Muscle hypertonus after intravenous suxamethonium: A clinical problem.

Hypertonus of masseter and chest wall muscle in one patient following intravenous suxamethonium is reported. Subsequent investigations including electromyography and muscle biopsy with in vitro pharmacological testing failed to reveal any abnormality to account for the response. The clinical problems presented to the anaesthetist when suxamethonium-induced hypertonus occurs are discussed. The relationship between a hypertonic reaction to suxamethonium and neuromuscular disease (including myotonic disorders and the malignant hyperpyrexia myopathy) is considered.