comparison of effects and antagonism of vecuronium-induced neuromuscular blockade during sevoflurane and isoflurane anaesthesia

ABSTRACT

Volatile anaesthetic agents potentiate neuromuscular blocking agents and retard their rate of reversal. Patients divided into three groups, a control group [n= 18], isoflurane group [n=24] and sevoflurane group [n = 24]. The study examined the interactions of 1 MAC of isoflurane and sevoflurane [66% nitrous oxide in oxygen] with vecuronium. Accurate baseline value values [100% reference values for amplitudes of first response [T[1]] and ratio of fourth to the first T of response [T[4]-T[1]] were obtained. The dose response curves for vecuronium constructed in 54 patients [18 patients each]. The curves for both isoflurane and sevoflurane had a significant lefward shift compared with that for fentanyl-nitrous oxide anaesthesia [P<0.01] Fig. 1]. When surgery was complete, recovery from neuromuscular block was allowed to occur spontaneously in three groups [part 1]. When the amplitude of the first response T[1] had recovered to 50% of control, subsequently we compared the spontenous recovery rate of the ratio of the fourth to the first TOF response [T[4]-T[1]] at 3 min intervals during the 15-min period in the presence of two volatile anaesthetics or after discontinuation of administration of anaesthetics [Fig.2]. Times from reversal to T[1]=25, 50 and 60% and TOF =0.6 were recorded, mean [SD] times to train of four ratio =0.6 in isoflurane and sevoflurane groups were 330 [134] and 353 [130] s, respectively. The mean [SD] times to single twich response T[1] = 25, 50 and 60% in the isoflurane group were 50 [35], 103 [40] and 252 [87] s, respectively, and in sevoflurane group were 93 [37], 205[90] and 254 [124] s respectively [Table 2]. The rate of recovery of T[4] T[1] was significantly greater when both anaesthetics were discontinued. However, this rate was similar for both anaesthetics, suggesting that the mechanism or action or the two anaesthetics is similar. The T[4] T[1] values recovered spontaneously more rapidly in both stop groups than in both stable groups [P<0.05]. There was no significant differences in the spontaneous T[4] T[1] recovery rate between the I [stop] and S [stop] groups or between the I [stop] and S [stable] groups [Fig.2]. After completion of the study, residual neuromuscular block was studied [part 2], evoked reversal characteristics of vecuronium using edrophonium and compared them this those obtained following neostigmine. It is concluded that edrophonium antgonizas more rapidly residual vecuronium- induced neuromuscular blockade [Table 3]