Low Dose Vasopressin in Traumatic Shock

Inclusion Criteria: To be eligible for enrollment in the study, a patient must meet all of the follow criteria at assessment: * Patient is a male or female patient presumed to be at least 18 years of age; * Patient has a systolic blood pressure \< 90 mmHg; * Patient has clinical evidence of acute traumatic injury; * Infusion of study drug must start within one hour following SBP (systolic blood pressure) \< 90 mmHg Exclusion Criteria: A patient meeting any one of the following criteria at hospital assessment is not eligible for enrollment: * Patient is admitted to one of the study hospitals' Emergency Department greater than six hours after injury; * Patient has received greater than 4 liters fluid since time of injury; * Patient is enrolled in another shock trial; * Patient is asystolic or requires CPR (cardiopulmonary resucitation) prior to randomization; * Female patient is pregnant by report or suspicion; * Patient has known "Do Not Resuscitate" orders or visible/identifiable method of objection to participation (e.g., exclusion bracelet);