[Clinical study on total intravenous anesthesia with droperidol, fentanyl and ketamine--3. Pharmacokinetics during prolonged continuous ketamine infusion].

A simple and precise method has been developed for the analysis of plasma ketamine and its metabolites using gas chromatography with flame ionization detection after elution by trifluoroacetic dehydride. Seven surgical patients who received total intravenous anesthesia with droperidol, fentanyl and ketamine anesthesia over 5 hours were the subjects of the study. During the anesthesia, ketamine levels were from 1.0 to 2.0 micrograms.ml-1. After the termination of ketamine infusion, their levels decreased gradually. Metabolites I levels were elevated gradually to about twofold of that of ketamine and remained high. Metabolite II was detected in only two patients and their levels were under 0.2 micrograms.ml-1. The results of our study suggest that this type of anesthesia of prolonged duration is safe as judged by the present pharmacokinetic study.