Pre-anesthetic Ultrasonography of the Subclavian Vein and Inferior Vena Cava for Predicting Hypotension After General Anesthesia Induction in Patients Undergoing Abdominopelvic Surgeries: A Prospective Observational Study

Background: Post-induction hypotension (PIH) jeopardizes vital organ perfusion and is associated with perioperative morbidity and mortality. This study aimed to evaluate and compare the diagnostic accuracy of preoperative ultrasonography (USG) measurement of the inferior vena cava (IVC) and subclavian vein (SCV) for predicting PIH following induction of general anesthesia (GA) in patients undergoing abdominopelvic surgeries. Methods: A prospective observational study was conducted on 57 patients of North Indian ethnicity undergoing elective abdominopelvic surgeries. IVC and SCV diameters and collapsibility index (CI) were measured using USG before induction of GA. The study focused on comparing these measurements with the incidence of PIH. Results: The IVC-CI (p <0.001), SCV-CI (p <0.001), and the minimum diameter of the IVC (p = 0.008) were significant predictors of PIH. The optimal cut-off values for predicting PIH were 27.91% and 35.59% for IVC-CI and SCV-CI, respectively. SCV-CI exhibited diagnostic accuracy comparable to that of IVC-CI in predicting PIH, demonstrating higher specificity (97% vs. 90.3%) but marginally lower sensitivity (69.2% vs. 73.1%). The time taken to measure USG-guided SCV parameters was significantly less compared to that of IVC (111.58± 25.91 vs. 155.91 ± 35.77 seconds; p < 0.001). No significant correlations were found between PIH and the maximum IVC or maximum or minimum SCV diameters. Conclusion: IVC-CI and SCV-CI showed comparable diagnostic accuracy in predicting PIH under a standardized induction protocol. Early identification of high-risk patients may enable anticipatory hemodynamic management. SCV visualization and assessment were faster than IVC, making SCV-CI a practical alternative when IVC imaging is challenging or when rapid evaluation is needed, although multicenter studies are needed for validation.