Frostbite

Frostbite

Overview
Frostbite is the medical condition where localized damage is caused to skin
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...

 and other tissues
Tissue (biology)
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...

 due to extreme cold. Frostbite is most likely to happen in body parts farthest from the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

 and those with large exposed areas. The initial stages of frostbite are sometimes called "frost nip".

There are several classifications for tissue damage caused by extreme cold including:
  • Frostnip is a superficial cooling of tissues without cellular destruction.
  • Chilblains are superficial ulcers of the skin that occur when a predisposed individual is repeatedly exposed to cold
  • Frostbite involves tissue destruction.


At or below 0 °C (32 °F), blood vessels close to the skin start to constrict, and blood is shunted away from the extremities via the action of glomus bodies
Glomus body
A glomus body is a component of the dermis layer of the skin, involved in body temperature regulation. The glomus body consists of an arterio-venous shunt surrounded by a capsule of connective tissue. Glomus bodies are most numerous in the fingers and toes...

.
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Encyclopedia
Frostbite is the medical condition where localized damage is caused to skin
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...

 and other tissues
Tissue (biology)
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...

 due to extreme cold. Frostbite is most likely to happen in body parts farthest from the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

 and those with large exposed areas. The initial stages of frostbite are sometimes called "frost nip".

Classification


There are several classifications for tissue damage caused by extreme cold including:
  • Frostnip is a superficial cooling of tissues without cellular destruction.
  • Chilblains are superficial ulcers of the skin that occur when a predisposed individual is repeatedly exposed to cold
  • Frostbite involves tissue destruction.

Stages


At or below 0 °C (32 °F), blood vessels close to the skin start to constrict, and blood is shunted away from the extremities via the action of glomus bodies
Glomus body
A glomus body is a component of the dermis layer of the skin, involved in body temperature regulation. The glomus body consists of an arterio-venous shunt surrounded by a capsule of connective tissue. Glomus bodies are most numerous in the fingers and toes...

. The same response may also be a result of exposure to high winds. This constriction helps to preserve core body temperature. In extreme cold, or when the body is exposed to cold for long periods, this protective strategy can reduce blood flow in some areas of the body to dangerously low levels. This lack of blood leads to the eventual freezing and death of skin tissue in the affected areas. There are four degrees of frostbite. Each of these degrees has varying degrees of pain.
  • First degree

This is called frostnip and this only affects the surface skin, which is frozen. On the onset, there is itching and pain
Pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...

, and then the skin develops white, red, and yellow patches and becomes numb.
The area affected by frostnip usually does not become permanently damaged as only the skin's top layers are affected. Long-term sensitivity to both heat and cold can sometimes happen after suffering from frostnip.
  • Second degree

If freezing continues, the skin may freeze and harden, but the deep tissues are not affected and remain soft and normal.
Second-degree injury usually blisters 1–2 days after becoming frozen. The blisters may become hard and blackened, but usually appear worse than they are. Most of the injuries heal in one month, but the area may become permanently insensitive to both heat and cold.
  • Third and Fourth degrees

If the area freezes further, deep frostbite occurs. The muscles, tendons, blood vessels, and nerves all freeze. The skin is hard, feels waxy, and use of the area is lost temporarily, and in severe cases, permanently. The deep frostbite results in areas of purplish blisters which turn black and which are generally blood-filled. Nerve damage in the area can result in a loss of feeling. This extreme frostbite may result in fingers and toes being amputated if the area becomes infected with gangrene
Gangrene
Gangrene is a serious and potentially life-threatening condition that arises when a considerable mass of body tissue dies . This may occur after an injury or infection, or in people suffering from any chronic health problem affecting blood circulation. The primary cause of gangrene is reduced blood...

. If the frostbite has gone on untreated, they may fall off. The extent of the damage done to the area by the freezing process of the frostbite may take several months to assess, and this often delays surgery to remove the dead tissue.

Risk factors


Risk factors
Risk factors
A risk factor is a concept in finance theory such as the CAPM, APT and other theories that use pricing kernels. In these models, the rate of return of an asset is a random variable whose realization in any time period is a linear combination of other random variables plus a disturbance term or...

 for frostbite include using beta-blockers and having conditions such as diabetes and peripheral neuropathy
Peripheral neuropathy
Peripheral neuropathy is the term for damage to nerves of the peripheral nervous system, which may be caused either by diseases of or trauma to the nerve or the side-effects of systemic illness....

.

Causes


Factors that contribute to frostbite include extreme cold, inadequate clothing, wet clothes, wind chill
Wind chill
Wind chill is the felt air temperature on exposed skin due to wind. The wind chill temperature is always lower than the air temperature, and the windchill is undefined at the higher temps...

, and poor blood circulation
Circulatory system
The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...

