 The current research protocol was formulated in an attempt to develop new treatment options for patients who develop an in-hospital VF or pVT arrest refractory to electrical defibrillation with the specific goal of improving patient outcomes. The trial will utilize pre-filled, blinded syringes of Metoprolol in patients who develop an in-hospital cardiac arrest due to ventricular fibrillation or pulseless ventricular tachycardia see study protocol. 