EFFECT OF ISOFLURANE AND SEVOFLURANE ON THE MAGNITUDE AND TIME-COURSEOF NEUROMUSCULAR BLOCK PRODUCED BY VECURONIUM, PANCURONIUM AND ATRACURIUM

We have compared the ability of equipotent concentrations of isofluran e and sevoflurane to enhance the effect of non-depolarizing neuromuscu lar blocking drugs. Ninety ASA I and II patients of both sexes, aged 1 8-50 yr, were stratified into three blocker groups (Vee, Pan and Atr), to undergo neuromuscular block with vecuronium (n = 30), pancuronium (n=30) or atracurium (n=30), respectively. Within each group, patients were allocated randomly to one of three anaesthetic subgroups to unde rgo maintenance of anaesthesia with: (1) alfentanil-nitrous oxide-oxyg en (n = 10); (2) alfentanil-nitrous oxide-oxygen-isoflurane (n = 10); or (3) alfentanil-nitrous oxide-oxygen-sevoflurane (n = 10) anaesthesi a. During maintenance of anaesthesia, end-tidal concentrations of isof lurane, sevoflurane and nitrous oxide were 0.95, 1.70 and 70%, respect ively. Both the evoked integrated electromyogram and mechanomyogram of the adductor pollicis brevis muscle were measured simultaneously. In the Vec and Pan groups, a total dose of 40 mu g kg(-1) of vecuronium o r pancuronium, respectively, was given, and in the Atr group a total d ose of atracurium 100 mu g kg(-1) Each blocker was given in four equal doses and administered cumulatively. We showed that 0.95% isoflurane and 1.70% sevoflurane (corresponding to 0.8 MAC of each inhalation ana esthetic, omitting the MAC contribution of nitrous oxide) augmented an d prolonged the neuromuscular block produced by vecuronium, pancuroniu m and atracurium to a similar degree.