Tehran University of Medical Sciences Archives of Anesthesiology and Critical Care 2423-5849 0 0 2026 06 01 1595 1595 Mohammad Golparvar Department of Anesthesiology and Critical Care, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran. Sahand Golparvar Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran. Melika Foroughi Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran. 2026 02 27 2026 04 23 Background: Spinal anesthesia is a commonly used technique in modern anesthetic practice and is frequently associated with hypotension, a complication that is more pronounced in patients with hypovolemia. Early identification of patients at risk for hypotension is essential in anesthetic management and may reduce anesthesia‑related surgical complications. This study aimed to predict hypotensive events during surgery by evaluating the relationship between changes in the inferior vena cava (IVC) diameter following a passive leg raising (PLR) maneuver. Methods: This observational cohort study was conducted on 100 patients undergoing surgery under spinal anesthesia. The diameter of the IVC was measured using ultrasonography before and after performing a PLR maneuver. Hemodynamic parameters, including heart rate, blood pressure, body temperature, and oxygen saturation, were recorded. In addition, the relationships between changes in IVC diameter and intraoperative fluid intake, bleeding, administration of sedative and vasopressor medications, and the occurrence of hypotension, hypertension, bradycardia, and tachycardia during the first 90 minutes of surgery were evaluated. Results: The findings demonstrated a significant correlation between changes in the IVC diameter and systolic blood pressure, as well as with the incidence of hypotension and hypertension during surgery. The mean diameter of the IVC increased significantly following the PLR maneuver. The mean change in systolic blood pressure during surgery compared with the preoperative baseline was +14.80 mmHg. Correlation analysis revealed a significant association between changes in IVC diameter and systolic blood pressure (p = 0.009), as well as with the occurrence of hypotension and hypertension (p = 0.001 and p = 0.004, respectively). Conclusion: This study provides evidence that changes in IVC diameter may serve as an indicator of alterations in systolic blood pressure and the occurrence of hypotension and hypertension during surgery under spinal anesthesia. Nevertheless, further studies are required to validate these findings and clarify their clinical implications. The results of this study suggest that assessment of IVC diameter changes may contribute to improved perioperative monitoring and patient management in procedures performed under spinal anesthesia. https://aacc.tums.ac.ir/index.php/aacc/article/view/1595