Fluid Responsiveness Evaluation by a Non-invasive Method in CHildren

Overview

In this study, the investigators aim to validate a non-invasive marker of fluid-responsiveness in children with acute circulatory failure based on standardized abdominal compression. This would allow physicians to identify which patient could benefit from a fluid expansion, thus avoiding a potentially useless or even dangerous fluid expansion, leading to fluid overload. To this end, the investigators will evaluate the diagnostic accuracy (sensitivity and specificity) of stroke volume variation induced by standardized abdominal compression for the diagnosis of fluid responsiveness (based on the gold-standard test: significant increase in cardiac index after fluid expansion).

Fluid expansion is the cornerstone of acute circulatory failure treatment in children Although this therapy drastically reduced mortality, several studies in recent years have highlighted the adverse effects of excessive fluid expansion (leading to fluid overload). Currently, the search for indicators to predict fluid responsiveness is a major issue in intensive care. These indicators are based on Franck-Starling's law: if small changes in preload lead to an increase in cardiac output, then fluid responsiveness can be expected. However, in children, the only validated indicator (respiratory variability of peak aortic velocity) can only be used in the absence of any spontaneous respiratory movement, a rare situation in practice. Recently, two pediatric studies investigated a simple clinical test: hepatic or abdominal compression. This clinical maneuver, by increasing venous return via mobilization of the hepato-splanchnic reserve, induces a transient and reversible preload increase. The evaluation of the hemodynamic effects of this "endogenous fluid expansion" allowed, according to the authors, to accurately predict fluid responsiveness. However, several factors reduce the applicability of these results: the small number of studies on this subject, the smaller volume of fluid used than in clinical practice, and the population studied, composed almost exclusively of children in postoperative of cardiac surgery. In this study, the investigators will evaluate the diagnostic accuracy of abdominal compression for the diagnosis of fluid responsiveness in children with acute circulatory failure, hospitalized in pediatric intensive care unit (PICU) for a medical or a non-cardiac surgical condition, for whom a fluid expansion was prescribed by the physician in charge. The index test will be the stroke volume variation following a standardized abdominal compression (before fluid expansion). The gold standard test will be the variation of cardiac output between baseline and after fluid expansion, a variation \> 15% defining fluid responsiveness. In this non interventional study of diagnostic accuracy, patients will undergo an extra echocardiographic assessment, but no supplemental blood test or invasive parameters will be collected. Simple clinical parameters will be collected within 4 hours after the fluid expansion. Patients will be follow-up until PICU discharge.