243ASSOCIATION BETWEEN SURGICAL PLETH INDEX AND STRESS HORMONE LEVELS DURING GENERAL ANAESTHESIAThis prospective, randomised, single-blinded study evaluated the correlation between the Surgical Pleth Index (SPI) and stress hormone levels during general anaesthesia in 80 ASA I-II patients undergoing elective ear, nose, and throat (ENT) surgery. Patients were divided into an SPI group, where remifentanil titration was guided by SPI values, and a Control group, where conventional criteria determined anaesthetic adjustments. Stress hormone levels, including ACTH, cortisol, epinephrine, and norepinephrine, were measured at four event-related time points using blood samples analysed via high-performance liquid chromatography. The study revealed moderate-to-good correlations between SPI and stress hormones during nociceptive stimulation events (e.g., intubation, surgical incision). SPI values were particularly effective at predicting ACTH levels (AUC 0.85), with a threshold value of SPI 46 showing 81% sensitivity and 73% specificity. Cortisol, epinephrine, and norepinephrine were less reliably predicted by SPI. Stress hormone levels were highest preoperatively and decreased significantly post-surgery. SPI demonstrated superior performance compared to traditional measures such as blood pressure and heart rate in monitoring intraoperative stress and nociception. However, SPI was not correlated with stress hormone levels when patients were conscious. These findings suggest that SPI is a promising tool for assessing nociception and optimising analgesia during general anaesthesia, particularly in surgical settings.gouni@gmail.comResearch1222022Surgical Pleth Index (SPI), Stress Hormones, General Anaesthesia, Nociception MonitoringDr. Gouni Uday KumarAssociate Professor, Department of Anaesthesiology, Mamata Medical College Netaji Nagar, Rotary Nagar, Khammam, Telangana 507002, India.