Dynamic Arterial Elastance as a Predictor of Intraoperative Fluid Responsiveness in Elderly Patient over 70 Years of Age Undergoing Spine Surgery in the Prone Position Under General Anesthesia: A Validation Study

<b>Background</b>: Optimizing fluid therapy is critical for maintaining hemodynamic stability in elderly patients undergoing major surgeries. Dynamic arterial elastance (Eadyn), defined as the ratio of pulse pressure variation (PPV) to stroke volume variation (SVV), has been proposed as a predictor of fluid responsiveness, especially in challenging conditions like prone-positioned spine surgery under general anesthesia. <b>Methods:</b> Hemodynamic parameters were measured before and after fluid loading with 500 mL of crystalloid solution. Patients were classified as responders or non-responders based on a ≥15% increase in mean arterial pressure (MAP) post-fluid administration. Predictive performance of these parameters was assessed using receiver operating characteristic (ROC) analysis. <b>Results:</b> Of the 37 patients, 15 were classified as responders and 22 as non-responders. Eadyn demonstrated poor predictive performance (AUC = 0.508). In contrast, SVV (AUC = 0.808), PPV (AUC = 0.738), and C (AUC = 0.741) exhibited moderate to high predictive ability. Responders exhibited significantly higher baseline SVV, PPV, and net arterial compliance compared to non-responders. <b>Conclusions:</b> Dynamic arterial elastance (Eadyn) showed limited predictive ability for fluid responsiveness in elderly patients undergoing spine surgery in the prone position. In contrast, stroke volume variation (SVV), pulse pressure variation (PPV), and net arterial compliance (C) demonstrated superior reliability, with SVV emerging as the most accurate predictor.