Intra‐ and postoperative low‐dose ketamine for adolescent idiopathic scoliosis surgery: a randomized controlled trial

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.