Augmentation of the neuromuscular blocking effects of cisatracurium during desflurane, sevoflurane, isoflurane or total i.v. anaesthesia.

We have evaluated the enhancement of cisatracurium-induced neuromuscular block by potent inhalation anaesthetic agents, by constructing dose-effect curves for cisatracurium in 84 patients during anaesthesia with 1.5 MAC (70% nitrous oxide) desflurane, sevoflurane, isoflurane or total i.v. anaesthesia (TIVA). Acceleromyography (TOF-Guard) and train-of-four (TOF) stimulation of the ulnar nerve were used (2 Hz every 12 s). Cisatracurium was administered in increments of 15 micrograms kg-1 until depression of T1/T0 > 95% was reached. ANOVA was used for statistical analysis (alpha = 0.05, beta = 0.2). Depression of T1/T0 during potent inhalation anaesthesia was enhanced compared with TIVA. ED50 and ED95 values of cisatracurium were 15 (SD 5) and 34 (10) micrograms kg-1 for desflurane; 15 (4) and 32 (7) micrograms kg-1 for sevoflurane; and 15 (5) and 33 (9) micrograms kg-1 for isoflurane. These were significantly lower than the values for TIVA (21 (4) and 51 (13) micrograms kg-1) (P < 0.01 in each case). After equi-effective dosing, times to T1/T0 = 25% were similar in all groups (19 (7), 19 (5), 20 (5) vs 16 (4) min). Recovery index25-75% and time to a TOF ration of 0.70 were prolonged significantly by desflurane and sevoflurane compared with TIVA (18 (5), 19 (8) vs 12 (4) min and 43 (11), 44 (10) vs 35 (5) min, respectively), whereas the difference was not significant for isoflurane (14 (6) and 41 (7) min).