Naloxone Correct answer.
  3. Atropine
  4. Flumazenil

Explanation

Naloxone is a competitive opioid receptor antagonist that reverses opioid-induced respiratory depression and sedation. Because it is short-acting, patients may require repeat dosing or an infusion after long-acting opioids such as morphine.

Question 42Anaesthesia

Which benzodiazepine is reversed by flumazenil?

  1. Ketamine
  2. Dexmedetomidine
  3. Propofol
  4. Midazolam Correct answer.

Explanation

Flumazenil is a competitive antagonist at the benzodiazepine binding site on the GABA-A receptor and reverses drugs such as midazolam and diazepam. It does not reverse propofol, ketamine or dexmedetomidine.

Question 43Anaesthesia

A patient with a known egg allergy requires induction of anaesthesia. Which agent should be avoided because it is formulated in a lipid emulsion containing egg lecithin?

  1. Etomidate
  2. Propofol Correct answer.
  3. Ketamine
  4. Thiopentone

Explanation

The standard propofol formulation contains egg lecithin and soybean oil, so it may be a concern in patients with severe egg allergy. In practice, anaphylaxis to propofol is rare, but an alternative agent is often selected when the allergy is severe.

Question 44Anaesthesia

Which intravenous agent is associated with adrenal suppression and is therefore best avoided as a repeated or prolonged infusion in septic shock?

  1. Thiopentone
  2. Etomidate Correct answer.
  3. Ketamine
  4. Propofol

Explanation

Even a single induction dose of etomidate inhibits 11-beta-hydroxylase and suppresses cortisol synthesis, an effect that is undesirable in critically ill patients such as those with septic shock. Its haemodynamic stability must be weighed against this adrenal effect.

Question 45Anaesthesia

Which mechanism best explains why ketamine increases blood pressure and heart rate in most patients?

  1. Increased circulating acetylcholine
  2. Blockade of cardiac muscarinic receptors
  3. Direct vasoconstriction of arterioles
  4. Sympathetic nervous system stimulation Correct answer.

Explanation

Ketamine stimulates the sympathetic nervous system, increasing catecholamine release and producing tachycardia and hypertension. In catecholamine-depleted patients, its direct myocardial depressant effect can predominate and cause hypotension.

Question 46Anaesthesia

Which agent is most appropriate for sedation of a patient undergoing awake fibreoptic intubation when a spontaneously breathing, cooperative patient is desired?

  1. Dexmedetomidine Correct answer.
  2. Propofol at induction dose
  3. Rocuronium
  4. Suxamethonium

Explanation

Dexmedetomidine provides sedation and analgesia while preserving respiratory drive, which is ideal for awake fibreoptic intubation. Neuromuscular blockers and induction doses of propofol would abolish spontaneous ventilation.

Question 47Anaesthesia

Which property of remifentanil makes it particularly useful for maintenance of anaesthesia during prolonged surgery?

  1. Esterase metabolism giving a context-insensitive offset Correct answer.
  2. Accumulation in adipose tissue
  3. Renal excretion of active metabolites
  4. Hepatic metabolism with a long elimination half-life

Explanation

Remifentanil is metabolised by non-specific plasma and tissue esterases to inactive metabolites, so its offset is rapid and independent of infusion duration. This allows rapid recovery even after prolonged infusion.

Question 48Anaesthesia

Which statement best describes the effect of adding adrenaline to a local anaesthetic solution for infiltration?

  1. It reduces systemic absorption and prolongs the local anaesthetic effect Correct answer.
  2. It shortens the duration of the block
  3. It speeds the onset of the block
  4. It increases the risk of methaemoglobinaemia

Explanation

Adrenaline causes local vasoconstriction, which slows systemic absorption of the local anaesthetic, prolonging its effect and reducing peak plasma concentrations and toxicity. It does not materially speed onset.

Question 49Anaesthesia

Which volatile anaesthetic agent is the most potent greenhouse gas of those in common use, prompting calls to minimise its use?

  1. Isoflurane
  2. Sevoflurane
  3. Halothane
  4. Desflurane Correct answer.

Explanation

Desflurane has a very high global warming potential and a long atmospheric lifetime, far exceeding that of sevoflurane or isoflurane. Because it is also used at high concentrations, its environmental impact per case is substantial.

Question 50Anaesthesia

Which volatile agent is most likely to cause dose-dependent hypotension through vasodilation and myocardial depression?

  1. Nitrous oxide
  2. Desflurane
  3. Isoflurane Correct answer.
  4. Sevoflurane

Explanation

All volatile agents cause dose-dependent cardiovascular depression, but isoflurane produces significant vasodilation and myocardial depression at higher concentrations. Sevoflurane is somewhat more cardiovascularly stable.