THE INFLUENCE OF ISOFLURANE ON A CONTINUOUS-INFUSION OF MIVACURIUM

Sixty surgical patients were studied to evaluate the neuromuscular eff ects of mivacurium 0.15 mg.kg(-1) (2 x ED(95)) for tracheal intubation . After intubation the patients were randomly allocated to receive alf entanil with either propofol (starting with 9 mg.kg(-1) h(-1), reducin g to 6mg.kg(-1) h(-1) after 20 min) or isoflurane (0.5% end-tidal). In addition, all the patients were given a continuous infusion of miracu rium 10 mu g.kg(-1) min(-1) after tracheal intubation which was adjust ed to maintain 90% depression of T-1. Following mivacurium 0.15 mg.kg( -1) T decreased below 25% in all but four patients. Mean (SD)percentag e maximum block attained was 92.9% (12.5) after 309 (89)s. Tracheal in tubation was completed 232 (155) s after administration of the relaxan t and intubating conditions were graded as 'excellent' or 'good' in 56 patients. Although the mean (SD) mivacurium infusion rate for maintai ning T-1 at 10% was higher in the propofol group, 4.8 (2.1) compared w ith 4.4 (2.0) mu g.kg(-1) min(-1) in the isoflurane group, this was no t significantly different (p > 0.05). The mean (SD) recovery index was prolonged in the isoflurane patients, 757 (508)s, compared to those r eceiving propofol, 466 (219)s (p < 0.05).