331EVALUATING THE SURGICAL PLETH INDEX FOR NOCICEPTION MONITORING: CORRELATION WITH STRESS HORMONES DURING GENERAL ANAESTHESIAEffective monitoring of nociception during general anaesthesia is critical for optimising analgesia and minimising intraoperative stress responses. The Surgical Pleth Index (SPI), which assesses nociceptive responses based on pulse wave amplitude and heart rate variability, has been proposed as a useful tool for guiding analgesic administration. This prospective, randomised, single-blinded study evaluated SPI's effectiveness in 160 patients undergoing elective ENT surgery, comparing it with conventional nociceptive indicators. Stress hormone levels (ACTH, cortisol, epinephrine, and norepinephrine) were used as biological markers of nociception. Findings revealed moderate-to-strong correlations between SPI and stress hormone fluctuations, particularly during intubation, maximal surgical stimulation, and post-maximal stimulation. While SPI showed promise in predicting intraoperative stress, its accuracy varied across different states of consciousness. Further research is needed to refine SPI's application and explore its role across various surgical settings to enhance anaesthetic management and patient outcomes.Nikhil@gmail.comResearch922019 Surgical Pleth Index, Nociception Monitoring, Stress Hormones, Anaesthesia, Pain ManagementDr. Nikhil ChandrasekarAssistant Professor, Department of Anaesthesiology, Sree Balaji Medical College & Hospital, Chennai – 600044, Tamil Nadu, India.