Comparison of Postoperative Pain Scores between Intraoperative Intravenous Ketamine and Placebo in Patients Undergoing Unilateral Total Knee Arthroplasty under General Anesthesia: a Double-blind Randomized Controlled Trial

Abstract

Background: Multimodal analgesia with intra-operative intravenous ketamine for acute postoperative pain control has been reported to be effective. Research on subanesthetic ketamine for total knee arthroplasty (TKA) under general anesthesia (GA) is limited. We hypothesize that intraoperative intravenous ketamine may help reduce postoperative pain and opioid consumption in patients undergoing unilateral TKA with GA . Methods: This study was a prospective, single-center, double-blind randomized controlled trial. The 100 patients who underwent TKA under GA were randomly divided into two groups. One group received intraoperative intravenous ketamine, administered as a bolus dose of 0.5 mg/kg followed by a continuous infusion at 0.25 mg/kg/h until the end of surgery, while the control group received a placebo. The primary outcome measure was postoperative pain. The secondary outcomes included morphine consumption, the timing of intravenous analgesia requests, the length of hospital stay, and complications. Results: There were no significant differences between the two groups in terms of postoperative numerical rating scale scores for resting and movement pain at 24 h postoperative morphine consumption, the duration of intravenous analgesic requests, the length of hospital stay, and complications. Conclusion: Intraoperative intravenous ketamine in patients undergoing TKA under GA did not reduce 24-h postoperative pain scores at rest or during movement, nor did it decrease morphine consumption. Additionally, it did not shorten the length of hospital stay, delay the timing of the first analgesic request, or affect complication rates.