The principal purpose of this study is to describe the changes in cerebral circulation (assessed by transcranial ultrasound) and oxygenation (assessed by Near InfraRed spectroscopy, NIRS) during resuscitation for hemodynamic failure (arterial hypotension or shock) in critically ill children treated with vasoactive or inotropic drugs.

The secondary objectives are :

i) to evaluate the association between an alteration of cerebral circulation and/or oxygenation and an alteration in macro-circulatory parameters (Mean Arterial Blood Pressure and cardiac output) or a bad outcome, ii) to study if cerebral autoregulation is impaired

Pediatric shock is a frequent and serious cause of hospitalization in pediatric intensive care unit that can lead to multi-organ failure and death.

Its early recognition improves patients' outcome, as well as the establishment of targeted guidelines pursuing normalization of macro-circulatory parameters (ie blood pressure and lactate).

However, regional hypoperfusion leading to organ failure can be present before the alteration of these parameters, and persist after their restoration.

Brain lesions are common in critically ill children with cerebral hypoperfusion, since they may have impaired autoregulation and permeable blood-brain barrier. Vasoactive and inotropic drugs used for hemodynamic resuscitation should restore systemic and regional circulation, but may be inadequate on brain perfusion because of i) their variable and unpredictable cardiovascular effects , and ii) a strong interindividual variability between patients. As such, the impact of this medication on cerebral circulation and oxygenation is unknown.

Monitoring cerebral circulation and oxygenation during a hemodynamic resuscitation using catecholamines is a first step to identify risk factors of an altered brain perfusion, and to improve treatment of shock.

Inclusion Criteria:

Neonates and children from 0 to 18 years old hospitalized in pediatric intensive care unit (PICU) with hemodynamic failure requiring vasoactive or inotropic treatment. This includes :

• shock (tachycardia, troubles of peripheral perfusion with capillary refill time >3 sec, oliguria, with or without alteration of consciousness or arterial hypotension)
• isolated arterial hypotension if it needs medical treatment to readjust balance between oxygen demand and oxygen consumption

Exclusion Criteria:

• primitive cerebral lesion: traumatic or neurosurgical (including brain death states)
• preterm neonates of less than 37 weeks gestational age
• patients already receiving more than one catecholamine
• patients too instable, defined by a respiratory instability (pulse oxymetry of less than 80% during more than 5 minutes) and/or hemodynamic instability (variability of blood pressure and heart rate of more than 50%) and/or cardiorespiratory arrest.

Pediatric patients hospitalized in 4 french Pediatric Intensive Care Units