Penetrating mechanisms of injury are by far the most common, with explosive devices and gunshot wounds responsible for nearly all vascular injuries during wartime [6, 7, 12, 25]. In OIF, improvised explosive devices were the cause of vascular injury in 55 % of patients, and gunshot wounds accounted for 39 % of injuries [25, 36, 37]. In one study of these penetrating injuries, 110/111 US casualties survived the immediate repair of an extremity arterial injury. This subgroup had a mean graft patency rate of 84.9 % at 347 days (range 29–1,079 days) and a primary amputation rate of 14.2 % (16/113) after surgical treatment in the US military hospitals of Iraq and Afghanistan. This outcome is especially important given their initial physiologic derangements and may have strong implications for utilizing fresh blood products in equal ratios when arterial reconstruction is attempted over a primary amputation (Table 27.2) [13].