Cold injuries
Overexposure to cold air or water causes cold injuries. They occur in two major forms: localized injuries (such as frostbite) and systemic injuries (such as hypothermia). Untreated or improperly treated frostbite can lead to gangrene and may necessitate amputation; severe hypothermia can be fatal.
The risk of serious cold injuries, especially hypothermia, is increased by youth, lack of insulating body fat, wet or inadequate clothing, old age, drug abuse, cardiac disease, smoking, fatigue, hunger and depletion of caloric reserves, and excessive alcohol intake (which draws blood into the capillaries and away from body organs).
Causes
The specific causes of frostbite and hypothermia vary.
Frostbite
Localized cold injuries occur when ice crystals form in the tissues and expand extracellular spaces. With compression of the tissue cell, the cell membrane ruptures, interrupting enzymatic and metabolic activities. Increased capillary permeability accompanies the release of histamine, resulting in aggregation of red blood cells and microvascular occlusion. Frostbite results from prolonged exposure to dry temperatures far below freezing.
Hypothermia
Chemical changes result from hypothermia that slow the functions of most major organ systems, such as decreased renal blood flow and decreased glomerular filtration. Hypothermia results from cold-water near-drowning and prolonged exposure to cold temperatures.
Signs and symptoms
Both frostbite and hypothermia produce distinctive signs and symptoms.
Frostbite
Two types of frostbite can occur: superficial or deep. Superficial frostbite affects skin and subcutaneous tissue, especially of the face, ears, extremities,
and other exposed body areas. Although it may go unnoticed at first, upon returning to a warm place, frostbite produces burning, tingling, numbness, swelling, and a mottled, blue-gray skin color.
and other exposed body areas. Although it may go unnoticed at first, upon returning to a warm place, frostbite produces burning, tingling, numbness, swelling, and a mottled, blue-gray skin color.
Deep frostbite extends beyond subcutaneous tissue and usually affects the hands or feet. The skin becomes white until it’s thawed; then it turns purplish blue. Deep frostbite also produces pain, skin blisters, tissue necrosis, and gangrene.
Hypothermia
Indications of hypothermia (a core body temperature below 95° F [35 C]) vary with severity.
Mild hypothermia produces a temperature of 89.6° to 95° F (32° to 35° C), severe shivering, slurred speech, and amnesia.
Moderate hypothermia results in a temperature of 86° to 89.6° F (30° to 32° C), unresponsiveness or confusion, muscle rigidity, peripheral cyanosis and, with improper rewarming, signs of shock.
