Conducting a rigorous out-of-hospital study on patients in cardiac arrest is a daunting task. It requires training all members of the emergency medical system, randomization in the field (most commonly via a central physician-dispatcher), obtaining an exception to the typical requirement of informed consent, and rapidly administering a study drug in the field via an intravenous catheter that must be placed in a pulseless patient. All of this must occur in the chaotic and emotionally charged setting of a cardiac arrest, where every second counts with a dying patient, often in the presence of distraught family members and other bystanders. The intervention must not delay or interfere with the standard care the patient must receive, including high-quality cardiopulmonary resuscitation, defibrillation, obtaining and transmitting important information about the event and prior medical conditions, documenting all care administered and events that take place, communication with the receiving hospital, and preparation for transport. These are critically ill cardiac arrest patients in whom less than 2% survive to hospital discharge so the search for a more effective therapy is compelling.