Several previous South Korean studies have compared treatments using epinephrine only with those using epinephrine, vasopressin, and steroid during cardiopulmonary resuscitation (CPR) of cardiac arrest (CA)patients in the hospital. The vasopressin-steroid-epinephrine (VSE) group was reported to show a better return of spontaneous circulation (ROSC), lower whole-body inflammatory reaction, less cases of organ failure, and more cases of survival and hospital leave while showing better results of neurological prognosis. However, studies are lacking on treatment of cardiac arrest (CA) cases outside the hospital. In addition, because the three drugs of the vasopressin-steroid-epinephrine (VSE) regimen are used together, it is hard to identify which of them is most effective. Investigators are implementing a multicenter, prospective study to compare the use of vasopressin, steroid, and both vasopressin and steroid in post-cardiac arrest (CA) patients outside the hospital and examine the effects on ROSC and neurological score in this population.