. Poor circulation can be caused by tight clothing or boots, cramped positions, fatigue, certain medications, smoking, alcohol use, or diseases that affect the blood vessels, such as diabetes.

Exposure to liquid nitrogen
Liquid nitrogen
Liquid nitrogen is nitrogen in a liquid state at a very low temperature. It is produced industrially by fractional distillation of liquid air. Liquid nitrogen is a colourless clear liquid with density of 0.807 g/mL at its boiling point and a dielectric constant of 1.4...

 and other cryogenic liquids can cause frostbite as well as prolonged contact with the chemical butane (see deodorant burn
Deodorant Burn
A deodorant burn is a burn inflicted by an aerosol. These types of Burns are often compared to frost bite in characteristics. The prolonged contact to skin with a deodorant can cause the contact area to freeze therefore creating a burn onto the effected area. Cases of deodorant burns are rare and...

).

Treatment


Do not make affected area (skin) touch any cold or hot objects. Keep affected area warm. Treatment of frostbite centers on rewarming (and possibly thawing) of the affected tissue. The decision to thaw is based on proximity to a stable, warm environment. If rewarmed tissue ends up refreezing, more damage to tissue will be done. Excessive movement of frostbitten tissue can cause ice crystals that have formed in the tissue to do further damage. Splinting and/or wrapping frostbitten extremities are therefore recommended to prevent such movement. For this reason, rubbing, massaging, shaking, or otherwise applying physical force to frostbitten tissues in an attempt to rewarm them can be harmful. Caution should be taken not to rapidly warm up the affected area until further refreezing is prevented. Warming can be achieved in one of two ways:

Passive rewarming involves using body heat or ambient room temperature to aid the person's body in rewarming itself. This includes wrapping in blankets or moving to a warmer environment.

Active rewarming is the direct addition of heat to a person, usually in addition to the treatments included in passive rewarming. Active rewarming requires more equipment and therefore may be difficult to perform in the prehospital environment. When performed, active rewarming seeks to warm the injured tissue as quickly as possible without burning them. This is desirable as the faster tissue is thawed, the less tissue damage occurs. Active rewarming is usually achieved by immersing the injured tissue in a water-bath that is held between 40-42°C (104-108F). Warming of peripheral tissues can increase blood flow from these areas back to the bodies' core. This may produce a decrease in the bodies' core temperature and increase the risk of cardiac dysrhythmias.

Surgery


Debridement and/or amputation of necrotic tissue is usually delayed. This has led to the adage "Frozen in January, amputate in July" with exceptions only being made for signs of infections or gas gangrene
Gangrene
Gangrene is a serious and potentially life-threatening condition that arises when a considerable mass of body tissue dies . This may occur after an injury or infection, or in people suffering from any chronic health problem affecting blood circulation. The primary cause of gangrene is reduced blood...

.

Prognosis


A number of long term sequelae can occur after frost bite. These include: transient or permanent changes in sensation, electric shocks, increased sweating, cancers, and bone destruction/arthritis
Arthritis
Arthritis is a form of joint disorder that involves inflammation of one or more joints....

 in the area affected.

Research


Evidence is insufficient to determine whether or not hyperbaric oxygen therapy
Hyperbaric oxygen therapy
Hyperbaric medicine, also known as hyperbaric oxygen therapy , is the medical use of oxygen at a level higher than atmospheric pressure. The equipment required consists of a pressure chamber, which may be of rigid or flexible construction, and a means of delivering 100% oxygen...

 as an adjunctive treatment can assist in tissue salvage. There have been case reports but few actual research studies to show the effectiveness.

Medical sympathectomy using intravenous reserpine
Reserpine
Reserpine is an indole alkaloid antipsychotic and antihypertensive drug that has been used for the control of high blood pressure and for the relief of psychotic symptoms, although because of the development of better drugs for these purposes and because of its numerous side-effects, it is rarely...

 has also been attempted with limited success.

While extreme weather conditions (cold and wind) increase the risk of frostbite it appears that certain individuals and population groups appear more resistant to milder forms of frostbite, perhaps due to longer term exposure and adaptation to cold weather environments. The "Hunter's Response
Hunter's Response
The Hunter's Response, also known as the Lewis wave, is a tendency for certain people in a cold environment, to periodically open to allow blood flow of capillaries of the extremities , when they might otherwise be constricted to preserve the body's core temperature...

" or Axon reflex
Axon reflex
An Axon reflex is a response brought on by peripheral nerve stimulation. Examples include Vasodilation originally described by Lewis as the "Hunter's Response" or autonomic reaction to loss of body heat in the extremities ..- See also :* Axon* Hunter's Response* Thermoregulation* Hypothermia*...

 are examples of this type of adaptation.

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