Background In this randomized controlled trial, we examined whether intra- and postoperative infusion of low-dose ketamine decreased postoperative morphine requirement and morphine-related adverse effects as nausea and vomiting after scoliosis surgery. Methods After IRB approval and informed consent, 36 patients, aged 10-19 years, undergoing posterior correction surgery for adolescent idiopathic scoliosis, were randomly allocated into two groups: intra- and postoperative ketamine infusion at a rate of 2 μg/kg/min until 48 h after surgery (ketamine group, n = 17) or infusion of an equal volume of saline (placebo group, n = 19). All patients were administered total intravenous anesthesia with propofol and remifentanil during surgery and intravenous morphine using a patient-controlled analgesia device after surgery. The primary outcome was cumulative morphine consumption in the initial 48 h after surgery. Pain scores (Numerical Rating Scale, NRS, 0-10), sedation scales, incidence of postoperative nausea and vomiting (PONV), and antiemetic consumption were recorded by nurses blinded to the study protocol for 48 h after surgery. Results Patient characteristics did not differ between the two groups. Cumulative morphine consumption for 48 h after surgery was significantly lower in the ketamine group compared to the placebo group (0.89 ± 0.08 mg/kg vs. 1.16 ± 0.07 mg/kg, 95% confidence interval for difference between the means, 0.03-0.48 mg/kg, P = 0.019). NRS pain, sedation scales, and incidence of PONV did not differ between the two groups. Antiemetic consumption was significantly smaller in ketamine group. Conclusions Intra- and postoperative infusion of low-dose ketamine reduced cumulative morphine consumption and antiemetic requirement for 48 h after surgery.
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