Evolution of Tissue Perfusion and Venous Congestion Markers in Fluid-Responsive Septic Shock Patients

Septic shock remains a leading cause of mortality in intensive care, and while fluid resuscitation (FR) is a cornerstone of early management, its benefit-risk balance is highly variable. Excessive fluid administration can cause venous congestion and organ dysfunction, while insufficient resuscitation risks hypoperfusion. Current strategies often rely on fluid responsiveness (i.e., increased cardiac output after fluids), but this does not guarantee improved outcomes, particularly if congestion ensues. This prospective, multicenter, observational study aims to assess the clinical impact of FR in septic shock patients who are fluid responsive. The primary objective is to evaluate changes in tissue perfusion and venous congestion markers following FR. Patients will be categorized into four response profiles based on the presence or absence of perfusion improvement and congestion worsening. Secondary objectives include exploring the prognostic implications of each profile (organ dysfunction, mortality), identifying pre-FR predictors of adverse responses, evaluating changes in congestion markers after passive leg raising (PLR), and performing phenotypic clustering and mediation analyses. Eligible patients are adults with septic shock requiring vasopressors and mechanical ventilation, with confirmed fluid responsiveness via echocardiography. Each patient will undergo standardized pre- and post-FR assessments, including cardiac ultrasound, Doppler of hepatic/portal veins (VeXUS), CVP, perfusion markers, and blood gases. Data on SOFA scores, organ support duration, and 28-day mortality will be collected. Approximately 170 patients will be enrolled across five ICUs experienced in advanced hemodynamic monitoring. Statistical analyses will include multivariate modeling, clustering, ROC curves, and mediation analyses. By identifying phenotypes of fluid-responsive but fluid-intolerant patients, the study aims to refine fluid management strategies and improve outcomes through