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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 extra cellular 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 micro vascular 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 clinical features.

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.

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° CD 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.
• In severe hypothermia. core temperature drops to 77° to 86° F (25° to 30° C), with loss of deep tendon reflexes and ventricular fibrillation. The patient may appear dead, with no palpable pulse or audible heart sounds. His pupils may dilate, and he'll appear to be in a state of rigor mortis. A temperature drop below 77° F (25° C) causes cardiopulmonary arrest and death.

Diagnosis

Treatment

In a localized cold injury, treatment consists of rewarming the injured part, supportive measures and, sometimes (in severe cases), a fasciotomy to increase circulation by lowering edematous tissue pressure. However, if gangrene occurs, amputation may be necessary.

In hypothermia, therapy consists of immediate resuscitative measures, careful monitoring, and gradual rewarming of the body.

Exercise

Exercise is an important method of heat production. Muscles, which make up 50 percent of our body weight, produce 73 percent of our heat during work. Short bursts of hard physical effort can generate tremendous amounts of heat, while moderate levels of exercise can be sustained for long periods. This valuable source of heat does have its limitations. Physical conditioning, strength, stamina and fuel in the form of food and water are necessary to sustain activity.

An important heat source for infants and hibernating mammals is the oxidation of brown fat from deposits on their abdomen, in their armpits and behind their shoulders. Oxidizing or burning brown fat produces considerable heat--of particular significance for infants, who because their small size have a large surface area for heat loss. Brown fat cells are almost completely absent in adult humans.

Preventing Cold Injuries

Individuals vary in their response to cold exposure, with some more affected than others. But it is important for everyone to reduce heat loss following exercise in cold environments in order to avoid possible cold injury. The key protective measures are to get out of the cold environment as quickly as possible, remove wet clothing and add extra layers, taking care to cover high risk areas such as hands, feet and head. Some of the important steps to prevent cold injuries are:-

• wear layers of warm clothing, with an outer jacket that is wind-resistant. Mittens, boots and a hat are also important. (We lose a large portion of our body heat from the head.)
• when the wind chill is high, try to cover as much exposed skin as possible.
• the use of alcohol, tobacco and certain medications will increase your susceptibility to cold
• walking or running will help keep you warm by generating body heat