[A clinical study on total intravenous anesthesia with droperidol, fentanyl and ketamine--2. Pharmacokinetics following the end of continuous ketamine infusion].

Ten surgical patients who received various operative procedures including abdominal surgery and ENT surgery were the subjects of the pharmacokinetic study of total intravenous anesthesia with droperidol, fentanyl and ketamine. Six arterial samples were taken through an indwelling catheter in the left radial artery to measure plasma levels of ketamine and its metabolites by means of gas liquid chromatography. Two hours following the end of the ketamine infusion, plasma ketamine levels decreased to 14% of the control value (0.81 micrograms.ml-1), while metabolite I (K1) was still about 1.8 micrograms.ml-1 in the plasma. The control value of plasma ketamine just before the end of its infusion had not any significant relationship with the total dose of ketamine, total dose of fentanyl, blood loss or fluid given. The results of our study suggest that long continuous ketamine infusion would be safe as judged by its pharmacokinetics.