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OSCE: actor and procedure stations · Core08 / 22

Family history of malignant hyperthermia before hernia repairActor: a 24-year-old man booked for elective day-case inguinal hernia repair

Actor: counselling a frightened patient about inherited anaesthetic risk

From memory: the diagnosis and the notes are hidden. Answer each question aloud, then press Show.

Know this first

  • MH: mainly autosomal dominant, variable penetrance (about 40% in one RYR1 cohort).
  • Triggers: all potent volatile agents and suxamethonium.
  • Safe: TIVA, nitrous oxide, local or regional; regional may be preferred.
  • Machine: flush to under 5 ppm or fit charcoal filters; keep fresh gas flow 10 L/min or more.
  • Dantrolene within 10 minutes of the first sign.

The patient

Actor: a 24-year-old man booked for elective day-case inguinal hernia repair. His uncle died during an anaesthetic years ago; the family was told it was malignant hyperthermia. He is frightened and talking about cancelling. Task: counsel him and explain the plan.

The examiner asks

Answer aloud, then press Show.

  1. Open

    How do you start?

    Show the answerHide the answer
    • I'm seeing a young man before hernia repair whose uncle died under anaesthesia, possibly from MH. Patient
    • Tell me what you know about what happened to your uncle, and when. Communication
    • Has anyone else in the family had anaesthetic problems, or been tested?

  2. Explain

    Explain the condition and your plan.

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    • MH is an inherited muscle reaction to some anaesthetic gases and one muscle relaxant. (Communication)
    • It runs in families, passed from one parent, but not everyone who carries it reacts.
    • Until tested, we'll treat you as at risk. That's the safe default.
    • You can have this operation safely, because we'll avoid every trigger.
    • I'd suggest a spinal or nerve block, or a drip anaesthetic with no gases.

  3. Respond

    He asks: 'Am I going to die like my uncle?'

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    • I understand why you're scared. What happened to your uncle was terrible. (Communication)
    • The difference is that we know about the risk, so no trigger drugs will be used.
    • The machine will be flushed clean of gas, and the antidote kept in theatre.
    • If anything unexpected happened, dantrolene would be given within minutes.

  4. Respond

    He asks: 'What about my children?'

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    • They could have inherited it, so they should also be treated as at risk. (Communication)
    • Testing is a muscle biopsy at a specialist centre, or a gene test if the family mutation is known.
    • If a mutation is found in you, relatives with it count as susceptible without a biopsy.

  5. Close

    How do you close?

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    • I'll refer you to an MH testing centre after this operation. Communication
    • Until then, tell every doctor and dentist, and carry an alert card.
    • Today: no triggers, a flushed machine, and close temperature and carbon dioxide monitoring.
    • I flag MH susceptibility in his notes and brief the theatre team before the list. After surgery

Fatal mistakes

  • Planning volatile agents or suxamethonium.
  • Reassurance without a plan.
  • No referral for testing.

Checked against: Miller 10e · Barash 9e

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