Wilderness and Rescue Medicine 8th Edition

Chapter 18: Cold Injuries

Frostbite injures tissue through a complex pro- cess involving ischemia to infarction, metabolic derangement, cellular dehydration, ice crystal for- mation, blood clots, and inflammation. Trench foot is tissue damage from prolonged cold- induced vasoconstriction, resulting in ischemia and associated pain, inflammation, swelling, and secondary infection. Because nerves are the first to be affected by ischemia, the earliest symptom of cold injury is often numbness, explaining why it is easy to ignore at first. Not only can the tissue damage be a serious medical problem, but the loss of use of hands or feet can be a challenge to survival in a difficult situation. Frostbite Contact with subfreezing air, rock, or ice is required to produce frostbite. It is unlikely to occur above a temperature of -15°C unless heat loss is accelerated by the evaporation of a volatile liquid like gasoline. Tissue will not freeze if the ambient temperature is at or above 0°C, even with wind chill.

General Principles

Frostbite

Mechanism: • Ambient temperature below -1 5 ° C • Vasoconstriction and ischemia • Metabolic derangement and cellular dehydration Problem: • Swelling and inflammation • Ischemia to Infarction • Infection

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Superficial Frostbite The precursor to frostbite is sometimes called frostnip . This occurs with the intense vasocon- striction and loss of local tissue perfusion that results from exposure to subfreezing temperatures. The patient may not be aware of the problem, but sensation to touch is usually intact and occasion- ally painful. The area appears pink or white, but still feels soft to the touch. Ice crystals may form on the surface, but not within the tissue. In frostnip, only the outer layers of skin are affected. Damage is minimal and prompt rewarm- ing at this stage does not result in disability or tissue loss. Simply covering the area and warming the patient to reverse shell/core compensation is usually enough. The patient may experience mild