Prolonged paralysis following mivacurium administration

Mivacurium is a benzylisoquinolone, choline-like, non-depolarizing muscle relaxant. Its onset of action is similar to that of atracurium but its duration of action is shorter (approximately 10-15 minutes). Mivacurium is metabolized by plasma cholinesterases at approximately 70% of the rate of metabolism of suxamethonium 1 . Deficiency or abnormality of plasma cholinesterase may cause the duration of action of both suxamethonium 2,3 and mivacurium 2,4,5,6 to be greatly prolonged. We describe a case of prolonged mivacurium paralysis after day surgery. Laboratory investigations showed a genetic tendency toward abnormal cholinesterase levels, but markedly depressed cholinesterase activity was suggestive of additional acquired causes. This patient had a history of liver disease, malnutrition and anticholinesterase use, which we believe were the most significant factors involved.