NEET PG anaesthesia questions

The blood:gas partition coefficient reflects the solubility of an anaesthetic in blood relative to alveolar gas and determines the speed of induction and recovery. A low blood:gas coefficient means little agent is taken up by blood, so alveolar partial pressure rises quickly, equilibrating rapidly with the brain and producing fast onset; the same property allows rapid washout and recovery. Agents like nitrous oxide, desflurane, and sevoflurane have low coefficients and act quickly, whereas halothane with a higher coefficient has slower onset and recovery.

• A. This describes a high, not low, blood:gas coefficient.
• B. Potency is determined by MAC, not blood:gas solubility.
• D. Fat solubility determines potency and context-sensitive accumulation, not speed of initial onset.

Sevoflurane is the preferred agent for mask induction in children because it has a pleasant, non-pungent odour and does not irritate the airway, allowing smooth induction without coughing, breath-holding, or laryngospasm. It also has a low blood:gas partition coefficient, giving rapid onset, which is desirable when intravenous access has not yet been secured. Desflurane and isoflurane are pungent and cause airway irritation, precluding their use for mask induction, and halothane, though historically used, has largely been replaced due to hepatotoxicity risk and limited availability.

• A. Isoflurane is also pungent and irritates the airway.
• B. Halothane carries risk of hepatotoxicity and is no longer preferred where sevoflurane is available.
• D. Desflurane is pungent and causes coughing and breath-holding, unsuitable for mask induction.

Diffusion hypoxia occurs because nitrous oxide, being far more soluble than nitrogen, rapidly diffuses out of blood into the alveoli at the end of anaesthesia, diluting the concentrations of oxygen and carbon dioxide in the alveolar gas and causing transient hypoxia. It is prevented by administering 100% oxygen for 5-10 minutes after discontinuing nitrous oxide. Residual neuromuscular blockade and absorption atelectasis can cause hypoxia but are not specific to nitrous oxide washout, and nitrous oxide does not cause laryngospasm.

• A. This can cause hypoxia but is unrelated to nitrous oxide discontinuation specifically.
• C. Absorption atelectasis results from prolonged high FiO2, not from stopping nitrous oxide.
• D. Nitrous oxide is not pungent and does not typically cause laryngospasm.

Severe halothane hepatitis is an immune-mediated reaction in which oxidative metabolism of halothane by cytochrome P450 produces trifluoroacetyl chloride, which binds to liver proteins to form neoantigens; on re-exposure, an antibody response against these trifluoroacetylated proteins causes hepatocellular necrosis. Risk factors include repeated exposure within a short interval, middle-aged obese women, and genetic susceptibility. This immune mechanism explains the delayed onset, fever, and eosinophilia seen clinically, distinguishing it from simple dose-dependent toxicity.

• A. Mild halothane-associated transaminase elevation is dose-related, but the severe hepatitis described is immune-mediated.
• B. This mechanism describes valproate or Reye syndrome, not halothane hepatitis.
• D. Halothane hepatitis is hepatocellular, not primarily cholestatic.

The second gas effect occurs because nitrous oxide is taken up from the alveoli into blood in very large volumes, which concentrates the remaining gases in the alveoli, including the second anaesthetic agent and oxygen, and also augments tracheal inflow to replace the lost volume. This effectively increases the rate of rise of alveolar concentration and uptake of the second gas, speeding its onset of action. It is a physical gas-volume phenomenon, not related to metabolism, protein binding, or cardiac output changes.

• A. Sevoflurane undergoes minimal hepatic metabolism and this is not the mechanism of the second gas effect.
• C. The second gas effect is due to alveolar gas concentration changes, not cardiac output.
• D. Inhalational agents do not rely on plasma protein binding for this effect.

Desflurane has a pungent, irritant odour that stimulates airway reflexes, commonly causing coughing, breath-holding, laryngospasm, and increased secretions when used for mask induction, particularly at the higher concentrations needed because of its low potency. For this reason, desflurane is not used for induction of anaesthesia and is instead used for maintenance after induction with an intravenous agent or a non-irritant volatile agent such as sevoflurane. It has a low blood:gas coefficient contributing to its rapid onset and recovery, and it undergoes minimal hepatic metabolism, so fluoride toxicity is not a concern.

