Abstract
BACKGROUND: Postoperative pain control after total knee arthroplasty (TKA) remains challenging. Intraoperative dexmedetomidine and ketamine are commonly used in multimodal analgesia to reduce pain and opioid requirements. This study aimed to compare their effects on opioid consumption, pain, hemodynamics and satisfaction. MATERIALS AND METHODS: This prospective, randomized, double-blind study included 104 adults (≥ 18 years) with ASA I-III status undergoing TKA under spinal anesthesia. After all patients had received spinal anesthesia, they were randomized into two equal groups (n = 52). Group D received dexmedetomidine (1 µg/kg loading dose, then 0.5 µg/kg/h); Group K received ketamine (0.1 mg/kg/h without a loading dose). Sedation level was titrated to achieve a modified Observer's Assessment of Alertness/Sedation (OAA/S) score of 3-4. Postoperatively, a single-shot femoral nerve block was administered to all patients. Primary outcome was total opioid consumption in 24 h. Secondary outcomes included Visual Analog Scale (VAS) scores, hemodynamic parameters, side effects and patient satisfaction. RESULTS: Tramadol use in 24 h was similar (Group D: 175.29 ± 44.62 mg; Group K: 155 ± 44.48 mg; p = 0.44). VAS scores were comparable at all time points. Time to ambulation was longer in the ketamine group (Group D: 4.4 ± 1.4 h; Group K: 5.3 ± 2.5 h; p = 0.04). Group D showed significantly lower heart rate and blood pressure values at multiple time points (p < 0.001). Patient satisfaction was high in both groups and no hypotension or bradycardia occurred in any group. CONCLUSION: Although no significant differences were found between dexmedetomidine and ketamine, both agents provided comparable analgesia and opioid consumption, supporting their potential role as adjuvants in multimodal analgesia for patients undergoing TKA. TRIAL REGISTRATION: ISRCTN11906298, retrospectively registered on 13.06.2025.