The patient is in shock that does not respond to fluids. In the ABCDE order, circulation is dealt with before disability (the head injury), so the source of bleeding must be found first. FAST is the quick bedside test for intra-abdominal bleeding and hemopericardium in hypovolemic shock. Craniotomy or burr holes come after hemodynamic control. A full-body CT is not appropriate in an unstable patient, and laparotomy before any evidence of abdominal bleeding is premature.