Inclusion Criteria:  Newborn and infant <2 years. Born at or near term (> 36 weeks of amenorrhea). Hospitalized in pediatric and neonatal intensive care. Requiring the use of invasive mechanical ventilation. In a state of shock defined by a cardio-circulatory dysfunction associating arterial hypotension, an alteration in organ perfusion, one or more organ dysfunctions or vasopressor's requirement. Clinical signs retained: heart rate ≥ 90th percentile associated with at least one sign of peripheral hypoperfusion represented by a a capillary refill time ≥ 3sec, or the presence of mottling or coldness of the extremities or urine output ≤ 0.5ml / kg / h or disturbance of consciousness. The practitioner in charge of the patient has decided to perform volume expansion. Non-opposition expressed by the holders of parental authority.  Exclusion Criteria:  Any serious and urgent clinical hemodynamic situation, the management of which would be delayed by inclusion in the protocol. Patient with unoperated congenital heart disease. Patient in spontaneous or non-invasive ventilation or with spontaneous ventilatory cycles in invasive ventilation. Patient in prolonged cardiac arrest (> 5min) or refractory. Patient under venous-arterial extracorporeal membrane oxygenation. Refusal of the holders of parental authority to exploit the collected data.