Anesthesia
The anesthesia component tests preoperative assessment, airway prediction, drug selection, and recognition of two exam favourites: malignant hyperthermia and local anaesthetic systemic toxicity.
Preoperative assessment
- ASA physical status I–VI: I is healthy, III is severe systemic disease, IV is a constant threat to life, V is moribund and VI is a brain-dead organ donor. Add the suffix E for emergency surgery.
- Airway predictors: Mallampati III–IV, thyromental distance <6 cm, mouth opening <3 cm, short thick neck, limited cervical extension.
- Fasting: 2 h for clear fluids, 4 h for breast milk, 6 h for a light meal.
Drugs
- Induction: propofol, ketamine (useful in shock because it preserves haemodynamics), etomidate.
- Suxamethonium is a depolarising blocker with rapid onset and offset. It is contraindicated in hyperkalaemia, burns older than 24–48 h, spinal cord injury, denervation and malignant hyperthermia susceptibility. Use rocuronium, reversible with sugammadex, instead.
Crises
- Malignant hyperthermia: rising end-tidal CO2, masseter spasm, hyperthermia and acidosis. Stop volatile agents and suxamethonium, hyperventilate with 100% oxygen, and give dantrolene 2.5 mg/kg IV.
- Local anaesthetic systemic toxicity: 20% lipid emulsion 1.5 mL/kg bolus followed by an infusion.
Worked example
A 28-year-old with appendicitis has a full stomach. A rapid sequence induction with preoxygenation, an induction agent, cricoid pressure and suxamethonium is chosen because the priority is a secure airway with minimal aspiration risk.
Traps
Skipping preoxygenation, giving suxamethonium to a burned or spinal-injured patient, and misreading early malignant hyperthermia as sepsis waste easy marks.