Determination of vital and functional outcome in comatose survivors after cardiac arrest is principally based on the identification of predictors of non-awakening, using by clinical, biological and electrophysiological tools. In patients without presence of non-awakening predictors, it would be of interest to identify predictive criteria of awakening. The presence of mismatch negativity during the cortical auditory-evoked potential could contribute to further progress in neurological prognostication of these patients. However, at this time, its prognostic value has been insufficiently studied and the optimal time of realization remains unknown.

We hypothesized that the presence of the mismatch negativity during the cortical auditory-evoked potential would predict a favorable outcome in comatose survivors after cardiac arrest.The main objective is to determine the capacity of the presence of the mismatch negativity during the cortical auditory-evoked potential to predict a 1-year favorable outcome in comatose survivors after cardiac arrest

The secondary objectives are:

• To assess the capacity of the presence of the mismatch negativity during the cortical auditory-evoked potential to predict awakening during the hospitalisation stay.
• To determine the optimal time of realization of the cortical auditory-evoked potential
• To determine the capacity of the presence of the mismatch negativity during the cortical auditory-evoked potential to predict ICU discharge and/or hospital discharge favorable outcome in comatose survivors after cardiac arrest
• To determine the impact of the sedations drugs during the hypothermia phase, and during the ICU stay The main judgement criterion is the 1-year CPC score (CPC 1 to 2 as a favorable outcome)

Study design : Prospective, multicentre, interventional study. Decision making to withdrawal of life support will be strictly codified according current knowledge and standardized among the participating centres. In the absence of predictors of non-awakening, care will be continued without limitation. The design of the study will focus on the determination of the capacity of the presence of the mismatch negativity during the cortical auditory-evoked potential to predict awakening. Cortical auditory-evoked potential will be performed bedside in the ICU by qualified neurophysiologists. Results of cortical auditory-evoked potential will remain blinded of bedside clinicians providing care for the patients. Awakening will be assessed bedside daily. CPC score will be evaluated at discharge of the ICU, of the hospital, at 3 months and 1 year by an independent evaluator, blinded of the results of the cortical auditory-evoked potentials.

Inclusion Criteria:

• Adults (age ≥ 18 years)
• hospitalized in the intensive care unit in the aftermath of a intra-or extra-hospital cardiac arrest
• alive but remaining comatose between the 2nd day and the 5th day after cardiopulmonary arrest

Exclusion Criteria:

• moribund patients (treatment limitations or the life expectancy of the inclusion estimated at less than 1 year)
• patient awake at day of potential inclusion
• brain death state
• failure to realize the cortical
• patient whose hearing loss is known