Variability of duration of action of neuromuscular‐blocking drugs in elderly patients

Abstract

Background:  Steroid‐based, non‐depolarizing neuromuscular‐blocking (NMB) drugs (e.g. rocuronium, vecuronium) are characterized by organ‐dependent elimination and significantly longer durations of action in elderly compared to young patients. Cisatracurium is a benzylisoquinolinium NMB drug with a duration of action not altered by ageing. The objective of the study was to determine if elderly patients had less variability in duration of action with 2 × ED95 of cisatracurium compared to equipotent doses of rocuronium or vecuronium.Methods:  Informed consent was obtained from 66 elderly patients with normal renal and liver function. Preoperative midazolam (1 mg) was given IV. The anaesthestic induction was with 5 mg kg−1 thiopental and 2 µg kg−1 fentanyl. The patients received 0.6 mg kg−1 rocuronium, 0.1 mg kg−1 vecuronium or 0.1 mg kg−1 cisatracurium. Anaesthetic maintenance was with sevoflurane in oxygen/nitrous oxide. Neuromuscular‐blocking duration of action was defined as the return of T1 twitch height to 25% of control. Variability was determined by subtracting the actual duration of action from the mean duration of action for each drug.Results:  The durations of action (range, min) were: cisatracurium, 37–81; vecuronium, 35–137; and rocuronium, 33–119. The median of the variability of duration was significantly less with cisatracurium (7 min) compared to vecuronium (18 min) and rocuronium (18 min) (P < 0.05).Conclusion:  When used with sevoflurane/N2O, there was a two‐fold greater variability of duration of neuromuscular blockade in elderly patients receiving rocuronium or vecuronium compared with cisatracurium.