244ASSOCIATION BETWEEN SURGICAL PLETH INDEX AND STRESS HORMONES DURING GENERAL ANESTHESIASurgical nociceptive stimulation can adversely affect patient outcomes by increasing infection rates, hospital stay durations, and healthcare costs. The Surgical Pleth Index (SPI), which utilises normalised heart rate and pulse wave amplitude, offers a novel approach to quantifying nociception during general anaesthesia. However, its relationship with stress hormone dynamics and its efficacy in guiding intraoperative analgesia remain underexplored. Objective: This study aimed to evaluate the correlation between SPI and intraoperative stress hormone levels, assess its effectiveness in monitoring nociception, and compare its performance with traditional indicators such as blood pressure, heart rate, and BIS. Methods: A prospective, randomised, single-blinded study was conducted with 100 patients (ASA physical status I-II) undergoing elective ENT surgeries. Participants were randomised into two groups: SPI-guided remifentanil titration or standard criteria for analgesia. Stress hormone levels (ACTH, cortisol, epinephrine, and norepinephrine) were analysed at four event-specific time points. SPI values were recorded every 10 seconds. Statistical analyses included t-tests, ANOVA, and ROC curve evaluations. Results: SPI showed no significant correlation with stress hormones at baseline but demonstrated moderate-to-strong correlations during intubation, maximum stress, and post-maximum stress. SPI outperformed traditional indicators in detecting nociceptive stimulation and accurately predicted ACTH levels. Stress hormone dynamics reflected the severity of nociceptive stimulation, with ACTH and cortisol levels increasing significantly during maximum stress, while epinephrine and norepinephrine remained relatively stable. Conclusion: SPI is a reliable tool for monitoring nociception and intraoperative stress during general anaesthesia. It provides real-time, objective assessments of nociceptive stimulation and correlates well with stress hormone dynamics. Despite the promising results, further studies involving diverse surgical procedures are warranted to validate its clinical utility. SPI-guided anaesthesia has the potential to enhance patient management by improving intraoperative haemodynamic stability and reducing stress responses.Samala@gmail.comResearch1322023 Surgical Pleth Index (SPI), General anesthesia, Stress hormones, Target-controlled infusion, Elective surgery.Dr. Badrinath P,Dr. Chaitanya S,Dr. Ali Pasha MDAssistant Professor, Department of Anaesthesiology, Sri Lakshmi Narayana Institute of Medical Sciences & Hospital, Puducherry - 605 502, India,Associate Professor, Department of Anaesthesiology, SVS Medical College, Yenugonda, Mahbubnagar, Telangana 509001, India.,Assistant Professor, Department of Anaesthesiology, SVS Medical College, Yenugonda, Mahbubnagar, Telangana 509001, India