Quantitation of the interaction of rocuronium bromide with etomidate, fentanyl, midazolam, propofol, thiopentone, and isoflurane using closed-loop feedback control of infusion of rocuronium.

Sixty patients were randomly assigned to one of six groups (n = 10 in each case) in which anaesthesia was induced and maintained with etomidate, fentanyl, midazolam, propofol or with thiopentone and N2O, or isoflurane and N2O. After obtaining control measurements, rocuronium 0.6 mg kg-1 was given for intubation followed by an infusion, controlled by closed-loop feedback at 90% block. The steady-state rates of infusion were (in the same order) 0.64 +/- 0.22, 0.60 +/- 0.15, 0.61 +/- 0.21, 0.67 +/- 0.31, 0.63 +/- 0.15 and 0.39 +/- 0.17 mg kg-1 h-1 (Mean +/- SD). The intravenous agents did not interact with recuronium to any clinically significant degree. Isoflurane reduced the requirements by 35-40%.