Pharmacokinetics of Propofol Infusions in Japanese Patients.

Abstract

The pharmacokinetic parameters of the intravenous anesthetic drug propofol were investigated. Propofol was administered using an infusion pump at variable rates (10, 8, 6 and 4 mg/kg/hr) to 15 Japanese patients undergoing surgery, as part of a protocol for the induction of general anesthesia that included the use of nitrous oxide and muscle relaxants. The weight of the patients was 56±10 kg (mean±SD). The blood propofol concentrations were determined using high performance liquid chromatography and ECD detection. Blood propofol concentrations were also measured when the patients awoke. The blood propofol concentrations were fitted by a three-compartment model using the maximum likelihood estimation. Bias, accuracy and precision between the measured and the predicted blood concentrations were calculated using the pharmacokinetic parameters obtained.The obtained elimination clearance (CL), of 49 ml/kg/min, was greater than that reported in a different propofol study in which the weight of the patients was 71±17 kg. The blood propofol concentration when the patients opened their eyes in response to a verbal command was 793.0±67 ng/ml (mean±SD). The prediction error calculated from our parameters (mean absolute error, 0.12, root mean squared error, 0.078), particularly that at awakening, was significantly smaller than that calculated from parameters obtained in a previous report. The pharmacokinetic parameters in this study were useful for the prediction of the propofol blood concentration, as was the application of a computer controlled infusion pump technique.