Accelerated onset and delayed recovery of neuromuscular block induced by mivacurium preceded by pancuronium in children.

The goal of this study was to describe a technique which could shorten the time from mivacurium administration to peak neuromuscular block (NMB) after administration of the maximum recommended dose of mivacurium. Forty-eight pediatric patients were randomized into three groups and studied during nitrous oxide-alfentanil-thiopental anesthesia. Every patient received two blinded injections 3 min apart: either 15 micrograms/kg of pancuronium in 1 mL of saline followed by 170 or 200 micrograms/kg of mivacurium or saline followed by 200 micrograms/kg of mivacurium. Intravenous induction of anesthesia followed the first injection. Thenar electromyogram response to supramaximum train-of-four stimulation of the ulnar nerve at 10-s intervals was used for neuromuscular monitoring. Pretreatment with pancuronium significantly shortened the time to NMB and prolonged spontaneous recovery from NMB in comparison to the temporal course of NMB after administration of 200 micrograms/kg of mivacurium. Time from injection to 90% NMB averaged 116 (SEM 11) s after administration of 200 micrograms/kg of mivacurium, and 71 (7) s and 94 (11) s when 200 micrograms/kg or 170 micrograms/kg of mivacurium, respectively, was preceded by pancuronium (P = 0.0095). Mean times from injection to recovery of neuromuscular function to > 25% of baseline (T25) and to train-of-four ratio of 0.75 were 9.1 (0.7) and 15.8 (1.2) min, respectively, after administration of 200 micrograms/kg of mivacurium alone. T25 and train-of-four of 0.75 occurred significantly later at 21.9 (1.8) and 35.0 (2.8) min, respectively (P = 0.0001), when 200 micrograms/kg of mivacurium was preceded by 15 micrograms/kg of pancuronium.(ABSTRACT TRUNCATED AT 250 WORDS)