With the cold months here people need to be made aware of injuries that may occur during these months. Exposure to a temperature below freezing usually leads to severe soft tissue damage (Figure 1).

How does the body protect itself from cold?

 The body has the ability to maintain a core body temperature by the process of thermoregulation. During extreme cold, the body receives a signal from sensory receptors. For example, there receptors are present in the hands or the feet (Figure 2). These sensory receptors will respond to the cold and send a signal up to the brain. The posterior hypothalamus is responsible for regulating body temperature during exposure to cold. The anterior hypothalamus responds to heat. Once the signal reaches the brain, the brain then sends a signal to the body in order to respond to cold temperatures and to maintain a core body temperature. This is necessary in order to provide the vital organs with the necessary heat to function properly. The brain will send a signal to the smooth muscle cells of the blood vessels of the skin and the skeletal muscles.

The smooth muscle cells lines the arteries and arterioles. During cold temperatures, the signal from the brain causes vasoconstriction of the arterioles in the skin which allows the body to shift the blood to more vital areas of the body (Figure 3). When the temperature is at or below 0°C (degrees Celsius), which is about 32°F, the blood vessels close to the skin start to constrict which helps to preserve the core body temperature.

Another signal from the brain gores to the skeletal muscles which quickly contracts them causing shivering that helps to keep the body warm. As the body forces the muscle to work (shivering), it breaks down ATP that will also release energy (Figure 4). ATP is converted into ADP and releases free phosphate (P) and energy to warm up the body.

The condition of frostbite usually affects the hands and the feet (Figure 5). When the temperature drops below -2°C, ice crystals are formed in the extracellular fluid (Figure 6). The water moves from the intracellular compartment to the extracellular compartment causing cell dehydration and death. The sensory nerve endings are affected early and the condition can be painless.

Causes of frostbite include inadequate circulation in below freezing weather, inadequate clothing, wind chills, wet clothes, poor circulation, tight boots, cramped position, smoking, alcohol use, diabetes, peripheral neuropathy and certain medications such as beta blockers.

Clinical Features
 The patient may have skin erythema, edema and there may be the presence of mottled skin (Figure 7). In most significant cases, blisters will be present. The blisters may be painless. There are usually two kinds of blisters; superficial lesions and deeper lesions. The superficial lesions are due to a partial thickness injury. These are white clear blisters. Hemorrhagic blisters from a deeper lesion indicate a full thickness injury.

 The involved extremity will be either splinted or wrapped. Warm the person and wrap a blanket around them, rapidly warming at a temperature of 40–42°C for about 15–30 minutes. Do not rub or massage the involved extremity. When blisters are present and are clear or white (superficial lesion) a debridement should be performed. If the blisters are hemorrhagic, drain the blisters but leave the overlaying skin intact. Hemorrhagic blister are a sign of a deeper lesion and they are usually covering a deep significant injury.

Amputation for the necrotic tissue is always delayed. There is a need to wait for demarcation of the zone of injury except in severe infections or gas gangrene. There is an old saying that states “if the extremity is frozen in January, it should be amputated in July”.

If the condition of frostbite occurs in children, it may lead to a cartilage or growth plate injury and the child may later on develop short digits.

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Originally published at www.huffingtonpost.com on December 27, 2016.