Intra- and postoperative very low dose intravenous ketamine infusion does not increase pain relief after major spine surgery in patients with preoperative narcotic analgesic intake.

Objective: This study aims to demonstrate the analgesic efficacy and opioid-sparing effect of low dose ketamine in patients with preoperative narcotic intake undergoing major spine surgery.

Design: The study used a prospective, randomized, double-blinded, and placebo-controlled clinical trial.

Settings And Patients: We evaluated the analgesic efficacy and safety of low dose IV ketamine infusion after major spine surgery in patients with preoperative narcotic analgesic intake. Ketamine group received IV ketamine infusion (2 µg/kg/min) and saline group received saline intraoperatively and the first 24 hours postoperatively. In addition, all patients received IV patient-controlled hydromorphone and epidural bupivacaine.

Outcome Measures: Pain scores, narcotic requirement, and side effects were compared between the groups for 48 hours postoperatively.

Results: Thirty patients completed the study (N = 15 in each group). No difference in pain scores at rest and movement was noted between the groups (P > 0.05). Patients in ketamine group received 40.42 ± 32.86 mg IV hydromorphone at 48 hours compared with 38.24 ± 26.19 mg in saline group (P = 0.84). Central nervous system side effects were observed in five (33%) ketamine group patients compared with nine (60%) in saline group (P = 0.29).

Conclusion: The addition of IV very low dose ketamine infusion regimen did not improve postoperative analgesia. Side effects were not increased with low dose ketamine.