Background: This study was designed to compare variability in the offset of two neuromuscular blocking agents with different elimination pathways.
Methods: The spontaneous recovery profiles of cisatracurium and vecuronium were compared in adult (18-64 years) and elderly (> or =65 years) patients receiving N2O/O2/fentanyl/propofol anaesthesia. Patients were randomised to receive an initial bolus dose and maintenance doses of 3xED95, respectively, 0.6xED95 for cisatracurium (0.15 and 0.03 mg.kg-1) or 2xED95, respectively, and 0.4xED95 for vecuronium (0.1 and 0.02 mg.kg(-1)), as recommended in their prescribing information. Administration of the study drugs was double-blinded, and neuromuscular transmission was monitored using mechanomyography of the evoked response of the adductor pollicis, following ulnar nerve stimulation.
Results: The clinically effective duration (minutes) of the initial bolus dose, defined as the mean time to 25% T1 recovery (+/-SD), for the adult and elderly patients was 53.5+/-9.8 and 57.3+/-11.5 for cisatracurium, respectively, and 34.1+/-9.0 and 47.5+/-14.4 for vecuronium, respectively. The duration of spontaneous sufficient recovery (SSR), defined as the mean (+/-SD) time interval in minutes from 25% T1 recovery to a T4:T1 ratio > or =0.8 after the last bolus dose, for the adult, respectively, elderly patients was 28.3+/-8.0 and 31.7+/-10.0 for cisatracurium and 38.5+/-13.2 and 60.3+/-26.1 for vecuronium.
Conclusion: Whereas both the clinically effective duration and the duration of SSR are comparable between the adult and the elderly patients receiving cisatracurium, they differ substantially between these two age groups for vecuronium. Furthermore, the variability in offset is significantly lower in patients receiving cisatracurium, especially in the elderly, which may be of particular clinical interest.