The prevention of hypothermia in military casualties under field conditions is challenging. The efficacy of a baffled reflective Blanket (Blizzard Blanket), a portable intravenous fluid warmer (Thermal Angel), and wool Blankets (control) in preventing hypothermia was tested under military field conditions in a swine hemorrhagic shock model. Fifteen pigs were bled at 10 degrees C. After 45 minutes, Hextend was administered (groups 1 and 3, at 10 degrees C; group 2, via Thermal Angel); groups 2 and 3 were encircled with a Blizzard Blanket. After 120 minutes, the pigs were moved to 21 degrees C to simulate a field hospital; group 1 was covered with Blankets. Blood was administered (groups 1 and 3, at 4 degrees C; group 2, via Thermal Angel) with 180 minutes of monitoring. The core temperature was <35 degrees C in five of five control pigs, four of five Blizzard-only pigs, and one of five Thermal Angel plus Blizzard Blanket pigs. The Blizzard Blanket limited but did not prevent hypothermia. The Thermal Angel plus Blizzard Blanket combination prevented hypothermia. The Thermal Angel is useful for bolus administration when electricity is limited; its military field use is constrained by battery weight and battery life.