The Effects of Mixture of Mivacurium and Vecuronium on Neuromuscular Blockade during General Anesthesia

Background: This study was designed to examine the interactions between mivacurium and vecuronium when administered during a standardized technique. Methods: Eighty patients (ASA physical status I or II) were randomly assigned to one of four groups (n=20). Their neuromuscular function was measured in response to ulnar nerve supramaximal square-wave TOF stimulation at 10-sec intervals. After the attainment of a stable baseline neuromuscular response, the patients were randomly assigned to receive a rapid iv bolus of either: (1) 3M group (n=20): mivacurium 0.21 mg/kg. Alone, or (2) 2M1V group (n=20): mivacurium 0.14 mg/kg plus vecuronium 0.05 mg/kg, or (3) 1M2V group (n=20): mivacurium 0.07 mg/kg plus vecuronium 0.10 mg/kg, or (4) 3V group (n=20): vecuronium 0.15 mg/kg alone. The onset time of the neuromuscular block, time of recovery of T1 to 25% and reblock time (the time from the reinjection of vecuronium at the time of recovery of T1 to 25% to the time of recovery of T1 to 25%: T25-25) were measured. The intubating condition was evaluated clinically with a scoring system. Results: The onset of block in the 3M group was 33% slower than in the 3V group. The time durations until 25% recovery in the 2M1V, 1M2V and 3V groups were longer than in the 3M group, and the durations in the 1M2V and 3V groups were longer than in the 2M1V group. The T25-25 reblock times of the 2M1V, 1M2V and 3V groups were prolonged in comparison to that of the 3M group. There was no difference in intubating conditions between any of the groups. Conclusions: A combination of mivacurium with vecuronium provides rates of onset and duration of block which are more effective than an equivalent dose of mivacuriun alone as an additive reaction. (Korean J Anesthesiol 1999; 37: 6∼12)