Decreased mivacurium constant infusion requirements with defasciculating doses of pancuronium.

This study was designed to verify a technique in which the pharmacologic profile of mivacurium infusions could be altered by small doses of pancuronium to reduce the infusion requirement without altering the subsequent recovery kinetics. Thirty ASA physical status I or II patients were randomized into two groups in a blinded fashion. One group was administered pancuronium 10 micrograms/kg followed by pancuronium 2.5 micrograms.kg-1.h-1 thereafter. The control group was given identical volumes of saline. Subsequently, all patients were given an initial bolus of mivacurium, and anesthesia was maintained using a nitrous oxide/ alfentanil technique. When the thenar electromyogram response to supramaximal train-of-four stimulation returned to 5% of baseline, a mivacurium infusion was begun in both groups, and the infusion rate required to maintain the electromyographic response at 1%-10% of baseline was determined. At the conclusion of the procedure, the infusion was terminated and the recovery profile ascertained. The mivacurium infusion requirement for the group receiving the pancuronium supplementation was 2.77 +/- 1.38 micrograms.kg-1.min-1 (mean +/- SD), which represented a 49% decrease compared with the group that used mivacurium alone which required an infusion rate of 5.43 +/- 1.85 micrograms.kg-1.min-1. No statistically significant difference was found in the recovery profiles of the two groups when the infusion was terminated. We conclude that the addition of a small amount of pancuronium decreased the required mivacurium infusion rate by nearly 50% without affecting the spontaneous recovery when terminating the infusion.