Oral ketamine for acute postoperative analgesia (OKAPA) trial: A randomized controlled, single center pilot study.

Study objective: Although opioids represent the mainstay of treating surgical pain, their use is associated with significant side effects. There is an urgent need to find new pain relievers with safer side effect profiles. One drug that has been receiving increasing attention is ketamine. By using the oral route of administration, ketamine could potentially be used by patients in a less resource-intensive manner with similar efficacy. This study aims to examine the role of oral ketamine in improving recovery after major spine surgery.

Design: A prospective, single-center, double blinded parallel arm, placebo controlled randomized feasibility trial.

Setting: Toronto Western Hospital (TWH), UHN, Toronto, Canada.

Patients: Adult patients (aged 18-75) undergoing multi-level lumbar spine decompression and fusion with planned overnight admission in hospital.

Interventions: Study treatment (oral ketamine 30 mg) or matching placebo for three days (nine doses total) or until hospital discharge.

Measurements: The primary outcome was the patient-reported Quality of Recovery-15 score (QoR-15). Secondary outcomes were opioid use, pain intensity, pain interference (PROMIS-pain interference questionnaire), mood (PHQ-9) and, side-effects (Generic Assessment of Side Effects Scale).

Main results: Data from 35 patients were analyzed, of which 18 patients in the ketamine group and 17 patients in the placebo group. There were no significant differences identified in QoR-15 scores at postoperative days 1,3,7, and 30. There were also no significant differences found in pain intensity scale scores at postoperative days 1, 3, 7, and 30, and PROMIS and PHQ-9 scores at postoperative days 7 and 30. Significantly less oral opioids were used in the ketamine group compared to the placebo group on postoperative day 3 and by postoperative day 7. In addition, patients in the ketamine group spent significantly less days on oral opioids and trended to be discharged from hospital earlier.

Conclusion: This pilot study demonstrated that low dose oral ketamine can be safely used as an adjunct in postoperative pain treatment to help reduce opioid consumption after major spine surgery.