Interactions between mivacurium, rocuronium, and vecuronium during general anesthesia

This study was designed to examine the interactions between mivacurium and rocuronium or vecuronium when administered during a standardized anesthetic technique. Seventy healthy women undergoing abdominal hysterectomy procedures with a standardized thiopental-sufentanil-desflurane-nitrous oxide anesthetic technique were randomly assigned to one of seven treatment groups (10 patients each). After a tracheal intubating dose of vecuronium 100 μg/kg (Groups 1 and 2), rocuronium 600 μg/kg (Groups 3 and 4), or mivacurium 250 μg/kg (Groups 5, 6, and 7), patients received vecuronium, 25 μg/kg (Groups 1 and 6), rocuronium 150 μg/kg (Groups 3 and 7), or mivacurium 50 μg/kg (Groups 2, 4, and 5) for maintenance of neuromuscular blockade. Neuromuscular function was assessed using electromyography, with a train-of-four mode of stimulation at the wrist every 10 s. The clinical duration (time for T₁ to return to 25% of baseline) of the maintenance dose of mivacurium was significantly longer after an intubating dose of rocuronium (40 ± 8 min) and vecuronium (28 ± 6 min) than after mivacurium (12 ± 3 min). The clinical duration of maintenance doses of vecuronium (18 ± 6 min) and rocuronium (13 ± 2 min) were significantly shorter after an intubating dose of mivacurium than that after an intubating dose of vecuronium (30 ± 5 min) or rocuronium (42 ± 12 min), respectively. These data suggest that with consecutive administration of neuromuscular blocking drugs, the initial duration of action depends more on the kinetics of the first neuromuscular blocking drug than the subsequent drug. Thus, there appears to be no clinical advantage in using mivacurium for maintenance of neuromuscular blockade after initial administration of rocuronium or vecuronium.