[Estimated blood concentration of rocuronium administrated by continuous infusion to maintain an appropriate neuromuscular blockade under propofol anesthesia].

We managed 10 cases of propofol anesthesia with rocuronium, and recorded the time course of the neuromuscular blockade evaluated through accelerometry, as well as the estimated blood concentrations of rocuronium calculated from the administration history with a pharmacokinetic simulation analysis. Rocuronium was injected at 0.6 mg x kg(-1) initially, and the infusion rates were managed in order to maintain a twitch height at 3-10% of the control. The mean estimated rocuronium concentration (1.6 microg x ml(-1)) in our study was similar to the measured blood concentrations at the appropriate neuromuscular blockade that was previously reported. The estimated rocuronium concentrations at the appropriate neuromuscular blockade showed twice the inter-individual difference, and the time from the initial bolus of rocuronium to the spontaneous recovery with a twitch height of 5% showed a good relationship with the estimated rocuronium concentrations at the appropriate neuromuscular blockade. The time to spontaneous recovery with a twitch height of 25% and a reappearance of the fourth response in train-of-four ratio (TOF ratio) nerve stimulation was twenty minutes, even after a five-hour infusion, and was not affected by the length of the infusion. Thus, continuous infusion of rocuronium might be an effective and safe way to maintain appropriate neuromuscular blockade.