Malignant Hyperthermia Crisis

About this case

A healthy 24-year-old presents for shoulder arthroscopy and deteriorates mid-case. The scenario begins as a routine anaesthetic and becomes a crisis, so the examiner is watching when you recognise it rather than only what you do afterwards. Masseter rigidity at induction is available early, and a rising end-tidal CO₂ precedes the temperature change.

Key clinical features

• Rising Temperature

  39.8°C — late but specific sign of MH

• ETCO₂ 78

  Unexplained rise despite ↑ minute ventilation

• Masseter Rigidity

  Noted at induction — early warning sign

• Tachycardia + Arrhythmia

  HR 142, PVCs — hyperkalemia from rhabdo

What the examiner is testing

• Whether you recognise malignant hyperthermia from a rising ETCO₂ that does not respond to increased minute ventilation, rather than waiting for the late temperature rise.
• How you construct a differential for unexplained hypercarbia and tachycardia before committing to an MH diagnosis.
• Your ability to run a crisis and communicate with the surgical team simultaneously, which the examiner probes by interrupting.
• How you handle the downstream consequences — arrhythmia and hyperkalaemia from rhabdomyolysis — rather than treating the trigger alone.

Where candidates lose points

• Anchoring on a simpler explanation (light anaesthesia, hypoventilation) and defending it after the ETCO₂ trend has made it untenable.
• Describing treatment competently but never stating the diagnosis out loud — examiners score the recognition, not just the plan.
• Neglecting disposition and family counselling once the acute crisis is stabilised.

How it is scored

Every BoardSim case is scored across the same five phases — pre-operative evaluation, anaesthetic plan, intra-operative management, crisis management, and emergence — for a total of 100 points, with a pass set at 70 and no missed critical action. You receive a written report against each phase rather than a single number. Read the scoring methodology.