SEVOFLURANE AND ISOFLURANE IMPAIR EDROPHONIUM REVERSAL OF VECURONIUM-INDUCED NEUROMUSCULAR BLOCK

Purpose: A dose-response relationship study for edrophonium to examine the modification of volatile anaesthetics on reversal of vecuronium b lock. Methods: One hundred and twenty ASA (I-II) patients were anaesth etized with sevoflurane, isoflurane (1 minimum alveolar anaesthetic co ncentration [MAC] end-tidal concentration), or fentanyl-diazepam anaes thesia, in combination with 66% nitrous oxide (n = 40 for each group). The evoked electromyogram (EMG) response of the abductor digiti minim i was monitored at 20 sec intervals following train-of-four (TOF) stim ulation of the ulnar nerve. The initial neuromuscular block was produc ed by vecuronium 100 mu g . kg(-1). When the amplitude of the first re sponse (T-1) had spontaneously recovered to 10% of the control, edroph onium (0, 125, 400, 700 or 1000 mu g . kg(-1); eight patients each) wa s randomly administered and the ratio of the fourth TOF to the first r esponse (TOFR) was monitored at one minute intervals for 10 min. Resul ts: Sevoflurane and isoflurane impaired the; edrophonium-assisted TOFR recovery in an edrophonium dose and lime dependent manner. The dose-r esponse curves at 10 min exhibited a greater shift to the right in the sevoflurane and isoflurane groups than in the fentanyl-diazepam-nitro us oxide group (P < 0.05). Higher ED(50) values (the edrophonium dose required to obtain TOFR value of 50%) in the sevoflurane (>1000 mu g . kg(-1)) and isoflurane groups (851 mu g . kg(-1)) were observed than in the fentanyl-diazepam-nitrous oxide group (339 mu g . kg(-1)) (P < 0.05). Conclusion: One MAC sevoflurane and isoflurane anaesthesia impa ir edrophonium reversal of vecuronium block to a similar degree.