The current study aims to investigate the efficiency and comparison of vasopressin and epinephrine in individual’s, selected as randomized clinical trial, referring to pre-hospital emergencies in Tehran. However, for evaluation the neurological status of patients, their sera were subjected to be examined by S100B after CPR. In one hand, the inclusion criteria will be the cardiopulmonary arrest, lack of carotid pulse, age above 18 years, and non-traumatic. On the other hand, the exclusion criteria will be the history of steroids use, pregnancy, and death at the entrance to the hospital. For each group, 50 samples will be collected from patients with arrest out of the hospital. According to the America Heart Association 2010 guidelines, vasopressin or epinephrine will be administered randomly. Then, the S100B in sera will be evaluated after 24 hours.