Perfusion Index as a Predictor of Hypotension Following Spinal Anesthesia in Below-Umbilical Surgeries.

Background Hypotension following spinal anesthesia is common and may adversely affect end-organ perfusion. Perfusion index (PI), derived non-invasively from pulse oximetry, reflects peripheral vascular tone and may help identify patients at risk of post-spinal hypotension. This study aimed to determine the diagnostic threshold of baseline PI for predicting hypotension following spinal anesthesia in adults undergoing elective below-umbilical surgery and to assess its diagnostic performance. Methods This prospective observational diagnostic accuracy study included adult patients aged 18-65 years with the American Society of Anesthesiologists physical status I or II undergoing elective below-umbilical surgery under spinal anesthesia. Baseline PI, heart rate, and blood pressure were recorded before spinal anesthesia, followed by serial hemodynamic and PI measurements for 30 minutes. Hypotension was defined as a decrease in mean arterial pressure of >20% from baseline. Receiver operating characteristic analysis was performed to determine the optimal baseline PI cut-off using Youden's index, with an estimation of sensitivity, specificity, predictive values, and accuracy. Results A total of 92 patients were analyzed, of whom 21 (22.8%) developed post-spinal hypotension. Baseline PI was significantly higher among patients who developed hypotension than among those who did not (4.38±1.67 vs. 1.51±0.53, P<0.001). Baseline PI demonstrated excellent discriminatory ability, with an area under the receiver operating characteristic curve of 0.999 (95% confidence interval: 0.995-1.000, P<0.001). A baseline PI of ≥2.53 yielded 100% sensitivity, 98.6% specificity, 95.2% positive predictive value, 100% negative predictive value, and 98.9% overall accuracy. Conclusion Baseline PI demonstrated excellent diagnostic performance for predicting post-spinal hypotension in adults undergoing elective below-umbilical surgery. A baseline PI of ≥2.53 may help identify patients at increased risk and facilitate anticipatory hemodynamic management.