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

Abstract

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.