Comparison of Postoperative Nociception Between NOL-guided and Standard Intraoperative Analgesia Based on Fentanyl

Methodology: In this RCT double-blinded study will invite to 100 patients aged between 18 and 50 years admitted for elective surgery that is planned to require general anesthesia, with fentanyl as the opioid of choice for intraoperative analgesia. Each patient will be randomly allocated to one of two groups: the intervention group will be provided intraoperative analgesia guided by NOL values (n=50), and the control group will be provided standard intraoperative analgesia (n=50). To account for inter-personal variability, the NOL threshold value associated with nociceptive stimulation will be assessed on each patient at baseline condition with the Quantitative Sensory Testing (QST) and neuroinflammatory mediators MCP-1, IL-1, IL-1b, and IL-10 will be measured pre- and post-surgery in both groups. Opioid consumption and AVS will be assessed during the stay at the post-surgical care unit as a measurement of post-operative pain and will follow them until three months after surgery. Statistical Analysis: Results will be expressed as means (±SD) or numbers (%). When indicated, 95% confidence interval (CI) will be calculated. A p-value \< 0.05 will be considered statistically significant. Differences between groups on post-surgical opioid consumption, Δz-score of QST measurements, and serum biomarkers level will be analyzed with Student's T-test for unpaired samples. For analysis purposes, VAS scores will be grouped into three distinct categories: Mild (0-3), Moderate (4-6) and Severe (7-10) pain. Differences between groups will be analyzed with Chi-square test.