REDUCTION OF MIVACURIUM REQUIREMENTS BY SEVOFLURANE IN ADULTS AND CHILDREN

Abstract

S429 Introduction: Sevoflurane, like isoflurane and desflurane [1,2], is expected to decrease mivacurium requirements and prolong recovery. This study compared mivacurium infusion rates and recovery characteristics in adults and children during propofol/narcotic and sevoflurane anesthesia. Methods: After informed consent, 75 adult (20-65 yr) and 75 pediatric (2-12 yr), ASA 1-2, elective surgical patients were randomized to 3 groups to receive anesthesia with propofol/narcotic, 0.5 or 1.0 MAC sevoflurane. Blood was sampled for plasmacholinesterase estimation, and EMG neuromuscular monitoring (Datex Relaxograph: TOF every 10 sec, adductor pollicis) before mivacurium 0.25 mg/kg i.v. bolus. Mivacurium infusion commenced at 10 [micro sign]g/kg/min and was titrated to maintain 90-95% block. Rates were recorded every 5 min. At the end of surgery, the infusion was stopped and spontaneous recovery from mivacurium blockade monitored until TOF 0.7 was achieved. Results: Neither adults nor children showed demographic differences among groups. Plasmacholinesterase concentrations were normal (adults 4-12, children 6-16 KU/L). Mivacurium infusion rates, twice as high in children as in adults, decreased over time, and in proportion to sevoflurane concentration. Recovery was prolonged, but children recovered twice as quickly as adults (Table 1).Table 1Discussion: Sevoflurane halved mivacurium infusion requirements and doubled recovery times. Higher doses were needed in children, but recovery was faster than in adults. Mivacurium rates continued to decrease and, at 45 min, sevoflurane equilibration was incomplete at the neuromuscular junction.