The Effect of Ketamine on Post-Operative Delirium and Analgesia in Patients Undergoing Orthopedic Surgery

Abstract

Background: Post-operative delirium and inadequate pain control remain major challenges in patients undergoing orthopedic surgery. Ketamine, an NMDA receptor antagonist, may have both neuroprotective and analgesic properties that could reduce delirium risk and opioid requirements.

Objective: To evaluate the effect of perioperative ketamine on the prevalence of postoperative delirium and analgesic outcomes in patients undergoing orthopedic surgery.

Methods: A total of 220 adult patients scheduled for elective orthopedic procedures were distributed into two equal groups: ketamine (n=110) and control/placebo (n=110). Demographic and perioperative variables were recorded. The primary outcome was the incidence of postoperative delirium within 72 hours, assessed using the Confusion Assessment Method (CAM). Secondary outcomes included pain scores, opioid consumption, and adverse events during the first 24 hours post-surgery. Data were analyzed using chi-square and t-tests, and predictors of delirium were identified through logistic regression analysis.

Results: Both groups were demographically comparable (mean age 56 ± 12 years; 54.5% male). Post-operative delirium occurred significantly less frequently in the ketamine group (9.1%) than in the control group (20.0%; p = 0.035), with a shorter duration of delirium (22 ± 10 vs 35 ± 16 hours; p = 0.01). Patients receiving ketamine reported lower pain scores in the PACU and at 24 hours (p < 0.001), required less opioid analgesia (18 ± 12 vs 28 ± 15 mg morphine equivalents; p < 0.001), and had a longer time to first analgesic request (p < 0.001). Mild hallucinations were more frequent in the ketamine group (7.3% vs 0.9%; p = 0.035), but no increase in serious adverse events was observed. In multivariate logistic regression, ketamine use remained independently protective against delirium (adjusted OR = 0.38; 95% CI 0.16–0.88; p = 0.024), while age ≥ 65 years and preoperative cognitive impairment were independent risk factors.

Conclusion: Perioperative ketamine significantly reduced the incidence and duration of post-operative delirium and improved analgesic outcomes in patients undergoing orthopedic surgery, without increasing serious adverse events. These findings suggest that low-dose ketamine may serve as a valuable adjunct to multimodal anesthesia for improving post-operative recovery in orthopedic patients.