Complications of fluid overload in heat casualty prevention during field training

Several troops evacuated from field training sites as heat casualties were determined to be fluid overload casualties. Common features of this paradoxical syndrome were dilute primary electrolytes with physical exhaustion and muscle weakness after rapid free water intake. A pattern of skipping meals, working in a hot and humid environment, and consuming large volumes of water as "protection against becoming a heat casualty" predisposed these troops to the physical impairment that they intended to avoid. The mechanisms leading to both appropriate and inappropriate physiological responses to free water replacement are discussed as a basis for avoiding this specific heat casualty situation.