ANZCA Primary flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

MAC definition

The minimum alveolar concentration at which 50% of patients do not move in response to a standardised surgical stimulus; a measure of volatile anaesthetic potency.

Oxygen delivery equation

DO2 equals cardiac output multiplied by arterial oxygen content, where CaO2 is (1.34 × haemoglobin × saturation) plus (0.003 × PaO2).

MAC-awake

The alveolar concentration at which 50% of patients respond appropriately to command; approximately one-third of the MAC value for that agent.

Train-of-four ratio

Ratio of the fourth to the first evoked twitch in a train of four; a ratio above 0.9 indicates adequate recovery from neuromuscular blockade.

Phase I block

Depolarising block produced by suxamethonium, characterised by fasciculations, absence of fade on train-of-four, and potentiation by anticholinesterases.

Lipid emulsion therapy

Specific rescue treatment for local anaesthetic systemic toxicity, given as a bolus followed by infusion, in addition to airway and circulatory support.

Frank-Starling relationship

Stroke volume increases with increasing ventricular end-diastolic volume up to a plateau; increased contractility shifts the whole relationship upward.

Critical oxygen delivery

The delivery threshold, roughly 300-330 mL/min in adults, below which oxygen consumption becomes supply-dependent and anaerobic metabolism develops.

Gate control theory

Large-diameter Aβ afferent input inhibits dorsal horn transmission of small-fibre nociceptive signals through inhibitory interneurons, reducing perceived pain.

Central sensitisation

Activity-dependent increase in dorsal horn neuronal excitability, mediated largely by NMDA receptor activation, producing wind-up and hyperalgesia.

Mu opioid receptor effects

G-protein coupled receptor mediating analgesia, respiratory depression, miosis, euphoria, constipation, and physical dependence; the target of morphine and fentanyl.

Equianalgesic opioid conversion

Oral morphine 30 mg is approximately equivalent to oral oxycodone 20 mg; reduce the calculated dose by 25-50% for incomplete cross-tolerance.

Neuropathic pain features

Pain described as burning, shooting, or electric-shock like, often with allodynia; responds to gabapentinoids, tricyclics, and SNRIs.

Multimodal analgesia

Combining analgesic agents acting at different sites and mechanisms to improve pain relief while reducing dose-related adverse effects of any single drug.

NSAID mechanism

Inhibition of cyclo-oxygenase reduces prostaglandin synthesis, giving analgesic and anti-inflammatory effects with risks of gastric, renal, and platelet toxicity.

Nociceptor fibre types

A-delta fibres are myelinated and conduct sharp, fast pain; unmyelinated C fibres conduct slow, burning pain.

Revised cardiac risk index

Six predictors of perioperative cardiac events: ischaemic heart disease, heart failure, cerebrovascular disease, insulin-treated diabetes, renal impairment, and high-risk surgery.

Apfel PONV score

Four equally weighted predictors: female sex, non-smoker status, history of PONV or motion sickness, and postoperative opioid use.

Perioperative glycaemic target

Blood glucose is typically targeted at approximately 6-10 mmol/L perioperatively, as hyperglycaemia is associated with infection and increased mortality.

Clear fluid fasting interval

Clear fluids are typically permitted until two hours before anaesthesia, reflecting normal gastric emptying rather than a fixed midnight fasting cut-off.

Perioperative beta-blocker rule

Patients already established on beta-blockers should generally continue them perioperatively; abrupt withdrawal risks rebound tachycardia and myocardial ischaemia.

Perioperative anaphylaxis triggers

Common causes include neuromuscular blocking agents, antibiotics, chlorhexidine, and latex; serial serum tryptase sampling supports later confirmation.

Enhanced recovery principles

A bundle including preoperative optimisation, carbohydrate loading, opioid-sparing analgesia, early mobilisation, and early enteral feeding to speed functional recovery.

VTE risk stratification

Venous thromboembolism prophylaxis is chosen by procedure and patient risk, using mechanical methods and pharmacological agents when bleeding risk allows.

Henderson-Hasselbalch equation

pH equals 6.1 plus the log of bicarbonate divided by 0.03 times PaCO2; an acute 10 mmHg rise in PaCO2 lowers pH by about 0.08.

Bohr effect

A rightward shift of the oxygen-haemoglobin dissociation curve, reducing affinity, caused by raised CO2, hydrogen ion, temperature, and 2,3-DPG.

Nernst equation

Equilibrium potential equals RT/zF multiplied by the natural log of the ratio of outside to inside ion concentration; potassium dominates resting membrane potential.

Starling equation

Fluid flux equals the filtration coefficient times the difference between net hydrostatic and oncotic gradients across the capillary membrane.

Functional residual capacity

The volume remaining in the lungs after passive expiration, equal to expiratory reserve volume plus residual volume; reduced by supine posture, obesity, pregnancy, and anaesthesia.

Clearance and half-life

Clearance is the rate of elimination divided by plasma concentration; half-life equals 0.693 multiplied by volume of distribution divided by clearance.

Anion gap formula

Sodium minus the sum of chloride and bicarbonate, normally 8-12 mmol/L; a raised gap indicates accumulation of unmeasured anions such as lactate or ketones.

Graham's law of diffusion

The diffusion rate of a gas is inversely proportional to the square root of its molecular weight, explaining rapid nitrous oxide uptake and elimination.