• A. Desflurane has low potency, requiring relatively high alveolar concentrations, not low ones.
• C. Desflurane actually has a low blood:gas coefficient, giving rapid rather than slow equilibration.
• D. Desflurane undergoes minimal metabolism and does not produce clinically significant fluoride levels.

Thiopentone, a barbiturate, induces hepatic delta-aminolevulinic acid synthase (ALA synthase), the rate-limiting enzyme of heme synthesis, which can precipitate a life-threatening acute attack in patients with acute intermittent porphyria and other hepatic porphyrias. This patient's history and positive urinary porphobilinogen during an acute attack confirm the diagnosis. Propofol, ketamine, and etomidate are considered safe alternatives for induction in porphyric patients. Avoiding barbiturates is a key safety principle taught for perioperative management of porphyria.

• A. Propofol is regarded as a safe induction agent in porphyric patients.
• B. Etomidate is not known to precipitate porphyric attacks and is used safely in such patients.
• C. Ketamine does not induce ALA synthase and is considered safe in porphyria.

Propofol is formulated as an emulsion in soybean oil, glycerol, and egg lecithin, and pain on injection results from the free (aqueous-phase) propofol activating pain receptors and the kallikrein-kinin cascade in the venous wall, especially when injected into small peripheral veins. This pain is more common with small hand veins and less with larger antecubital veins. Pretreatment with intravenous lidocaine or mixing lidocaine with propofol reduces this discomfort. The lipid emulsion itself also predisposes to bacterial contamination and hypertriglyceridaemia with prolonged infusions, but these are separate issues from injection pain.

• A. Propofol is not directly neurotoxic to peripheral nerves at clinical concentrations.
• C. Propofol does not crystallise in the emulsion form used clinically.
• D. True IgE-mediated histamine release causing injection pain is not the established mechanism; mild histamine release can occur but is not the primary cause of pain.

Ketamine is an NMDA receptor antagonist that produces dissociative anaesthesia and, unlike most other induction agents, stimulates the sympathetic nervous system causing increases in heart rate, blood pressure, and cardiac output, making it the preferred choice for induction in hypovolemic or hemodynamically unstable trauma patients. Thiopentone and propofol act on GABA-A receptors and cause significant myocardial depression and vasodilation, which can precipitate cardiovascular collapse in a hypotensive patient. Etomidate, though GABA-A mediated and relatively cardiostable, is not first-line here because ketamine's sympathomimetic action is particularly advantageous in hypotensive shock.

• A. Propofol causes significant hypotension due to vasodilation and negative inotropy, which is dangerous in this patient.
• B. Etomidate acts on GABA-A receptors, not the mechanism being tested, and while cardiostable it lacks ketamine's sympathomimetic benefit in shock.
• C. Thiopentone causes myocardial depression and vasodilation, worsening hypotension in a shocked patient.

Etomidate reversibly inhibits 11-beta-hydroxylase, an enzyme necessary for the conversion of 11-deoxycortisol to cortisol in the adrenal cortex, leading to dose-dependent adrenocortical suppression that can last 24-48 hours even after a single induction dose. This is of particular concern in critically ill or septic patients, where relative adrenal insufficiency can worsen hemodynamic instability, and is why etomidate use for maintenance infusion or repeated dosing is avoided. Despite excellent hemodynamic stability on induction, this adrenal suppression is etomidate's most clinically significant adverse effect. Thiopentone, propofol, and ketamine do not inhibit adrenal steroidogenesis.

• B. Ketamine does not inhibit 21-hydroxylase or cause adrenocortical suppression.
• C. Thiopentone does not inhibit aromatase or cause adrenal suppression; this is not its recognised mechanism of adverse effect.
• D. Propofol does not inhibit 17-alpha-hydroxylase or suppress adrenal steroidogenesis.

Ketamine is relatively contraindicated in patients with raised intracranial pressure because it increases cerebral blood flow and cerebral metabolic rate, which can worsen intracranial hypertension, particularly relevant given this patient's subdural hematoma with midline shift. It is also contraindicated in patients with schizophrenia or other psychiatric illness because it can precipitate emergence delirium, hallucinations, and exacerbation of psychotic symptoms through NMDA receptor antagonism. Thiopentone, etomidate, and propofol all reduce cerebral metabolic rate and intracranial pressure, making them preferable choices in neurosurgical patients. This combination of raised ICP and psychiatric illness makes ketamine doubly unsuitable here.

