Patient Care Protocols Prehospital protocols for adult cardiac arrest patients within Mecklenburg County state that all first responders follow advanced cardiac life support (ACLS) algorithms during cardiopulmonary resuscitation. Current MEDIC protocols specify that initial vascular access be obtained by paramedics via either tibial or humeral IO needle insertion, followed by peripheral IV for secondary access. This study will randomize initial vascular access to a humeral IO, tibial IO, or peripheral IV.