Cardiac arrest is a major public health problem, with 700 000 cases per year , and a survival ranging from 4 to 33%. The post- anoxic encephalopathy remains the most serious complication with only a third of survivors . It is due to a series of phenomena involving microcirculation disorders . Cerebral oximetry is a new technique to evaluate the microcirculatory status . To this day it is used in cardiovascular surgery at risk of cerebral hypoperfusion where desaturation of cerebral oximetry is synonymous with ischemia and microcirculatory disorders. Therapeutic hypothermia is the only treatment improves the outcome of patients after extra- hospital cardiac arrest resuscitation . Its mechanisms of action seem to change all the phenomena responsible for microcirculatory reperfusion disorders . Currently it is recommended to practice hypothermia between 32 and 34 ° C. However, a recent study suggests a superiority of hypothermia at 32 ° C rather than 34 ° C.

The hypothesis of this study is that cerebral oximetry value will be different in patients subjected to two different levels of therapeutic hypothermia in the aftermath of an extra- hospital cardiac arrest. These data allow a better understanding of the mechanisms underlying the benefit of this technique.

Inclusion Criteria:

• Patient presented with an extra-hospital cardiac arrest resuscitation and to benefit from therapeutic hypothermia using a servo system to its temperature (CoolGard 3000 ® system)
• Age> 18 years and <80 years

Exclusion Criteria:

• Major Patient protected by law
• Private person administrative or judicial freedom
• Neurological or traumatic cause of cardiac arrest
• Pregnancy