• A. Etomidate reduces ICP and does not worsen psychiatric symptoms, making it a safer choice.
• B. Propofol reduces ICP and cerebral metabolic rate and is not linked to psychotic exacerbation.
• D. Thiopentone reduces cerebral metabolic rate and ICP and is not associated with psychotic exacerbation, making it suitable here.

Propofol has a short context-sensitive half-life due to rapid hepatic metabolism and extensive redistribution, resulting in a clear-headed, rapid recovery with minimal residual sedation, hangover effect, or postoperative nausea, making it the agent of choice for day-care and ambulatory anaesthesia. Thiopentone has a long context-sensitive half-life with repeated dosing and causes a hangover effect due to slow redistribution from fat stores, making it unsuitable for quick discharge. Ketamine causes emergence delirium and prolonged psychomimetic effects, delaying safe discharge. Etomidate, though rapid acting, is not preferred for routine day-care cases due to adrenal suppression and high incidence of postoperative nausea and vomiting.

• B. Etomidate causes adrenal suppression and significant postoperative nausea and vomiting, making it unsuitable for routine day-care use.
• C. Ketamine causes emergence delirium and hallucinations, delaying safe same-day discharge.
• D. Thiopentone causes a prolonged hangover effect due to accumulation in fat and slow redistribution, delaying recovery.

Fentanyl is a synthetic opioid that is approximately 80-100 times more potent than morphine by weight and has a rapid onset of action within 1-2 minutes due to its high lipid solubility, which allows swift penetration of the blood-brain barrier, making it widely used for intraoperative analgesia and in cardiac anaesthesia where hemodynamic stability is desired. Morphine, in contrast, has a slower onset of 15-30 minutes due to lower lipid solubility and is less potent per milligram. Pethidine is roughly one-tenth as potent as morphine, and codeine is a weak opioid used mainly for mild to moderate pain and antitussive effect, both far less potent than fentanyl.

• B. Pethidine is less potent than morphine, not 100 times more potent.
• C. Codeine is a weak opioid, considerably less potent than morphine, not matching the potency described.
• D. Morphine has a slower onset of action and is far less potent per milligram compared to the agent described.

This patient has the classic opioid toxicity triad of respiratory depression, miosis, and decreased consciousness following opioid administration. Naloxone is a competitive opioid receptor antagonist that rapidly reverses opioid-induced respiratory depression and sedation, and is the specific antidote of choice. It is given intravenously in incremental doses (e.g., 0.04-0.4 mg) titrated to adequate respiration while avoiding abrupt withdrawal or loss of analgesia. Because naloxone has a shorter half-life than most opioids, repeat dosing or an infusion may be needed to prevent re-sedation.

• A. Flumazenil reverses benzodiazepine, not opioid, toxicity.
• B. Atropine treats bradycardia from vagal causes, not opioid-induced respiratory depression.
• C. Doxapram is a non-specific respiratory stimulant, not an opioid antagonist, and is not first-line here.

Tramadol is a centrally acting analgesic with a dual mechanism: it is a weak agonist at the mu-opioid receptor, and its metabolite O-desmethyltramadol also inhibits reuptake of serotonin and noradrenaline in the descending pain pathways, enhancing inhibitory pain modulation. This combination gives it efficacy in moderate pain with a lower incidence of respiratory depression compared to strong opioids. Caution is needed with concurrent serotonergic drugs because of the risk of serotonin syndrome, and tramadol lowers the seizure threshold.

• A. Pentazocine is a mixed opioid agonist-antagonist acting mainly at kappa receptors, without monoamine reuptake inhibition.
• C. Fentanyl is a potent pure mu-opioid agonist without significant monoamine reuptake inhibition.
• D. Buprenorphine is a partial mu-opioid agonist and kappa antagonist, not a monoamine reuptake inhibitor.

Succinylcholine is a depolarizing neuromuscular blocking agent structurally resembling two linked acetylcholine molecules. It binds nicotinic receptors at the motor end-plate and causes persistent depolarization rather than competitive blockade, which initially opens sodium channels and produces visible fasciculations followed by a flaccid paralysis because the end-plate becomes unresponsive to further stimulation. It is rapidly hydrolyzed by plasma pseudocholinesterase, giving it a very short duration of action, making it ideal for rapid sequence intubation when not contraindicated.

