Neurological Prognostication of Patients in Therapeutic Hypothermia After Cardiac Arrest

3500 people suffer from out of hospital cardiac arrest each year in Denmark. Therapeutic hypothermia to 33 degrees celsius is now standard treatment of comatose cardiac arrest patients. The investigators are challenged in our attempt to predict outcome of these patients by both low body temperature in itself and the sedative and relaxing drugs used to keep the patient in a coma. This study is a substudy in a large international multicenter randomized trial that investigates the possible benefit of 48 hours of therapeutic hypothermia versus todays standard of 24 hours. In this substudy the investigators will approach early prediction of neurological outcome using a combination of new examinations backed up by well established ones to engage this challenge from different angles and find a battery of combined examinations, that together will enable us to accurately predict outcome at an earlier stage. Our examinations have been chosen from the three fields of neurophysiology, biochemistry and neurology and consist of electroencephalography (EEG), somatosensory evoked potentials (SEP), biomarkers and clinical examinations such as brain stem reflexes chosen for their prognostic reliability.