Rapacuronium recovery characteristics and infusion requirements during inhalation versus propofol-based anaesthesia

We examined the effect of four maintenance anaesthetics on the neuromuscular blocking activity and spontaneous recovery characteristics after a short-term infusion of rapacuronium. Eighty ASA I-III adult patients undergoing elective surgery were studied at four centres. Anaesthesia was induced with propofol 1.5-2.5 mg kg^-1 and fentanyl 1-2 μg kg^-1, followed by a bolus of rapacuronium 1.5 mg kg^-1. The patients were randomized to receive either desflurane (2-4% end-tidal, ET), sevoflurane (0.75-1.5% ET), isoflurane (0.4-0.8% ET), or a propofol infusion (75-150 μg kg^-1 min^-1) for maintenance of anaesthesia in combination with nitrous oxide (60-70%) in oxygen. When the first twitch (T₁) of a train-of-four stimulus (using the TOF Guard(®) accelerometer) returned to 5%, an infusion of rapacuronium was started at 3 mg kg^-1 h^-1 and adjusted to maintain T₁/T₀ at 10%. The duration of infusion lasted between 45 and 60 min, and the average infusion rates of rapacuronium were similar in all groups, ranging from 1.6 to 2.5 mg kg^{- 1} h^-1. There were no significant differences among the groups in the times for T₁/T₀ to return to 25%, 75% or 90%, or for T₄/T₁ to return to 70% and 80% upon discontinuation of the infusion. When potent inhalation anaesthetics are used in clinically relevant concentrations for maintenance of anaesthesia, the neuromuscular recovery profile of rapacuronium administered as a variable-rate infusion for up to I h is similar to that found with a propofol-based anaesthetic technique.