Patients over 19 years of age admitted to our hospital after succesful resuscitation from out of hospital cardiac arrest. Mental state of the patient is less than 8 in GCS scale and the patient should be undergoing therapeutic hypothermia.Exclusion criteria is age younger than 19 years, terminal illness or do-not resuscitation status, pre-existing coma, abnormal mental status with defined intracranial lesion (ex. cerebral hemorrhage, cerebral infarction, etc), unstable vital sign and previous end-stage renal disease.