PHARMACOKINETICS OF PROPOFOL INFUSION IN ASIAN PATIENTS UNDERGOING CORONARY-ARTERY BYPASS-GRAFTING

The pharmacokinetics of propofol was studied in 11 Asian patients with fentanyl-isoflurane anaesthesia during cardiopulmonary bypass (CPB) a nd undergoing elective coronary artery bypass grafting (CABG). Instead of the usual increments of morphine and a benzodiazepine, propofol (4 mg/kg/h) was initiated at the start of CPB and ceased at CPB separati on, Whole blood propofol concentrations were determined during and pos tinfusion using highperformance liquid chromatography with fluorescenc e detection. Data from four patients seemed to fit a two-compartment m odel, whereas those from seven patients were significantly (F test, p < 0.05) better fitted to a three-compartment model. The pharmacokineti c parameters were as follows: The mean (SD) of the initial distributio n phase t(1/2 pi), intermediate distribution phase t(1/2 alpha), and e limination phase t(1/2 beta) were 2.22 (1.04) min, 42.9 (16.4) min, an d 370 (138) min, respectively. The mean clearance of 1.31 (0.50) L/min was lower than those reported from other studies, whereas the mean bl ood concentration of 2.2 (1.0) mg/L at the 1-h infusion period was hig her. The mean calculated apparent C-ss was 3.9 (1.5) mg/L. The low cle arance is likely to be due to hemodynamic changes during CPB and CABG, thereby affecting drug distribution and blood flow to the liver.