Study on the correlation between changes in perfusion index under different body positions and the risk of hypotension after anesthetic induction

Post-induction hypotension (PIH) is a common complication during general anesthesia. Perfusion index (PI), a non-invasive indicator reflecting peripheral tissue perfusion and hemodynamic status, has shown potential predictive value for PIH. We hypothesized that the change of PI ($$\Delta $$PI) between supine and 45° semi-recumbent positions can predict PIH in patients undergoing elective general anesthesia, and a cut-off value of $$\Delta $$PI for identifying a higher risk of PIH can be determined. This prospective observational study enrolled eligible adults with American Society of Anesthesiologists (ASA) physical status I–III undergoing elective surgery under general anesthesia. Before anesthesia induction, the PI of each patient was recorded after a period of supine rest to achieve hemodynamic stability; subsequently, PI was measured again after achieving stability in the 45° semi-recumbent position. $$\Delta $$PI between the two positions was calculated for analysis. PIH was defined as systolic blood pressure (SBP) $$<90$$ mmHg, mean arterial pressure (MAP) $$<65$$ mmHg, or a reduction in MAP by $$>30\%$$ from baseline within 15 minutes after anesthesia induction. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the predictive value of $$\Delta $$PI for PIH, including calculation of the area under the curve (AUC), optimal cut-off value, sensitivity, and specificity. Data from 96 patients were analyzed. After anesthesia induction, 51 patients (53.1%) developed PIH. The AUC of $$\Delta $$PI for predicting PIH was 0.824 (95% CI: 0.741–0.908). The optimal cut-off value of $$\Delta $$PI was 22.0%, which yielded a sensitivity of 72.5% and a specificity of 86.7%. This study was registered in the Clinical Trial Registry of China on 17/12/2024 (ChiCTR2400094135). The $$\Delta $$PI between supine and 45° semi-recumbent positions was a reliable predictor of post-induction hypotension after general anesthesia induction, wherein $$\Delta $$PI greater than 22.0% was the threshold.