Efficacy of Continuous S(+)-Ketamine Infusion for Postoperative Pain Control: A Randomized Placebo-Controlled Trial

Aim. A double-blind, randomized, placebo-controlled trial was designed to evaluate the efficacy of continuous intraoperative infusion of S(+)-ketamine under intravenous anesthesia with target-controlled infusion of remifentanil and propofol for postoperative pain control. Methods. Forty-eight patients undergoing laparoscopic cholecystectomy were assigned to receive continuous S(+)-ketamine infusion at a rate of 0.3 mg·kg(-1)·h(-1) (n = 24, intervention group) or an equivalent volume of saline at the same rate (n = 24, placebo group). The same target-controlled intravenous anesthesia was induced in both groups. Pain was assessed using a 0 to 10 verbal numeric rating scale during the first 12 postoperative hours. Pain scores and morphine consumption were recorded in the postanesthesia care unit (PACU) and at 4 and 12 hours after surgery. Results. Pain scores were lower in the intervention group at all time points. Morphine consumption did not differ significantly between groups during PACU stay, but it was significantly lower in the intervention group at each time point after PACU discharge (P = 0.0061). At 12 hours after surgery, cumulative morphine consumption was also lower in the intervention group (5.200 ± 2.707) than in the placebo group (7.525 ± 1.872). Conclusions. Continuous S(+)-ketamine infusion during laparoscopic cholecystectomy under target-controlled intravenous anesthesia provided better postoperative pain control than placebo, reducing morphine requirement. Trial Registration. This trial is registered with ClinicalTrials.gov NCT02421913.