Anaesthesia
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The accuracy of a computer-controlled infusion of midazolam, based on previously published pharmacokinetic parameters, was tested prospectively in 12 adult female patients undergoing general anaesthesia. Anaesthesia consisted of an initial bolus followed by an exponentially decreasing infusion of midazolam given according to body weight, fentanyl, nitrous oxide and vecuronium. Venous blood samples were taken at 15 min-intervals throughout the procedures and for 1-2 h postoperatively. ⋯ Retrospective fitting of an alternative set of published parameters for midazolam resulted in significant deterioration of the model. The precision was similar to that found in past studies of intravenous anaesthetic agents. Further improvement in the accuracy of midazolam infusion awaits improved understanding of the causes of pharmacokinetic variability.
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The ability of a target-controlled propofol infusion system to provide sedation for 40 patients undergoing surgery under regional blockade was assessed. Eighty-eight per cent of the total infusion time was at the desired sedation level with little oversedation. ⋯ The pharmacokinetic algorithm performed as well when used for sedation as for total intravenous anaesthesia. The predicted and measured blood propofol concentrations showed a bias of -12% and a precision of 34%.