[Optimal dosage strategies in total intravenous anesthesia using propofol and ketamine]

The combination of propofol and ketamine for total intravenous anesthesia was investigated; the intention was to minimize the side effects of each drug by the concomitant application of the other drug. METHODS. Twenty patients scheduled for lower abdominal interventions were divided into two groups. In the first group anesthesia was induced and maintained by a simple administration regimen based upon pharmacokinetic principles. Ketamine and propofol were given as bolus injections (60 mg each) with a time interval of 60 s for induction followed by a two-step infusion regimen for propofol (15.5 mg/min) and later on by an additional ketamine infusion (1-2 mg/min). Bolus injections (20 mg) of ketamine were administered to increase the depth of anesthesia if necessary (Fig. 1). The second group received propofol and ketamine by microprocessor-controlled infusion pumps requiring the anesthetist to operate a single dial to preset the desired blood levels of both drugs according to the needs of the individual patient (Fig. 2). RESULTS. There were no difference (Table 1) between the two groups in the demographic data of the patients or duration of surgery (30-120 min). The total doses of propofol (750 +/- 262 vs 624 +/- 468 mg) and ketamine (158 +/- 41 vs 99 +/- 48 mg) were smaller in the computer-controlled infusion group, though this difference just failed to be significant. The hemodynamic changes during induction were minor, with a small nonsignificant increase in all parameters (Fig. 3) for 10 min. The controllability of the pharmacodynamic effects of both drugs during anesthesia was very satisfactory in the computer-assisted infusion group and quite satisfactory in the first group. There were no psychic disturbances during induction of or recovery from anesthesia. Respiration was adequate within a few minutes after the end of surgery. The patients were awake about 10 min later and fully oriented after 20 min. No major side effects were observed with this anesthetic technique. CONCLUSION. Total intravenous anesthesia with propofol and ketamine proved to be very satisfactory from a clinical point of view. The major known side effects of propofol (reduced hemodynamics during induction) and ketamine (psychic disturbances and cardiovascular stimulation) were absent and respiratory function was adequate after the end of surgery. This technique, therefore, can be used in risk patients and under disaster conditions when i.v. access is the only possible route of drug administration. The use of computer-assisted infusion pumps markedly enhances handling and controllability of total i.v. anesthesia.