This study will involve the use of therapeutic hypothermia, an accepted medical treatment recommended for comatose post resuscitation patients by the International Liaison Committee on Resuscitation (ILCOR), the American Heart Association (AHA), and the European Resuscitation Council. This prospective cohort pilot study will evaluate the clinical performance of a new device, the ThermoSuit™ System, to achieve therapeutic hypothermia in comatose patients following resuscitation from cardiac arrest, and the impact of the vasodilator, magnesium sulfate, on cooling performance and hemodynamics in these patients. 14 patients will be prospectively randomized to receive either magnesium sulfate or normal saline (placebo) in this study.