• A. Rocuronium is a non-depolarizing aminosteroid relaxant acting by competitive antagonism, not depolarization.
• B. Atracurium is a non-depolarizing benzylisoquinolinium relaxant that does not cause fasciculations.
• D. Vecuronium is a non-depolarizing aminosteroid relaxant that competitively blocks the receptor without causing fasciculations.

Malignant hyperthermia is a hypermetabolic crisis triggered in genetically susceptible individuals (ryanodine receptor RYR1 mutations) by volatile anaesthetics and succinylcholine. Excessive calcium release from the sarcoplasmic reticulum causes sustained muscle contraction, manifesting as masseter rigidity, tachycardia, rapidly rising end-tidal CO2, hyperthermia, and hyperkalemia with mixed acidosis. The temporal relation to triggering agents during anaesthesia and the combination of rigidity with hypermetabolic signs distinguishes it from other hyperthermic syndromes. Early recognition is critical because the condition is rapidly fatal without specific treatment.

• A. Thyroid storm is precipitated by stress or surgery in known or occult hyperthyroidism but does not typically present with masseter rigidity.
• C. Neuroleptic malignant syndrome occurs with antipsychotic drug use over days, not minutes after anaesthetic induction.
• D. Serotonin syndrome is linked to serotonergic drugs, not inhalational anaesthetics or succinylcholine.

Dantrolene is the specific treatment for malignant hyperthermia. It acts directly on skeletal muscle by binding the ryanodine receptor (RYR1) on the sarcoplasmic reticulum, inhibiting excessive calcium release and uncoupling excitation-contraction, thereby reducing muscle rigidity and the hypermetabolic state. It is given intravenously as a bolus and repeated until symptoms resolve, alongside stopping triggering agents, cooling measures, and correction of hyperkalemia and acidosis. Prompt dantrolene administration has markedly reduced mortality from this condition.

• A. Propranolol may be used supportively for tachyarrhythmia but does not address the underlying calcium release defect.
• B. Bromocriptine is used in neuroleptic malignant syndrome, not malignant hyperthermia.
• C. Diazepam has no specific action on the ryanodine receptor and does not treat the underlying calcium dysregulation.

Burn injury causes proliferation of extrajunctional nicotinic acetylcholine receptors across the muscle membrane beginning around the fifth day after injury. Succinylcholine depolarizes these widespread extrajunctional receptors, causing massive potassium efflux from muscle cells and can precipitate severe, even fatal, hyperkalemia and cardiac arrest. This risk persists for months after denervation injuries, burns, or prolonged immobilization, so succinylcholine is contraindicated in such patients from about day 5 after injury. Non-depolarizing agents such as rocuronium are preferred for rapid sequence induction in these situations.

• A. Cisatracurium is a non-depolarizing agent and does not carry the hyperkalemia risk associated with succinylcholine.
• B. Atracurium is a non-depolarizing agent safe in this setting with respect to hyperkalemia risk.
• D. Rocuronium is a non-depolarizing agent and does not cause the massive potassium efflux seen with succinylcholine.

Atracurium undergoes Hofmann elimination, a spontaneous, non-enzymatic degradation that occurs in plasma at physiological pH and temperature, along with ester hydrolysis by non-specific plasma esterases. Because this process is independent of hepatic or renal function, atracurium's duration of action remains predictable in patients with renal or hepatic failure, making it the preferred non-depolarizing relaxant in such settings. A breakdown product, laudanosine, can accumulate and cause CNS excitation, but this is rarely clinically significant at standard doses.

• A. Pancuronium is largely excreted unchanged by the kidneys, so its action is markedly prolonged in renal failure.
• C. Rocuronium is primarily eliminated by the liver, and its action is prolonged in hepatic impairment.
• D. Vecuronium is metabolized in the liver and excreted partly in bile and urine, with prolonged action in hepatic or renal failure.

Rocuronium, given at an intubating dose of 1.0-1.2 mg/kg intravenously, has the fastest onset among non-depolarizing neuromuscular blockers, achieving intubating conditions in about 60-90 seconds, close to that of succinylcholine. This makes it the preferred alternative for rapid sequence intubation when succinylcholine is contraindicated, such as in suspected malignant hyperthermia susceptibility, hyperkalemia risk, or pseudocholinesterase deficiency. Its action can be reversed rapidly using sugammadex if needed. Atracurium, vecuronium, and pancuronium have slower onset times and are less suitable when rapid airway control is required.

