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Ketamine-induced sympathetic stimulation can be inhibited by administration of sedatives such as benzodiazepines, droperidol, or opioids. We have developed total intravenous anesthesia with ketamine in combination with droperidol and fentanyl (DFK) and have used this anesthetic method in more than 4000 surgical cases. In this study, we compared DFK in cardiac surgery with isoflurane-fentanyl anesthesia (AOI-F). Fourteen patients undergoing aortocoronary artery bypass graft surgery were randomly assigned to the DFK or AOI-F groups. The endocrine responses of the patients were evaluated from the plasma, levels of cortisol, antidiuretic hormone (ADH), atrial natriuretic peptide (ANP), and aldosterone. In both groups, anesthesia per se did not induced any significant changes in the hormones. Although cortisol and ADH increased during surgery, ANP and aldosterone did not change appreciably. All hormones were significantly elevated after the end of cardiopulmonary bypass. There were no significant differences in any of the hormones, blood pressure, and heart rate measured at different points in both groups. These results showed that DFK anesthesia as a total intravenous anesthesia deserves to be studied in more depth.

Cardiopulmonary bypass (CPB) makes prediction of any drug concentration diffcult because both hypothermia and hemodilution can alter the pharmacokinetics of the drug. Eleven patients undergoing cardiac surgery under CPB were anesthetized with continuous infusion of ketamine combined with intermittent administration of droperidol and fentanyl. The infusion rate of ketamine was 2 mg·kg·hr following a bolus administration of 1.5 mg·kg for the induction of anesthesia. Blood concentrations of ketamine and its main metabolite, norketamine, were measured at 0, 30, and 60 min after the start of and the end of CPB, and 0, 1, 2, and 24 h after the cessation of ketamine infusion. Hypothermia increased blood ketamine levels during CPB, but the norketamine levels did not change. Although acute hemodilution would decrease blood ketamine levels, their levels were already significantly increased at 30 min after CPB. Hypothermic factors have a more kinetically important role during CPB than hemodilution. Increases in blood norketamine levels following rewarming indicate that hypothermia could impair ketamine metabolism in the liver. Further increase in the plasma concentration of ketamine until 30 min after the end of CPB might be due to blood transfusion containing ketamine from the CPB reservoir.

Cardiopulmonary bypass (CPB) makes prediction of any drug concentration difficult because both hypothermia and hemodilution can alter the pharmacokinetics of the drug. Eleven patients undergoing cardiac surgery under CPB were anesthetized with continuous infusion of ketamine combined with intermittent administration of droperidol and fentanyl. The infusion rate of ketamine was 2 mg-kg ~-hr ~ following a bolus administration of t.5 mg.kg -~ for the induction of anesthesia. Blood concentrations of ketamine and its main metabolite, norketamine, were measured at 0, 30, and 60 rain after the start of and the end of CPB, and 0, 1,2, and 24 h after the cessation of ketamine infusion. Hypothermia increased blood ketamine levels during CPB, but the norketamine levels did not change. Although acute hemodilution would decrease blood ketamine levels, their levels were already significantly increased at 30 min after CPB. Hypothermic factors have a more kinetically important role during CPB than hemodilution. Increases in blood norketamine levels following rewarming indicate that hypothermia could impair ketamine metabolism in the liver. Further increase in the plasma concentration of ketamine until 30 rain after the end of CPB might be due to blood transfusion containing ketamine from the CPB reservoir.