Prolonged mivacurium-induced neuromuscular blockade in patients with reduced plasma cholinesterase activity

Mivacurium is a recently released short-acting nondepolarizing muscle relaxant, metabolized by plasma cholinesterase. The short duration of action makes mivacurium an increasingly popular choice for muscle relaxation in ambulatory surgery procedures. Individuals with abnormalities of plasma cholinesterase, however, may have longer than expected duration of action of mivacurium, requiring prolonged mechanical ventilation. We present two cases where this occurred.