• B. Pancuronium has a slow onset of several minutes and a long duration, unsuitable for rapid sequence intubation.
• C. Vecuronium has an intermediate onset slower than rocuronium at standard intubating doses.
• D. Atracurium has a slower onset of action than rocuronium, making it less suitable for rapid sequence intubation.

Local anaesthetic systemic toxicity (LAST) is managed with standard airway and seizure control measures plus a specific antidote: 20% lipid emulsion, given as an initial bolus followed by a continuous infusion. The proposed 'lipid sink' mechanism draws lipophilic local anaesthetic molecules out of cardiac and neural tissue into the intravascular lipid phase, reducing their toxic effect, although additional mechanisms such as improved myocardial fatty acid utilization may also contribute. Current resuscitation guidelines for LAST recommend using smaller incremental doses of adrenaline (not high-dose boluses) if required, and avoiding calcium channel blockers and beta-blockers which can worsen cardiac depression. Lipid emulsion should be kept immediately available whenever large-volume peripheral nerve blocks are performed.

• A. Calcium channel blockers are avoided in LAST as they can exacerbate myocardial depression and arrhythmia.
• B. Flumazenil reverses benzodiazepines and is not indicated here since the benzodiazepine was given appropriately to control the seizure; reversing it could precipitate recurrent seizures.
• D. High-dose adrenaline is not recommended in LAST; smaller incremental doses are preferred because large doses may worsen arrhythmias and outcomes.

Bupivacaine is highly lipophilic and binds avidly to cardiac sodium channels, dissociating much more slowly from them than lidocaine during diastole ("fast-in, slow-out" kinetics). This produces profound, persistent sodium channel blockade in the myocardium, leading to refractory ventricular arrhythmias and cardiac arrest that respond poorly to standard resuscitation but may respond to intravenous lipid emulsion therapy. Lidocaine, in contrast, dissociates rapidly from sodium channels and is far less cardiotoxic at equivalent doses.

• A. Chloroprocaine is rapidly hydrolyzed by plasma cholinesterase and has a very short systemic half-life, limiting cardiotoxicity.
• B. Lidocaine has fast dissociation kinetics from cardiac sodium channels, making it far less cardiotoxic than bupivacaine.
• D. Prilocaine is associated with methaemoglobinaemia, not refractory ventricular arrhythmia.

Post-dural puncture headache results from continued leakage of CSF through the dural puncture site, reducing CSF volume and pressure. On standing, loss of the CSF cushion allows traction and stretching of pain-sensitive structures such as the meninges and bridging veins, producing a characteristic postural headache that worsens on sitting or standing and improves on lying flat. Initial management is conservative (bed rest, hydration, caffeine, simple analgesics), and an epidural blood patch is used for severe or persistent cases.

• A. Spinal needles used for subarachnoid block do not reach the spinal cord and do not cause direct cord trauma in routine lumbar puncture below L2.
• B. Cerebral vasospasm is not the established mechanism of postural post-dural puncture headache.
• D. This headache is non-infectious; fever and neck stiffness would suggest meningitis, which is not present here.

Hypotension after spinal anaesthesia results from sympathetic blockade causing venodilation, arterial vasodilation, and reduced venous return, often accompanied by bradycardia from unopposed vagal tone. First-line management is a crystalloid fluid bolus to improve preload combined with a vasopressor (phenylephrine for predominant vasoconstriction, or ephedrine when bradycardia is also present) to restore vascular tone and cardiac output. Oxygen supplementation and leg elevation are supportive measures, and the patient's airway is not compromised, so intubation is unnecessary.

• A. The patient is conscious and breathing adequately; there is no indication for intubation at this stage.
• B. Atropine may be used for symptomatic bradycardia, but it is not the first-line answer here and pacing is not indicated for sympathectomy-related hypotension.
• C. Naloxone reverses opioid effects, not the sympathetic blockade produced by local anaesthetic in the subarachnoid space, and spinal anaesthesia cannot be pharmacologically reversed.

