TOTAL I.V. ANAESTHESIA WITH PROPOFOL AND ALFENTANIL: DOSE REQUIREMENTS FOR PROPOFOL AND THE EFFECT OF PREMEDICATION WITH CLONIDINE

We determined in 51 healthy patients undergoing body surfacesurgery the dose requirements for propofol, as part of a totali.v. anaesthesia technique with an alfentanil infusion. Afterpremedication with temazepam, patients received alfentanil 50µg kg^–1 followed by an infusion of 50 µg kg^–1h^–1. Patients were anaesthetized with a loading dose ofpropofol followed by a three-stage infusion designed to reachone of five preselected blood concentrations of propofol. Themotor response to the initial surgical incision was noted andprobit analysis was used to derive the ED₅₀ (2.94 mg kg^–1h^–1; 95% confidence limits: 2.35–3.37 mg kg^–1h^–1). and ED₉₅ (4.98 mg kg^–1 h^–1; 95% limits:4.13–8.8 mg kg^–1 h^–1) for the final propololinfusion rate under these conditions. Whole blood concentrationof propofol at the time of the incision was related linearlyto the infusion rate and the EC₅₀ and EC₉₅ (probit analysis)were derived as 1.44 (95% confidence limits 0.62–1.87)and 4.05 (95% confidence limits 2.78–30.5) µg ml^–1,respectively. Postoperative recovery was rapid, uncomplicatedand uneventful. In a subgroup of eight patients, the additionof clonidine 0.6mg to the premedication significantly decreasedthe requirement for propofol (P <0.05) during surgery, butresulted in prolonged recovery times. Pilot study presented to the Anaesthetic Research Society, June24, 1988 [1].