Tehran University of Medical Sciences Archives of Anesthesiology and Critical Care 2423-5849 0 0 2026 06 27 1435 1435 Azim Honarmand Department of Anesthesiology and Critical Care, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran. Mohammadreza Safavi Department of Anesthesiology and Critical Care, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran. Atefeh Ghosouri Department of Anesthesiology and Critical Care, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran. Zahra Rahimi Department of Anesthesiology and Critical Care, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran. Nayere Hashemi Department of Anesthesiology and Critical Care, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran. 2025 10 02 2025 11 06 Background: Effective analgesia following upper limb orthopedic surgery reduces opioid consumption and enhances recovery. Ketamine demonstrates opioid-sparing and antihyperalgesic properties; however, the optimal low-dose regimen is not well established. This study compared two ketamine infusion regimens for their effects on postoperative pain outcomes. Methods: In this triple-blind, placebo-controlled randomized trial conducted at Kashani Educational and Medical Center in 2024, 93 adults aged 18–65 years with American Society of Anesthesiologists (ASA) physical status I–II undergoing upper limb orthopedic surgery under anesthesia were randomized into three groups. The low-dose group received ketamine 0.5 mg/kg followed by 0.25 mg/kg/h; the high-dose group received 0.75 mg/kg followed by 0.5 mg/kg/h; the control group received normal saline. Pain was assessed using a visual analog scale at 2, 4, 6, 12, and 24 hours postoperatively. Timing of rescue analgesic administration, total analgesic consumption, hemodynamic parameters, recovery variables, and patient satisfaction were recorded. Results: All 93 patients completed the study, with 31 participants in each group. Baseline characteristics were similar across groups. Both low- and high-dose ketamine groups demonstrated reduced total analgesic consumption compared to controls (0.64 ± 1.21 and 0.58 ± 1.14 vs 1.76 ± 2.08; P = 0.043). The time to first rescue analgesic request was significantly longer in the ketamine groups (317.25 ± 25.62 and 326.84 ± 36.28 vs 73.48 ± 20.71 minutes; P < 0.001). Patient satisfaction scores were higher in both ketamine groups (8.24 ± 2.09 and 8.35 ± 2.15 vs 5.82 ± 1.64; P < 0.001). Mean arterial pressure and heart rate varied over time and between groups. Conclusion: Intraoperative low-dose ketamine infusion reduced postoperative analgesic requirements and prolonged the time to rescue analgesia. The higher-dose regimen did not provide additional benefit. https://aacc.tums.ac.ir/index.php/aacc/article/view/1435