Hemodynamic Mechanisms of Pressure Responsiveness and Performance of Traditional Predictors During Kidney Transplantation

<title>Abstract</title> <p> <bold>Background</bold> Fluid responsiveness does not necessarily result in pressure responsiveness. Although stroke volume variation and dynamic arterial elastance are commonly used to predict fluid responsiveness and pressure responsiveness, respectively, their performance during kidney transplantation is uncertain. The mechanisms by which fluid administration generate clinically meaningful increases in mean arterial pressure (MAP) in this population also remain poorly understood. <bold>Methods</bold> We performed a retrospective physiologic cohort study of fluid responsiveness testing (FRT) during episodes of intraoperative hemodynamic decompensation (MAP &lt; 75 mmHg) in kidney transplant recipients. Standardized FRT consisted of 250 mL crystalloid administered over 5 minutes. Fluid responsiveness was defined as a ≥ 10% increase in stroke volume, and pressure responsiveness as a ≥ 15% increase in MAP. Baseline stroke volume variation (SVV) and dynamic arterial elastance (EaDyn) were evaluated for association with fluid responsiveness and successful flow–pressure coupling (FPC), respectively. Hemodynamic mechanisms of pressure generation were assessed using baseline and post-FRT changes in arterial load variables. <bold>Results</bold> Sixty decompensated FRTs were analyzed in 40 recipients. Thirty-four tests (56.7%) were fluid responsive and 21 (35.0%) were pressure responsive. SVV demonstrated modest discrimination of fluid responsiveness (AUC 0.629), whereas EaDyn did not distinguish FPC from flow-responsive-only responses (AUC 0.516). Among pressure-responsive tests, 14 (66.7%) were pressure-responsive only and 7 (33.3%) achieved FPC. Compared with FPC, PR-only responses demonstrated larger increases in effective arterial elastance (ΔEa; +27.4% vs + 4.5%, p = 0.020) and a trend toward larger increases in systemic vascular resistance index (ΔSVRI; +25.0% vs + 5.8%, p = 0.056). <bold>Conclusions</bold> SVV and EaDyn demonstrated limited predictive performance during fluid responsiveness testing in kidney transplant recipients. Pressure responsiveness occurred through distinct hemodynamic pathways that may reflect the heterogeneous cardiovascular manifestations of end-stage renal disease. </p>