British journal of anaesthesia
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We have studied the pharmacokinetics of a single bolus of rocuronium (Org 9426), followed by an infusion, in eight patients during anaesthesia with halothane and nitrous oxide in oxygen. Neuromuscular block was monitored using train-of-four (TOF) stimulation and recording the force of contraction of the adductor pollicis muscle. Rocuronium was administered as an initial bolus dose of 0.45 mg kg-1 followed by an infusion adjusted manually to maintain T1 (first response in the TOF) at 10% of control. ⋯ The rate of clearance, mean residence time and volume of distribution at steady state were 3.3 (0.77) ml kg-1 min-1, 67.2 (18.8) min and 212.5 (40.1) ml kg-1, respectively. The distribution (T1/2 alpha) and elimination (T1/2 beta) half-lives were 7.5 (3.33) min and 85.6 (18.4) min, respectively. These values were not significantly different from previously published data for a single bolus dose of rocuronium.
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We have compared the potency of vecuronium given to 12 smokers and 12 non-smokers during propofol-alfentanil-nitrous oxide anaesthesia. After obtaining individual dose-response curves, bolus doses of vecuronium were given to maintain neuromuscular block at 90-98% for 60 min. Adductor pollicis EMG was used to monitor neuromuscular block. ⋯ The dose of vecuronium to maintain 90-98% neuromuscular block was 25% higher in smokers than in non-smokers (96.80 vs 72.11 micrograms kg-1 h-1; P < 0.01). These data reflect the effects of smoking on neuromuscular block induced by vecuronium. The effect may be at the receptor level, although possible increased metabolism of vecuronium in smokers cannot be excluded.