Unexpected prolonged neuromuscular block after mivacurium: a case report

To present a case of unexpected prolonged apnoea following the administration of mivacurium, a short-acting muscle relaxant and to identify the factors for early diagnosis and management.

A 19-year-old physically fit lady without personal or family history suggestive of anaesthetic problems had an excision of fibro-adenoma from the breast. She did not recover as quickly as was expected from the anaesthetic, which included the administration of mivacurium. She had prolonged neuromuscular blockade. She was kept ventilated and sedated. Five hours after the last dose of mivacurium, she showed signs of spontaneous respiration and at 6 h she was extubated and fully recovered. It was shown later that the patient had a pseudocholinesterase deficiency.

Pseudocholinesterase deficiency is an uncommon occurrence but should be highly suspected in cases of prolonged paralysis following the administration of a short-acting muscle relaxant. The use of a nerve stimulator is recommended whenever muscle relaxants are used. Muscle relaxants should be used only when facilities for prolonged ventilation are available.