Repetitive administration of pancuronium and vecuronium (Org NC 45, Norcuron) in patients undergoing long lasting operations.

SUMMARY Fifty-one patients undergoing surgical procedures which required at least 2 h of anaesthesia were randomly divided into two groups receiving either pancuronium or vecuronium (Org NC 45) as a muscle relaxant under evoked twitch tension control. In the absence of halogenated inhalation anaesthetics, both drugs were administered by initial bolus injection of 0.1 mg kg -1 , followed by increments of 0.025 mg kg -1 when twitch height had recovered to 25% of control. In all cases the initial dose produced total neuromuscular blockade and satisfactory intubation conditions within 2–4min. The time of onset was slightly shorter with vecuronium than with pancuronium. The mean duration from the end of injection to 25% recovery of the initial arid the maintenance doses was three and four tunes longer with pancuronium than with vecuronium, respectively. The average drug requirement per hour to maintain at least 75% block was one maintenance dose of pancuronium 0.025mg kg -1 and four maintenance doses of vecuronium 0.1 mg kg -1 . The overall recovery time (25% to 75% twitch height) irrespective of the number of maintenance doses was 40±14min with pancuronium and 15±8min with vecuronium (mean±SD). Some cumulation was observed with pancuronium, particularly in terms of prolonged recovery time. With vecuronium, both duration of action of maintenance doses and recovery time did not depend on the number of maintenance doses. In both groups of patients no cardiovascular or other side-effects were observed. It is concluded that vecuronium is a true intermediate-acting non-depolanzing muscle relaxant. Its lack of cumulation favours the maintenance of profound neuromuscular blockade until close to the end of operation without the risk of an unduly long recovery time.