ANI-Guided vs. Standard Remifentanil Dosing in Spine Surgery: A Randomized Controlled Trial

Background Effective intraoperative pain management is essential for maintaining anaesthetic depth and hemodynamic stability and improving postoperative outcomes. The Analgesia Nociception Index (ANI) provides continuous, noninvasive feedback on autonomic tone and nociceptive balance, potentially enabling more precise opioid titration. Methods In this assessor-blinded, randomized controlled trial, 58 adult patients who underwent elective lumbar spine surgery were allocated to either ANI-guided analgesia or standard analgesia. Remifentanil was titrated to maintain ANI values between 50–70 in the intervention group. Data from 54 patients were analysed after exclusions. The primary outcome was total intraoperative remifentanil consumption. The secondary outcomes included the postoperative pain score (VAS), incidence of nausea and vomiting (PONV), and patient satisfaction. Results The mean remifentanil use was significantly lower in the ANI group (636.9 ± 90.3 µg) than in the control group (993.1 ± 146.2 µg; p < 0.001). VAS scores at 10, 20, 30, and 60 minutes were consistently lower in the ANI group (p < 0.001). The incidence of PONV was lower (6.9% vs. 27.6%; p = 0.037), and the satisfaction scores were higher (p = 0.011). Conclusions ANI-guided remifentanil administration improves intraoperative opioid precision, reduces postoperative pain and nausea, and enhances patient satisfaction. Trial Registration: The study protocol was registered prospectively in the Iranian Registry of Clinical Trials (IRCT20180303038923N1).