The influence of target concentration, equilibration rate constant (ke0 ) and pharmacokinetic model on the initial propofol dose delivered in effect-site target-controlled infusion.

Abstract

One advantage of effect-site target-controlled infusion is the administration of a larger initial dose of propofol to speed up the induction of anaesthesia. This dose is determined by the combination of the pharmacokinetic model parameters, the target setting and the blood-effect time-constant, ke0 . With the help of computer simulation, we determined the ke0 values required to deliver a range of initial doses with three pharmacokinetic models for propofol. With an effect site target of 4 μg.ml(-1) , in a 35-year-old, 170-cm tall, 70-kg male subject, the ke0 values delivering a dose of 1.75 mg.kg(-1) with the Marsh, Schnider and Eleveld models were 0.59 min(-1) , 0.20 min(-1) and 0.26 min(-1) , respectively. These ke0 values have the attractive feature that, when used to simulate the administration schemes used in two previous studies, predicted effect site concentrations at loss of consciousness were close to those required for maintenance of anaesthesia.