[Augmentation of the neuromuscular blocking effect of mivacurium during inhalation anesthesia with desflurane, sevoflorane and isoflurane in comparison with total intravenous anesthesia]

Abstract

To evaluate the enhancement of mivacurium-induced neuromuscular block by potent inhalational anaesthetic agents, dose-effect curves for mivacurium were determined in 84 patients scheduled for minor elective surgery during anaesthesia with 1.5 MAC (70% N2O) desflurane, sevoflurane and isoflurane and compared with those under total intravenous anaesthesia (TIVA). Acceleromyography (TOF-Guard) and train of four (TOF) stimulation of the ulnar nerve were used (2 Hz every 12 s). Mivacurium was administered in increments of 25 micrograms kg-1 until a depression of T1 > 95% was reached. ANOVA was used for statistical analysis (alpha = 0.05, beta = 0.2). The depression of T1 during potent inhalational anaesthesia was enhanced compared with TIVA. The ED50 and ED95 of mivacurium were 27 +/- 11 (SD) and 58 +/- 26 micrograms kg-1 for desflurane; 28 +/- 10 and 64 +/- 23 micrograms kg-1 for sevoflurane; and 27 +/- 13 and 55 +/- 27 micrograms kg-1 for isoflurane and were significantly lower than the 35 +/- 7 and 71 +/- 20 micrograms kg-1 for TIVA. The duration 25% revealed a significant difference between the volatile anaesthetic groups (10 +/- 2, 11 +/- 3, 11 +/- 3 min respectively) and the TIVA control group (8 +/- 3 min). The recovery index 25/75 and TOFO.80 were significantly prolonged by desflurane, sevoflurane and isoflurane compared with TIVA (RI25/75 9 +/- 4, 9 +/- 4, 10 +/- 5 respectively vs. 5 +/- 2 min; TOFO.80 27 +/- 10, 28 +/- 9, 29 +/- 9 respectively vs. 18 +/- 4 min). We conclude that the neuromuscular blocking effect of mivacurium is enhanced during anaesthesia with desflurane, isoflurane and sevoflurane compared with TIVA. The duration of action and the recovery time are prolonged. The dose of mivacurium used should be reduced if anaesthesia is maintained with volatile anaesthetics.