Tehran University of Medical Sciences Archives of Anesthesiology and Critical Care 2423-5849 0 0 2026 08 01 1628 1628 Alireza Shakeri Department of Anesthesiology, Imam Hossein Hospital, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Arezou Ashari Department of Community Medicine, Imam Hossein Hospital, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Zahraa Hasan Mohammed Mohammed Department of Anesthesiology, Imam Hossein Hospital, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Ebtehaj Heshmatkhah Department of Obstetrics and Gynecology, Valiasr Private Hospital, Qom, Iran. Niloofar Khosravi Pain Research Center, Department of Anesthesiology and Pain Medicine , School of Medicine, Iran University of Medical Sciences, Tehran, Iran. Dariush Abtahi Department of Anesthesiology, Imam Hossein Hospital, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran. 2026 04 30 2026 05 04 Background: Post-spinal shivering is a common complication during cesarean delivery under spinal anesthesia, occurring in 30-50% of parturients. Shivering increases oxygen consumption, interferes with monitoring, and negatively impacts maternal satisfaction. Intrathecal ketamine, an NMDA receptor antagonist, may provide anti-shivering benefits while avoiding systemic side effects. The objective is to evaluate the efficacy and safety of intrathecal ketamine (0.1 mg/kg) combined with bupivacaine in reducing post-spinal shivering during elective cesarean sections. Methods: This parallel-group, double-blind, randomized clinical trial enrolled 100 ASA II parturients undergoing elective cesarean section under spinal anesthesia. Patients were randomized to receive either intrathecal bupivacaine 12.5 mg plus ketamine 0.1 mg/kg (Group A, n=50) or bupivacaine 12.5 mg alone (Group B, n=50). Primary outcomes included shivering incidence and severity using the Bedside Shivering Assessment Scale. Secondary outcomes included block characteristics, time to the first analgesic request, and adverse events. Results: Intraoperative shivering was significantly reduced in the ketamine group (10% vs. 40%; p<0.001; OR=0.167, 95% CI: 0.056–0.492), representing an 83% relative risk reduction. Time to first analgesic request was prolonged in Group A (145 vs. 125 minutes; p<0.001). Motor block duration, PONV incidence, and patient satisfaction were comparable between groups. No neurological complications were observed during the two-month follow-up. Conclusion: Intrathecal ketamine (0.1 mg/kg) significantly reduces post-spinal shivering incidence and severity while prolonging postoperative analgesia without increasing adverse effects, representing an effective non-opioid adjuvant for obstetric spinal anesthesia. https://aacc.tums.ac.ir/index.php/aacc/article/view/1628