ANZCA Final Exam key terms

The alveolar concentration of an inhaled anaesthetic at one atmosphere that prevents purposeful movement in 50% of patients in response to a standard surgical stimulus. It allows comparison of potency between volatile agents.

The alveolar concentration of an inhaled anaesthetic at which 50% of patients respond purposefully to command. It is typically about one-third of MAC and guides emergence and sedation dosing.

The time for plasma concentration of a drug to fall by half after stopping an infusion, measured from the moment of cessation. It lengthens with infusion duration for lipophilic drugs such as propofol and remifentanil differs little.

The modelled drug concentration at the site of action (usually brain) that produces the clinical effect. It lags behind plasma concentration, explaining hysteresis between dose and observed response during target-controlled infusion.

The phenomenon where the measured effect of a drug differs at the same plasma concentration depending on whether concentration is rising or falling. It reflects delay between plasma and effect-site equilibration.

The accelerated rise in alveolar concentration of a carrier gas caused by rapid uptake of a concurrently administered high-volume gas such as nitrous oxide. It speeds induction with volatile agents.

The observation that a higher inspired concentration of an inhaled anaesthetic raises its alveolar concentration proportionally faster, because a greater fraction of delivered gas is taken up, concentrating remaining gas.

A transient fall in alveolar oxygen tension after ceasing nitrous oxide, as the large volume of nitrous oxide diffusing from blood into alveoli dilutes oxygen. Prevented by giving high-flow oxygen at emergence.

Situations where nitrous oxide should be avoided: pneumothorax, bowel obstruction, middle-ear or vitreoretinal surgery, gas embolism risk, and severe pulmonary hypertension. It diffuses into closed gas spaces faster than nitrogen leaves.

Prolonged paralysis after suxamethonium due to inherited deficiency of plasma butyrylcholinesterase or an atypical enzyme variant. Managed with continued ventilation and sedation until neuromuscular function recovers, which may take hours.

Depolarising neuromuscular block characteristic of suxamethonium, with reduced twitch height, no fade, and no post-tetanic potentiation. It reflects persistent depolarisation rather than competitive receptor antagonism.

The ratio of the fourth to the first evoked twitch in response to four supramaximal stimuli. A ratio above 0.9 indicates adequate recovery from non-depolarising neuromuscular blockade.

A modified gamma-cyclodextrin that encapsulates rocuronium and vecuronium, reversing even deep neuromuscular blockade within minutes. It has no effect on suxamethonium or benzylisoquinolinium agents.

A pharmacogenetic hypermetabolic crisis triggered by volatile anaesthetics or suxamethonium in susceptible individuals, causing rigidity, hyperthermia, acidosis and hyperkalaemia. Treated by stopping triggers, cooling, and dantrolene.

A muscle relaxant that inhibits calcium release from the sarcoplasmic reticulum and is the specific antidote for malignant hyperthermia. Given as 2.5 mg/kg intravenously and repeated until the crisis abates.

Reflex closure of the vocal cords due to stimulation of the laryngeal nerves, commonly during light anaesthesia or airway irritation. Managed with cessation of stimulus, positive pressure, deepening anaesthesia and, if needed, suxamethonium.

A structured sequence of planned steps for managing unexpected difficulty with ventilation, supraglottic device placement, laryngoscopy or intubation. It emphasises limiting attempts, calling for help, and maintaining oxygenation throughout.

A life-threatening situation where neither tracheal intubation nor any other means of oxygenation succeeds. It mandates immediate emergency front-of-neck airway access, usually a scalpel-bougie-tube technique.

An intubation technique for patients at risk of aspiration, using preoxygenation, a rapid-onset induction agent and neuromuscular blocker, minimal positive pressure, and immediate intubation with cricoid pressure often applied.

Chemical injury to the lungs from inhaling acidic gastric contents, causing bronchospasm, hypoxaemia and pulmonary oedema within hours. Management is supportive, with airway suction, oxygen and lung-protective ventilation.

