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Cold weather has been known to be a threat to humans since the beginning of recorded history. Cold injury as a threat has intensified during periods of armed conflict. Its devastating results were detailed during the American Revolution and in Napoleon’s campaign in Russia, and similar devastating experiences occurred in World War I, World War II, and the Korean conflict. Frostbite, immersion foot, and trench foot continue to challenge those subjected to cold weather, with or without wet conditions, emphasizing that prevention and successful treatment are not universal.
Preventing cold injury is of paramount importance. Yet, during times of armed conflict, prevention may be increasingly difficult. Cold injury during certain sporting activities such as mountain climbing and skiing also continues to be a significant challenge, particularly for the least-experienced participants. Cold injury usually occurs during combat situations when combatants are exposed to cold weather for prolonged periods without adequate clothing; similar injuries can occur among elderly civilians and those who are intoxicated.
Hypothermia
Hypothermia is a diagnosis made by identifying a temperature by thermometer or thermistor probe below 35°C or 95°F. Elderly persons, who have more difficulty in perceiving temperature changes, are particularly susceptible to hypothermia. Elderly persons with less total body water than those who are younger also have a reduced shivering response and a reduced ability to store heat. The most common symptom of hypothermia is an altered state of consciousness, and this may be evidenced by agitation, confusion, mood changes, poor judgment, and even coma. The patient can appear cyanotic or gray, and the skin is cool to touch. With severe hypothermia, shivering may be absent. Often, blood pressure and pulse rate are decreased.
Increased urinary output with hypothermia can result in volume depletion and dehydration. Normal reabsorption of water and glucose are prevented, and there is a decreased secretion of antidiuretic hormone. Diminished insulin production associated with decreased peripheral glucose utilization can result in hyperglycemia. Acidosis is usually present, and it can be a combination of metabolic and respiratory acidosis. Hemoconcentration and increased blood viscosity occur. There is a partial impairment of the delivery of oxygen to tissues.
If the core body temperature falls below 33°C, severe hypothermia exists. With falling temperature, sinus bradycardia can develop that does not respond to therapy, including atropine therapy. On the electrocardiogram, a slowing of conduction may be seen, as well as T-wave inversion and a characteristic J wave, which is a positive deflection in the left ventricular leads at the junction on the QRS and ST segments.
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