MUSCLE PARALYSIS BY ROCURONIUM DURING HALOTHANE, ENFLURANE, ISOFLURANE, AND TOTAL INTRAVENOUS ANESTHESIA

We determined the dose-response relationship, the onset time, the dura tion, and the recovery time of a rocuronium neuromuscular block under four anesthesia techniques. Patients were equally randomized to four d ifferent groups (n = 20) receiving 0.5%-l% halothane, 1.5%-2% enfluran e, 1.2%-1.8% isoflurane end-tidal concentration in 34%/66% O2/N2O, or 6.0 mg.kg-1.h-1 propofol without N2O for anesthesia and alfentanil for analgesia. Strength of thumb adduction in response to single and trai n-of-four stimulation of the ulnar nerve was quantitated. Rocuronium 0 .15, 0.2, 0.25, and 0.3 mg/kg were given intravenously. When maximal d epression of twitch tension occurred, supplemental doses up to a total of 0.5 mg/kg were given. If required, additional doses of 0.15 mg/kg were given at 25% recovery of control twitch tension. Standard hemodyn amics, end-tidal CO2, and anesthetic gas concentrations were monitored continuously. The mean ED50 (SD) was 0.133 (+/-0.009) mg/kg for the h alothane group, 0.118 (+/-0.012) mg/kg for the enflurane group, 0.069 (+/-0.026) mg/kg for the isoflurane group, and 0.167 (+/-0.007) mg/kg for the total intravenous anesthesia (TIVA) group, respectively There was a statistically significant difference between the halothane and T IVA, and between the enflurane and TIVA groups (P < 0.05). Rocuronium has a short onset time and an intermediate duration of action. The neu romuscular blocking potency and pharmacodynamic profile are moderately influenced by volatile anesthetics.