Right Ventriculo-Arterial Coupling During Fluid Loading in ICU Patients

Preload responsiveness and venous congestion have largely been investigated independently in recent literature. However, recent data report a similar incidence of venous congestion regardless of fluid responsiveness status, challenging the concept of a linear continuum between preload independence and fluid intolerance. These findings support the need for a more individualized hemodynamic management strategy that takes venous congestion risk into account. The right ventricle plays a central role in this framework. Its function is to maintain an adequate venous return pressure gradient to ensure cardiac output while limiting upstream venous congestion, under strong dependence on its afterload. In physiological conditions, the right ventricle adapts to changes in afterload by increasing contractility to preserve right ventriculo-arterial coupling and optimize its performance. In chronic cardiopulmonary diseases, right ventriculo-arterial uncoupling is a well-established prognostic factor, including the presence of occult uncoupling revealed by fluid loading. In critically ill patients, right ventricular systolic dysfunction associated with venous congestion-defining right heart failure-is strongly associated with increased mortality, as is right ventriculo-arterial uncoupling itself. To support the concept of fluid tolerance, the investigators hypothesize that impairment of right ventriculo-arterial coupling may exist or occur during fluid loading in critically ill patients, independently of preload responsiveness, and may be associated with worsening upstream venous congestion.

Inclusion criteria: * Critically ill hospitalized patients * Age ≥ 18 years * Patients undergoing fluid loading at the discretion of the attending physician, following prediction of fluid responsiveness using any recommended maneuver or dynamic parameter, in the setting of acute circulatory failure requiring vasopressor support and/or mean arterial pressure \< 65 mmHg (or a decrease of ≥ 30 mmHg from baseline in patients with chronic hypertension), and/or other signs of hemodynamic instability (tachycardia, mottling, oliguria, hyperlactatemia) * Affiliated with a national health insurance system Exclusion criteria : * Formal refusal from the patient or legally representative after information * Patients transferred from another intensive care unit * Pregnant or postpartum patients * Acute respiratory distress (defined as respiratory rate ≥ 35 breaths/min and/or signs of increased work of breathing) * Ongoing acute coronary syndrome * Acute or pulmonale (defined by right ventricular dilation associated with paradoxical septal motion related to an abrupt increase in right ventricular afterload) * Primary pulmonary arterial hypertension * Intra-abdominal hypertension (intravesical pressure \> 15 mmHg) * Poor echogenicity precluding adequate echocardiographic assessment of the right ventricle * Severe valvular heart disease or early postoperative period following valvular surgery