Sympathomimetic effects of low-dose S(+)-ketamine. Effect of propofol dosage

Background. In analgetic dosages ketamine has stimulatory effects on the cardiovascular system, which limits its use in patients with heart disease. The aim of this study was to clarify whether low-dose S(+)-ketamine used to prevent chronic pain similarly stimulates the cardiovascular system and to determine the impact of propofol dosage on this effect. Methods. A total of 80 patients undergoing surgery under spinal or epidural anesthesia were randomly assigned to receive double-blinded S(+)-ketamine [0.25 mg/kg body weight (BW) bolus followed by infusion of 0.06 mg/kg BW/h] or placebo in the presence of continuous propofol infusion (2-5 mg/kg BW/h). The heart rate, blood pressure and calculated rate-pressure product (RPP) were monitored. Results. Following the S(+)-ketamine bolus, the heart rate, blood pressure and RPP increased significantly. In the presence of a propofol dosage > 3 mg/kg BW/h the stimulatory cardiovascular effect could no longer be observed. Conclusion. Even low-dose S(+)-ketamine has a stimulatory effect on the cardiovascular system. This stimulatory effect is nullified in the presence of a continuous propofol infusion at a dosage of more than 3 mg/kg BW/h.