Prolonged neuromuscular block associated with mivacurium.

Mivacurium is a relatively new short-acting nondepolarizing neuromuscular blocker. A recommended dose of 0.15-0.2 mg kg-1 provides tracheal intubating conditions within 2.5 min and duration of action of 15-30 min, making it a possible alternative to suxamethonium for short procedures requiring tracheal intubation. However, in common with suxamethonium its metabolism depends primarily on plasma cholinesterase and its duration of action is prolonged in patients with reduced plasma cholinesterase activity. We present a case of unexpected prolonged neuromuscular block in a child with previously undiagnosed plasma cholinesterase deficiency.