Cold injuries are caused by overexposure; they occur in two major forms: localized injuries (frostbite) and systemic injuries (hypothermia).
Frostbite may be superficial or deep. Superficial frostbite affects skin and subcutaneous tissue, especially of the face, ears, extremities, and other exposed body areas. Deep frostbite extends beyond the subcutaneous tissue and usually affects the hands and feet. Untreated or improperly treated frostbite can lead to gangrene, requiring amputation.
Hypothermia - core body temperature below 95° F (35° C) - effects chemical changes in the body. Severe hypothermia can be fatal.
Frostbite results from prolonged exposure to freezing temperatures or to cold, wet environments. The cold causes ice crystals to form within and around tissue cells. This in turn causes cell membranes to rupture, interrupting enzymatic and metabolic activities. Increased capillary permeability accompanies the release of histamine, resulting in aggregation of red blood cells and microvascular occlusion.
Hypothermia results from cold-water near drowning and prolonged exposure to cold temperatures. It also can occur in normal temperatures if disease or debility alters the patient's homeostasis. The administration of large amounts of cold blood or blood products can cause hypothermia. In hypothermia, metabolic changes slow the functions of most major organ systems, resulting in decreased renal blood flow and decreased glomerular filtration.
Technetium pertechnetate scanning shows perfusion defects and deep tissue damage and can be used to identify nonviable bone. Doppler and plethysmographic studies help determine pulses and the extent of frostbite after thawing.
Essential laboratory tests during treatment of moderate or severe hypothermia include a complete blood count, coagulation profile, urinalysis, and serum amylase, electrolyte, hemoglobin, glucose, liver enzyme, blood urea nitrogen, creatinine, and arterial blood gas levels.
For frostbite injuries, treatment consists of rapidly rewarming the injured part to slightly above ideal body temperature to preserve viable tissue. Slow rewarming could increase tissue damage. Treatment also includes administration of antibiotics and tetanus prophylaxis, as needed, and narcotic analgesics to relieve pain when the affected part begins to rewarm.
After rewarming, the affected part is kept elevated, uncovered, at room temperature. A regimen of whirlpool treatments for 3 or more weeks cleans the skin and debrides sloughing tissue. After the early stage, active range-of-motion exercises restore mobility. Surgery usually isn't required, but amputation may be necessary if gangrene develops.
Treatment for hypothermia consists of supportive measures and specific rewarming techniques, including:
Any arrhythmias that develop usually convert to normal sinus rhythm with rewarming. If the patient has no pulse or respirations, cardiopulmonary resuscitation (CPR) is needed until rewarming raises the core temperature to at least 89.6° F (32° C).
Administration of oxygen, endotracheal intubation, controlled ventilation, I.V. fluids, and treatment of metabolic acidosis depend on test results and careful patient monitoring.
To prevent hypothermia and frostbite in cold conditions, wear layered clothing to create insulation. This should include mittens or gloves, a cap or hood, thermal underwear, and multiple layers of socks. Be sure to change wet garments promptly and drink plenty of fluids to avoid dehydration.
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