Metabolic Fluid Responsiveness in Children

Inclusion Criteria: * Age less than or equal to 15 years old * Hospitalization in a pediatric intensive care unit after cardiac surgery * Prescription by the attending physician of a fluid expansion of 10ml/kg * Prescription of arterial and venous blood gas before and after the volume expansion to help manage acute circulatory failure * Patient implanted with a functioning arterial line * Patient implanted with a functioning central venous line in the superior vena cava territory Exclusion Criteria: * Patient less than 37 weeks' corrected gestational age * Hemodynamic instability making the delay necessary for any test dangerous * Supine position contraindicated or deleterious * Impairment of echocardiographic acoustic window or restless patient making ultrasonography impossible * Opposition to participate expressed by the patient or by a parent or legal guardian