In spinal anaesthesia, local anaesthetic is injected directly into the CSF in the subarachnoid space, so a small dose (1-3 mL) produces rapid, dense sensory and motor block within minutes. Epidural anaesthesia deposits a much larger volume of local anaesthetic into the epidural space, where it must diffuse across the dura to reach the nerve roots, giving a slower onset (15-20 minutes) and a segmental, often less dense block; a catheter can be left in the epidural space for repeated top-ups or continuous infusion, which is not standard practice for single-shot spinal anaesthesia.

• A. Epidural block is typically less dense than spinal block because the drug must diffuse through the dura before reaching the nerve roots.
• C. Catheters for continuous or repeated dosing are a hallmark of epidural technique, while spinal anaesthesia is usually a single injection.
• D. It is the epidural space, not the subarachnoid space, that requires the larger drug volume; this option reverses the comparison.

Significant coagulopathy, whether from thrombocytopenia, anticoagulant therapy, or an elevated INR, is an absolute contraindication to neuraxial anaesthesia because needle or catheter placement can cause a spinal or epidural haematoma, which may compress the cord and cause permanent neurological deficit. Other absolute contraindications include infection at the injection site, raised intracranial pressure (risk of herniation with CSF drainage), and patient refusal. Chronic kidney disease, older age, and hernia repair are not themselves contraindications to spinal anaesthesia.

• B. Inguinal hernia repair is a common and appropriate indication for spinal anaesthesia when no contraindication exists.
• C. Chronic kidney disease alone does not contraindicate neuraxial anaesthesia and is not listed among the absolute contraindications.
• D. Advanced age is not an absolute contraindication to spinal anaesthesia; many elderly patients safely receive it.

Total spinal anaesthesia occurs when an excessive dose of local anaesthetic reaches the cervical spinal cord and brainstem, typically after unintentional subarachnoid injection of an epidural dose, causing apnoea from phrenic and intercostal nerve paralysis, profound hypotension and bradycardia from complete sympathetic blockade, and loss of consciousness from brainstem hypoperfusion or direct anaesthetic spread. Management is purely supportive: secure the airway and ventilate with 100% oxygen, support the circulation with fluids and vasopressors/atropine, and maintain this support until the block recedes, since there is no specific reversal agent for local anaesthetic in the CSF.

• A. Draining CSF does not reliably remove the local anaesthetic quickly enough and is not the established emergency management; supportive care takes priority.
• C. The clinical picture is due to extensive neuraxial blockade, not anaphylaxis, so steroids are not indicated.
• D. Naloxone reverses opioid effects and has no role in reversing local anaesthetic-induced total spinal block.

Cricoid pressure, or Sellick's maneuver, involves applying firm backward pressure on the cricoid cartilage to compress the underlying oesophagus against the cervical vertebral bodies, theoretically occluding the oesophageal lumen and preventing passive regurgitation of gastric contents into the pharynx. The cricoid cartilage is chosen because it is the only complete tracheal ring, providing a rigid structure for effective compression without collapsing the airway. Its efficacy has been questioned in recent literature, as imaging studies show the oesophagus may be lateral to the cricoid rather than directly posterior, and improper application can worsen the laryngoscopic view or even obstruct the airway.

• A. The maneuver aims to prevent reflux of gastric contents, not to promote their expulsion.
• B. Cricoid pressure acts by mechanical oesophageal occlusion, not by altering sphincter tone via a vagal pathway.
• C. Cricoid pressure often worsens rather than improves the laryngoscopic view by distorting airway anatomy.

This scenario describes the 'cannot intubate, cannot ventilate' (CICV) emergency, a life-threatening situation in which standard airway rescue measures (laryngoscopy and supraglottic devices) have failed and the patient is hypoxic. According to the Difficult Airway Society and standard anaesthesia algorithms, when CICV is confirmed despite optimal attempts, the next step is to secure an emergency surgical airway via cricothyroidotomy (needle or surgical) to restore oxygenation before irreversible hypoxic injury occurs. Repeating failed techniques wastes critical time, and in an emergency caesarean under general anaesthesia, waking the patient is not feasible given ongoing hypoxia and surgical urgency.

• A. Repeating muscle relaxant without a ventilation strategy does not address the failure to ventilate and wastes time.
• B. Repeating a failed technique delays definitive airway rescue and risks further desaturation.
• C. The patient is already anaesthetised and hypoxic; waking is not a safe or timely option in this emergency.

