Tehran University of Medical Sciences Archives of Anesthesiology and Critical Care 2423-5849 0 0 2026 05 11 Comparison of Opioid-Free and Opioid-Based Anesthesia Techniques on qNOX Index in Abdominal Surgery under General Anesthesia 1530 1530 Muhammad Rahman E. Nasution Study Program of Anesthesiology and Intensive Care, Faculty of Medicine, Adam Malik Hospital, Universitas Sumatera Utara, Medan, Indonesia. Andriamuri Primaputra Lubis Department of Anesthesiology and Intensive Care, Faculty of Medicine, Universitas Sumatera Utara, Adam Malik Hospital, Medan, Indonesia. Muhammad Arshad Department of Anesthesiology and Intensive Care, Faculty of Medicine, Universitas Sumatera Utara, Adam Malik Hospital, Medan, Indonesia. Putri Eyanoer Department of Community and Preventive Medicine, Faculty of Medicine, Universitas Sumatera Utara, Medan, Indonesia. 2025 12 19 2025 12 25 Background: Opioid-Free Anesthesia (OFA) is a multimodal approach designed to avoid intraoperative opioid use, aiming to reduce side effects such as respiratory depression, nausea, vomiting, and postoperative dependency. This study aimed to compare the effectiveness of OFA and Opioid-Based Anesthesia (OBA) on the qNOX index during abdominal surgery under general anesthesia. Methods: This randomized double-blind controlled trial involved 42 adult patients undergoing elective abdominal surgery under general anesthesia in three hospitals in Medan. Subjects were assigned to two groups: OFA (ketamine, lidocaine, and dexmedetomidine combination) and OBA (fentanyl-based). The qNOX index was measured using the CONOX® monitor at five time points: before induction, during intubation, before incision, during incision, and one hour after incision. Data were analyzed using an independent t-test and a chi-square test. Results: No significant difference in qNOX values was observed between groups at any time point (p>0.05). Both groups maintained comparable intraoperative hemodynamic stability. Conclusion: Opioid-free anesthesia provides comparable nociceptive control and hemodynamic stability to opioid-based anesthesia. OFA represents a safe and effective alternative for abdominal surgery under general anesthesia. https://aacc.tums.ac.ir/index.php/aacc/article/view/1530