Treatment of Hypothermia in Trauma Victims: Thermodynamic Considerations

The relatively high specific heat of the human body makes hypothermia very difficult to treat. Although there are many treatment methods available, most evaluations of rewarming techniques are based on clinically observed rewarming rates, and they do not take into account initial core temperature, ambient temperature, the patient's own heat production, the effects of anesthesia, paralytic agents, and other variables. A heat transfer model is proposed that simulates the flow of heat through the body of a hypothermic patient. The model uses first principles involved in heat transfer and thermodynamics to describe the effects of currently available rewarming techniques. A commercially available routine is used to solve the equations, which also include any heat exchange between the patient's body and the environment, as well as metabolic heat generation as a function of time and core temperature. This thermodynamic analysis of rewarming, based on computer modeling of heat transfer, provides a scientific basis on which to establish guidelines for appropriate selection of treatment strategies for hypothermia, and it indicates that direct blood warming or infusion of warm intravenous fluids are the most effective rewarming techniques.