Emergency cricothyroidotomy is indicated when oxygenation and ventilation cannot be achieved by any other means (failed intubation and failed mask ventilation) in a rapidly desaturating patient, particularly in trauma with distorted airway anatomy. It provides rapid surgical access to the airway through the cricothyroid membrane, which is relatively avascular and easily palpable, allowing airway control within seconds to a few minutes. Fiberoptic intubation is time-consuming and impractical with active bleeding obscuring the view. Blind nasal intubation is contraindicated in suspected midface/base of skull trauma, and elective tracheostomy is too slow for this immediate, life-threatening hypoxia.

• A. Tracheostomy under local anaesthesia is a planned procedure too slow to address immediate life-threatening hypoxia.
• B. Blind nasotracheal intubation risks further trauma and is contraindicated with suspected facial/skull base fractures.
• C. Fiberoptic intubation requires a clear view and time, both unavailable in active hemorrhage with critical desaturation.

This is laryngospasm, a reflex adduction of the vocal cords causing airway obstruction, commonly triggered by light anaesthesia with airway stimulation. The first step is to remove the stimulus, apply 100% oxygen, and perform jaw thrust with firm pressure at the laryngospasm notch (behind the lobule of the ear) to stimulate the vagal reflex and break the spasm. If this fails and hypoxia worsens, a small dose of propofol or succinylcholine with intubation is reserved for refractory cases. Early recognition and gentle airway manoeuvres prevent escalation to a surgical airway.

• A. Deepening anaesthesia is a second-line option after jaw thrust and oxygen have failed, not the immediate first action.
• B. Succinylcholine with intubation is reserved for cases refractory to simple airway manoeuvres, not the first step.
• D. Cricothyroidotomy is a last resort for a completely obstructed airway unresponsive to all other measures.

Pregnant patients beyond the first trimester are considered 'full stomach' due to delayed gastric emptying and reduced lower oesophageal sphincter tone from progesterone, raising the risk of Mendelson syndrome (acid aspiration pneumonitis). Rapid sequence induction with cricoid pressure and a cuffed endotracheal tube secures the airway quickly while minimizing the time the airway is unprotected and reduces passive regurgitation. Preoxygenation and avoidance of mask ventilation further reduce gastric insufflation. This is the standard of care for full-stomach emergency surgery in pregnancy.

• A. Mask induction with positive-pressure ventilation risks gastric insufflation and does not protect the airway from aspiration.
• B. Lateral position with spontaneous ventilation delays definitive airway control and does not prevent aspiration as effectively as rapid sequence induction.
• C. Awake fibreoptic intubation is reserved for anticipated difficult airways, not routinely used for aspiration prophylaxis in this setting.

This patient has multiple Apfel risk factors for PONV: female sex, history of motion sickness, non-smoking status, and use of postoperative opioids, placing her at high risk. Ondansetron, a 5-HT3 receptor antagonist, is a first-line prophylactic antiemetic and is most effective when given near the end of surgery rather than at induction, as its duration better covers the early postoperative period. Combination prophylaxis with a second agent such as dexamethasone is often added in high-risk patients. Timing and agent selection are guided by consensus PONV management guidelines.

• A. Metoclopramide has weaker antiemetic efficacy for PONV prophylaxis compared to 5-HT3 antagonists and is not the preferred first-line agent.
• B. Atropine is an antisialagogue and anticholinergic, not indicated for PONV prophylaxis in this context.
• C. Naloxone would reverse opioid analgesia and is not used for PONV prophylaxis.

Postoperative shivering results from redistribution hypothermia and a lowered thermoregulatory set-point after anaesthesia, with the hypothalamus triggering compensatory thermogenesis. Tramadol, acting on both opioid receptors and monoamine reuptake, is highly effective in abolishing shivering and is a first-line pharmacologic agent alongside clonidine. Active warming measures should be continued alongside drug therapy. Benzodiazepines and anticholinergics are not established treatments for this condition.

• B. Naloxone would reverse opioid analgesia and has no role in treating shivering; it is used for opioid overdose.
• C. Atropine has no antishivering effect and is used for bradycardia or as an antisialagogue.
• D. Midazolam has sedative properties but is not an established treatment for postoperative shivering.

