Cardiac arrest remains a leading cause of death, currently affecting >250,000 Europeans outside the hospital each year. Manual cardiopulmonary resuscitation (CPR) provides between 15 to 30 % of normal blood flow to the heart and brain. For out-of-hospital cardiac arrest, the return of spontaneous circulation (ROSC) is possible only for 20-40% of patients with trained resuscitation teams. However, only 5-10% of patients will survive with good neurological status. A good quality CPR, a short time before initiation of the resuscitation and a short delay before the first defibrillation have been associated with improved neurological outcome. Unfortunately it is currently impossible to obtain reliable information on the quality of the perfusion and oxygenation of organs during CPR. The current monitoring during CPR is limited to heart rhythm analysis, pulse rate evaluation and end tidal CO2 (EtCO2). The last one is the only parameter which have been linked with probability of ROSC and its value gives no indication of the long-term prognosis nor the neurological status.

Cerebral spectroscopy (near-infrared spectroscopy - NIRS) allows to measure with a noninvasive method the local oxygen saturation of the prefrontal cortex (rSO2), reflecting the balance between need and supply of brain oxygenation. This technique has been recently used in cardiac arrest showing a possible association between rSO2 measured during CPR and the occurrence of ROSC or survival. The quantitative measurement of the pupillary light reaction has been described to predict neurological outcome in the hospital for patient successfully reanimated after out-of-hospital cardiac arrest (OHCA). Recently, a feasibility study has shown that its use was also possible during CPR in the pre-hospital setting.

The investigators aim to study a composite prognostic factor combining quantitative rSO2 and automated pupillometry measured during CPR. The investigators hypothesized that the rate of survival with good neurologic outcome at 30 days will be lower in patients with rSO2 <30% for more than 5 min and an absent pupillary reflex more than 5 min or decreasing during CPR .

Inclusion Criteria:

• All adults with nontraumatic, out-of-hospital cardiac arrest

Exclusion Criteria:

• Traumatic cardiac arrest
• Patients who had achieved ROSC before inclusion patients with a do-not-attempt resuscitation order
• Patients < 18 years old
• Subjects known to be pregnant or breastfeeding

Out of Hospital cardiac arrest patient