Perfusion index and risk of hypotension after spinal anesthesia in lower abdominal surgery: Insights from a prospective observational study

Background: Hypotension following spinal anesthesia is a common complication during lower abdominal surgeries and may result in significant organ hypoperfusion. Early identification of patients at risk remains challenging. The perfusion index (PI), derived non-invasively from pulse oximetry, reflects peripheral vascular tone and may predict post-spinal hypotension. Aims and Objectives: This study aimed to evaluate whether baseline lower limb PI can predict intraoperative hypotension following spinal anesthesia. Materials and Methods: The current study enrolled 100 adult patients (18–60 years, American Society of Anesthesiologists I–II) scheduled for elective procedures. Lower abdominal surgery under spinal anesthesia at our tertiary care hospital. Baseline PI was measured at the second toe using a pulse oximeter before the subarachnoid block. Patients were stratified into two groups based on PI (≥2 vs. <2). Standard spinal anesthesia with hyperbaric bupivacaine was administered, and hemodynamic parameters were recorded at predefined intervals. Hypotension was defined as mean arterial pressure <65 mmHg occurring at least once intraoperatively. Sensitivity, specificity, predictive values, and receiver operating characteristic (ROC) analysis were performed. Results: Hypotension was observed among 52 patients. A significantly higher incidence of hypotension was observed in patients with a baseline of PI ≥2 compared to those with PI <2 (66.1% vs. 28.9%, P<0.001). Baseline PI ≥2 predicted hypotension in patients with a sensitivity of 78.8%, specificity of 56.3%, positive predictive value of 66.1%, and negative predictive value of 71.1%. ROC analysis also demonstrated an area under the curve of 0.73 (95% confidence interval: 0.63–0.83). Conclusion: Baseline lower limb PI ≥2 is a useful non-invasive predictor of hypotension following spinal anesthesia in lower abdominal surgeries. Routine PI assessment may aid in early risk stratification and proactive hemodynamic management.