Prolonged apnea after a single dose of succinylcholine, with a train-of-four pattern showing equal depression of all four twitches without fade, points to a phase I depolarizing block that has failed to terminate normally. This is characteristic of succinylcholine apnea caused by genetically atypical or quantitatively deficient plasma (pseudo)cholinesterase, which normally hydrolyzes succinylcholine rapidly. In contrast, non-depolarizing block produces fade on train-of-four stimulation. Management is supportive ventilation until the block resolves spontaneously, with later dibucaine number testing to confirm the enzyme abnormality.

• B. Malignant hyperthermia presents with hypermetabolism, hyperthermia, and muscle rigidity, not isolated prolonged apnea with this twitch pattern.
• C. No second dose of a non-depolarizing agent was given in this scenario, and such a block would show fade on train-of-four.
• D. Sevoflurane alone does not cause significant neuromuscular blockade of this magnitude or duration.

In the supine position beyond mid-pregnancy, the gravid uterus compresses the inferior vena cava and aorta against the vertebral column, reducing venous return and cardiac output, a phenomenon called aortocaval compression or supine hypotensive syndrome. Tilting the patient 15 degrees to the left, typically with a wedge under the right hip, displaces the uterus off the great vessels and restores venous return. This is a standard positioning requirement for all pregnant women undergoing surgery in the supine position beyond the second trimester. Fluid preloading is adjunctive but does not address the mechanical cause.

• B. An abdominal binder would worsen, not relieve, compression on the great vessels.
• C. Head-down tilt does not relieve uterine compression on the vena cava and aorta.
• D. A fluid bolus is adjunctive therapy but does not correct the underlying mechanical vena caval compression.

Ketamine is a sympathomimetic agent that stimulates catecholamine release and increases heart rate and blood pressure, making it unsuitable for induction or maintenance of anaesthesia in pheochromocytoma, where exaggerated catecholamine surges can precipitate a hypertensive crisis during tumour handling. Preferred agents include propofol for induction, along with opioids for analgesia and agents that avoid histamine release or sympathetic stimulation for muscle relaxation. Adequate alpha- and beta-blockade preoperatively, invasive blood pressure monitoring, and availability of short-acting vasodilators and vasopressors are essential throughout the perioperative period.

• A. Fentanyl is commonly used safely for analgesia in these patients without significant catecholamine release.
• C. Atracurium causes minimal sympathetic stimulation and is considered a safe muscle relaxant choice in this setting.
• D. Propofol is a preferred induction agent in pheochromocytoma due to its favourable haemodynamic profile.

Pregnancy reduces functional residual capacity (FRC) by 20-30% due to the elevated diaphragm, while oxygen consumption rises by about 20% to meet fetal and maternal metabolic demands. This combination shrinks the oxygen reserve available during apnoea, so desaturation occurs much faster than in non-pregnant patients once ventilation stops. This is why obstetric general anaesthesia mandates careful preoxygenation and is associated with a higher incidence of difficult or failed intubation and rapid hypoxaemia. Airway oedema and engorgement from fluid retention and capillary changes further compound difficult laryngoscopy.

• A. Systemic vascular resistance decreases in pregnancy and is unrelated to oxygen reserve during apnoea.
• C. Minute ventilation is increased, not decreased, in pregnancy due to progesterone-driven hyperventilation.
• D. Plasma cholinesterase activity is actually decreased in pregnancy, prolonging succinylcholine action, and this does not affect oxygen reserve.

The WHO analgesic ladder recommends a stepwise approach: Step 1 uses a non-opioid (paracetamol or NSAID) with or without an adjuvant for mild pain; Step 2 adds a weak opioid (codeine, tramadol) for mild-to-moderate pain that persists or worsens; and Step 3 uses a strong opioid (morphine) for moderate-to-severe pain. This patient's pain has escalated from the non-opioid step but is still moderate, so the correct next step is to add a weak opioid to the existing non-opioid rather than jumping straight to a strong opioid. The non-opioid should be continued, not stopped, because of the synergistic analgesic effect and opioid-sparing benefit.

• B. Paracetamol should be continued as a background analgesic even when opioids are added, not discontinued.
• C. Combining two non-opioids (e.g., paracetamol and NSAID) is not part of the ladder's progression for worsening pain and provides limited additional benefit.
• D. Skipping to a strong opioid is not the standard WHO stepwise approach for moderate pain that has just progressed from step 1.