Postoperative apnoea and latent myasthenia gravis

Abstract

Sum in a r yWe report a case of alcuronium induced postoperative apnoea due to latent myasthenia gravis in a patient with no other clinical man festations of the disease at presentation. Acetylcholine receptor antibody estimation was used to confirm the diagnosis. Key wordsComplication; myasthenia gravis. Neuromuscular relaxants; alcuronium.Myasthenia gravis is a recognised but rare cause of prolonged apnoea and is due to a failure to reverse neuromuscular blockade. Some cases are mild or intermittent and standard diagnostic tests may be unrevealing. We describe a patient in whom the apnoea was precipitated by the administration of alcuronium, where acetylcholine receptor antibody assay helped to confirm the diagnosis. Case historyThe patient was a 69-year-old lady who presented after a routine cataract extraction. Preoperative history and examination were unremarkable and, following premedication with promethazine 25 mg, metoclopramide 5 mg and atropine 0.6 mg, anaesthesia was induced with thiopentone 250 mg and maintained with nitrous oxide 60% in oxygen, and fentanyl 100 pg. Muscle relaxation was achieved using alcuronium 20 mg. Reversal of neuromuscular blockade was attempted after 75 minutes of uneventful surgery with neostigmine 2.5 mg and atropine 1.2 mg with no effect. Muscle power and respiratory effort remained absent despite further doses of neostigmine and atropine. During this period peripheral nerve stimulation demonstrated fade to both a train of four, supramaxima1 single stimuli and tetanic stimulation at 50 Hz and also showed post-tetanic facilitation.The patient was subsequently transferred to the intensive care unit for artificial ventilation. On admission she was rousable, but was unable to move her limbs and could make no appreciable respiratory effort. She was sedated with an Althesin infusion. Her clinical course during ventilator therapy was marked by a myocardial infarction associated with transient hypotension, but no complications followed this. After 15 hours she regained skeletal muscle power and sufficient respiratory effort to have a vital