Perfusion Index as a Predictor of Spinal Anesthesia Success: A Time-dependent Receiver Operating Characteristic Curve Analysis
Year: 2026
Type: article
Abstract: Background: Traditional assessments of spinal anesthesia success, such as pinprick and temperature tests, are subjective and rely on patient cooperation, limiting their utility in sedated, pediatric, or uncooperative patients. Perfusion index (PI), a noninvasive parameter from pulse oximetry reflecting peripheral perfusion via the pulsatile-to-nonpulsatile blood flow ratio, may objectively indicate sympathetic blockade-induced vasodilation. Methods: In this prospective analytical study, 229 American Society of Anesthesiologists I–II patients aged 18–50 years undergoing elective surgeries under spinal anesthesia had PI, PI ratio (post-/preblock), mean arterial pressure (MAP), heart rate, and skin temperature measured at baseline and 2, 4, 6, 10, 15, and 30 min postblock. Block success was defined as bilateral pinprick sensory loss to T10 within 30 min. Time-dependent receiver operating characteristic curves were used to assess predictive accuracy. Results: Spinal anesthesia succeeded in 219/229 patients (95.6%). PI rose significantly from baseline (0.95 ± 0.31) to 30 min (9.46 ± 1.85; P < 0.001). Optimal cutoffs: 2-min PI >1.35 (sensitivity 96.3% and specificity 90%); 4-min PI >2.10 and PI ratio >1.5 (both 100% sensitivity/specificity). MAP fell (92.0 ± 4.2–75.5 ± 5.6 mmHg; P < 0.001), and skin temperature rose (28.4°C ± 0.9°C to 33.2°C ± 1.3°C; P < 0.001). Conclusion: PI and PI ratio provide early, objective prediction of spinal block success, outperforming subjective tests in challenging cases. Clinical adoption could streamline assessment.
Institution: Goa Medical College
Language: English
Subfield: Anesthesiology and Pain Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: diamond
OpenAlex ID: W7224123048