Intraoperative remifentanil administration guided by nociception level index (NOL) in patients undergoing hip surgery under general anesthesia

Objective: The aim of this study was to investigate the effects of intraoperative remifentanil administration guided by the Nociception Level (NOL) Index on opioid consumption and postoperative pain management in patients undergoing hip surgery under general anesthesia. In addition, the impact of NOL guidance on postoperative morphine consumption, hemodynamic stability, and complications was evaluated. Methods: This prospective, single-center, randomized study included a total of 60 patients with ASA physical status I–III who underwent hip surgery. Patients were randomly assigned to the NOL group (n=30) and the control group (n=30). In the NOL group, intraoperative remifentanil infusion was titrated to maintain NOL values between 10 and 25. In the control group, opioid management was performed based on standard clinical parameters. Intraoperative remifentanil consumption, hemodynamic data, postoperative pain scores (NRS), and morphine consumption were evaluated. Results: There were no significant differences between the two groups in terms of demographic or clinical characteristics. Although intraoperative remifentanil consumption was lower in the NOL group, this difference did not reach statistical significance (1160 µg vs. 1200 µg, p=0.165). Postoperative NRS pain scores and PCA morphine consumption were also similar (22 mg vs. 19 mg, p=0.276). Hemodynamic parameters, respiratory values, and sevoflurane MAC levels showed no significant differences between groups. Although previous studies have reported that the NOL index may reduce opioid consumption and postoperative pain scores, comparable clinical outcomes were observed in this study. Conclusion: Analgesia management guided by the NOL index in patients undergoing hip surgery was found to be safe and feasible but did not demonstrate a significant advantage over standard methods. These findings suggest that the NOL index may serve as a potential tool for intraoperative opioid titration. However, multicenter randomized controlled trials with larger sample sizes and different surgical populations are needed to more clearly demonstrate its effectiveness. Keywords: Nociception Level Index (NOL), Remifentanil, Hip Surgery, Postoperative Pain