Induction of general anaesthesia by effect-site target-controlled infusion of propofol: influence of pharmacokinetic model and ke0 value.

We studied the use of a new ke0 value (0.6 min(-1)) for the Marsh pharmacokinetic model for propofol. Speed of induction and side-effects produced were compared with three other target-controlled infusion systems. Eighty patients of ASA physical status 1-2 were studied in four groups in a prospective, randomised study. Median (IQR [range]) induction times were shorter with the Marsh model in effect-site control mode with a ke0 of either 0.6 min(-1) (81 (61-101 [49-302])s, p < 0.01), or 1.2 min(-1) (78 (68-208 [51-325])s, p < 0.05), than with the Marsh model in blood concentration control (132 (90-246 [57-435])). The Schnider model in effect-site control produced induction times that were longer (298 (282-398 [58-513])s) than those observed with the Marsh model in blood control (p < 0.05), or either effect-site control mode (p < 0.001). There were no differences in the magnitude of blood pressure changes or frequency of apnoea between groups.