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Myasthenia Gravis Anaesthesia — FRCA Final MCQ

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HardGeneral AnaesthesiaMyasthenia Gravis AnaesthesiaFRCA Final

A 40-year-old woman with stable Osserman class IIb myasthenia gravis, treated with pyridostigmine 60 mg four times daily and prednisolone 10 mg daily, undergoes thymectomy. Her trachea has been intubated without a neuromuscular blocking drug, but adequate surgical conditions cannot be achieved without neuromuscular blockade. Renal function is normal, and quantitative neuromuscular monitoring and sugammadex are available. Which is the most appropriate initial strategy?

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Correct answer: B — Rocuronium 0.06 mg/kg in monitored increments

The correct answer is B. Reduced functional postsynaptic nicotinic acetylcholine receptor density makes patients with myasthenia gravis profoundly and variably sensitive to non-depolarising neuromuscular blockers. When blockade is essential, rocuronium should be given in increments of approximately one-tenth its standard 0.6 mg/kg intubating dose, guided by quantitative monitoring. It is preferred because residual blockade can be reversed directly with sugammadex. Suxamethonium resistance occurs, but pyridostigmine may inhibit its metabolism and prolong its effect, making the response unpredictable. Standard atracurium or cisatracurium doses risk severe prolonged paralysis and cannot be reversed with sugammadex. Avoiding neuromuscular blockers is preferable when feasible, but inadequate surgical conditions make that strategy inappropriate here.

Reference: Daum P, Smelt J, Ibrahim IR. Perioperative management of myasthenia gravis — section: Suxamethonium and non-depolarising neuromuscular blocking drugs. BJA Education 2021;21(11):414-419. https://pubmed.ncbi.nlm.nih.gov/34707886/