Nausea or vomiting occurring within 24 hours of surgery, driven by patient, surgical and anaesthetic risk factors. Prophylaxis uses multimodal antiemetics targeting different receptors, with rescue treatment for breakthrough symptoms.

A validated risk score for postoperative nausea and vomiting using four predictors: female sex, non-smoking status, history of motion sickness or vomiting, and use of postoperative opioids. Each adds roughly 20% risk.

Anaesthesia maintained by continuous intravenous drug infusion, usually propofol with an opioid, without inhaled agents. It avoids volatile exposure and is useful for malignant hyperthermia susceptibility or severe postoperative nausea.

Administration of high inspired oxygen before induction to replace alveolar nitrogen with oxygen, creating a reservoir that prolongs safe apnoea time. Achieved with a tight-fitting mask and adequate flow for several minutes.

Pain caused by a lesion or disease of the somatosensory nervous system, often described as burning, shooting or electric-shock like, with allodynia or hyperalgesia. It responds poorly to simple analgesics and requires agents such as gabapentinoids or tricyclics.

Increased responsiveness of nociceptive neurons in the central nervous system to normal or subthreshold input, amplifying pain. It underlies hyperalgesia and allodynia and is a target for pre-emptive and multimodal analgesia.

The use of two or more analgesic agents or techniques with different mechanisms to improve pain relief while reducing individual drug doses and side effects. Common components include paracetamol, NSAIDs, local anaesthetics and opioids.

The reduction in opioid dose required to achieve equivalent analgesia when another analgesic is co-administered. It lowers opioid-related adverse effects such as sedation, respiratory depression and ileus.

A reduced analgesic response to an opioid after repeated exposure, requiring higher doses for the same effect. It develops over days to weeks and is distinct from dependence and addiction.

A paradoxical increase in pain sensitivity caused by opioid exposure, distinct from tolerance. It may present as diffuse pain worsening with dose escalation and is managed by reducing or rotating opioids.

A system allowing patients to self-administer small intravenous opioid boluses with a lockout interval. It provides individualised analgesia and high satisfaction, with monitoring required for sedation and respiratory depression.

A regional anaesthetic technique depositing local anaesthetic between the internal oblique and transversus abdominis muscles to block abdominal wall nerves. It provides somatic analgesia after abdominal surgery but not visceral pain.

Adverse effects from excessive local anaesthetic in the circulation, causing perioral tingling, tinnitus, seizures, arrhythmias and cardiovascular collapse. Treated with airway support and intravenous lipid emulsion.

A chronic pain condition after injury, with disproportionate pain, swelling, skin colour and temperature change, and motor or sensory disturbance. Management is multidisciplinary, emphasising early mobilisation and pain modulation.

Myocardial infarction occurring during or after surgery, often silent and detected by troponin rise plus ischaemic features. It is usually driven by supply-demand imbalance rather than plaque rupture and carries high mortality.

A tool estimating major cardiac complications after non-cardiac surgery using six factors: high-risk surgery, ischaemic heart disease, heart failure, cerebrovascular disease, diabetes on insulin, and renal impairment. Each factor increases risk.

A non-invasive test measuring gas exchange during graded exercise to assess functional capacity and cardiorespiratory reserve. Anaerobic threshold and peak oxygen uptake help stratify perioperative risk before major surgery.

Interventions before surgery, such as exercise, nutrition and psychological support, aimed at improving functional reserve and reducing postoperative complications. It is most useful in frail or high-risk patients undergoing major surgery.

A multidisciplinary care pathway using evidence-based elements such as carbohydrate loading, opioid-sparing analgesia, early feeding and mobilisation to reduce surgical stress and shorten hospital stay.

Use of beta-blockers around surgery to reduce myocardial oxygen demand. Continuation is recommended in patients already taking them, but starting acutely to prevent complications is generally discouraged due to stroke and hypotension risk.