Effect-site modelling of propofol using auditory evoked potentials

Auditory evoked potentials (AEP) were used to monitor central nervoussystem effects during induction and recovery from anaesthesia produced byinfusion of propofol 30 mg kg-1 h-1 in 22 healthy male patients. Non-parametric and parametric modelling techniques were used successfully tocalculate the parameter keo which linked pharmacokinetic withpharmacodynamic aspects of drug action in only 15 of the study patients. Inthe non-parametric analysis, keo was found to have a mean value of 0.2(range 0.1-0.36) min-1. Estimation of keo allowed calculation of theeffect-site concentration (Ce50) associated with 50% of AEP effect for thepopulation (2.08 micrograms ml-1; 95% confidence limits 1.7-2.45). Therewere no significant differences between keo values calculated bynon-parametric and individual parametric modelling techniques. Duringrecovery, 50% of patients demonstrated evidence of waking at an effect-siteconcentration of 2.28 micrograms ml-1.