Hypothermia is very common in the combat casualty and is an independent predictor of mortality in this setting similar to reports from civilian trauma centers. Hypothermia management in the combat zone is largely focused on use of a variety of active and passive external warming methods which have been recommended by the Joint Theater Trauma System. Comprehensive experimental comparison of various combinations of military fielded external warming devices is lacking.
Using a simple, closed, circulating fluid model, dozens of warming setups are compared. These setups are comprised of military fielded hypothermia prevention and treatment materials to include forced air blankets, chemical blankets, human remains pouches, space blankets, and wool blankets. Testing was standardized and temperature changes were recorded for 40 minutes. Six of the setups underwent four rounds of repeat testing to assess reproducibility.
Forced air blankets performed best for active external warming. The warming effect was greatest when placed in direct contact with the model and insulated from above. Space blankets were the best insulator, but combinations of other materials achieved similar results. Human remains pouches also improved warming, especially when insulated from within with space blankets but were noted to be difficult to set up. Forced air blanket setups with the 6 or more layers performed significantly better than those with the fewer than 6 layers (p < 0.003). Repeated trials showed excellent reproducibility.
Forced air blankets appear to be the most effective military fielded hypothermia treatment material. Layering of military fielded hypothermia management materials hastens warming and should be incorporated into warming strategies when practical.
Although performance differences between our warming setups were large, clinical significance regarding warming an actual hypothermic patient remains to be determined. Further testing, using a more sophisticated model is warranted. Until this data is obtained we feel that the information presented here should be considered when choosing a method to actively warm a combat trauma patient.
Jeffrey Mikita, No Financial Disclosure Information; No Product/Research Disclosure Information