Experience with vecuronium during long-lasting surgery.

Our knowledge of the possible cumulative properties of vecuronium is limited. Previous studies have shown a tendency towards an increased duration of effect, a slightly prolonged recovery time, as well as an increased variation in duration of effect. We have studied 15 patients scheduled for middle-ear surgery. During i.v. N2O-O2 anaesthesia the twitch response of the adductor pollicis muscle was recorded after supramaximal stimulation of the ulnar nerve at the wrist. Prior to tracheal intubation a bolus dose of vecuronium was given (0.08 mg/kg body weight). During surgery supplementary doses of 0.02 mg/kg body weight were given at a train-of-four (TOF) ratio of 0.25. The duration of effect (DUR-IT-25) and recovery time from a TOF ratio of 0.10 to 0.25 (Recovery-IT-10-25) were recorded. When comparing 10 iteration doses, the mean DUR-IT-25 in the 15 patients studied showed only minor variations (n.s.). Each patient had a near constant interval between the iteration doses; however, a noteworthy variation between individuals was found. Recovery-IT-10-25 was 250 +/- 80 (mean +/- s.d.) 240 +/- 80 and 260 +/- 80 s comparing the second, sixth and tenth iteration doses, respectively. In conclusion, the duration of effect varied considerably between patients. Each patient showed, however, a near constant iteration interval and a recovery time with only small variations. This indicates that cumulation is unlikely to exist following repetitive administration of vecuronium of 0.02 mg/kg body weight.