Frostbite and frostnip

Definition

Frostbite is damage to the skin and other tissues caused by freezing. Frostnip is a mild form of this cold injury.

Description

Skin exposed to temperatures a little below 32°F (0°C) can take hours to freeze, but very cold skin can freeze in minutes or seconds. Nevertheless, under extreme conditions, even warm skin exposed to subzero temperatures and high wind chill factors can freeze rapidly. Air temperature, wind speed, humidity, and altitude all affect how cold the skin becomes. A strong wind can lower skin temperature considerably by dispersing the thin protective layer of warm air that surrounds the body. Wet clothing readily draws heat away from the skin because water is a potent conductor of heat. The evaporation of moisture on the skin also produces cooling. For these reasons, wet skin or clothing on a windy day can lead to frostbite even if the air temperature is above freezing.

The extent of permanent injury, however, is determined not by how cold the skin and the underlying tissues become but by how long they remain frozen. When skin is exposed to freezing temperatures, three things happen. The skin begins to freeze, causing ice crystal formation, damage to capillaries (the tiny blood vessels that connect the arteries and veins), and other changes that damage and eventually kill cells. Much of this harm occurs because the ice produces pressure changes that force water (crucial for cell survival) out of the cells.

Tissue hypoxia, or oxygen deficiency, occurs next as a survival mechanism in the body kicks in, causing the blood vessels in the hands, feet, and other extremities to narrow in response to cold. Among its many tasks, blood transfers body heat to the skin, which then dissipates the heat into the environment. Blood vessel narrowing is the body's way of protecting vital internal organs at the expense of the extremities by reducing heat flow away from the center of the body. However, blood also carries life-sustaining oxygen to the skin and other tissues, and narrowed vessels result in oxygen starvation. Narrowing also causes acidosis (an increase in tissue acidity) and increases blood viscosity (thickness). Ultimately, blood stops flowing through the capillaries) and blood clots form in the arterioles and venules (the smallest arteries and veins). Damage also occurs to the endothelial cells that line the blood vessels.

Hypoxia, blood clots, and endothelial damage lead, in turn, to the release of inflammatory mediators. These are substances that act as links in the inflammatory process, which promote further blood vessel damage, hypoxia, and cell destruction. Tissue damage is greatest when skin is exposed to freezing slowly or over a long period of time. More damage can occur when rewarming is slow or the affected area is warmed and refrozen.

Demographics

In North America, frostbite frequently occurs in Alaska, Canada, and the northern states, which have extremely cold winter temperatures. Frostbite, however, can occur almost anywhere, given the right conditions. Though there has been in the early 2000s a substantial decline in the number of frostbite cases in the United States, due to better winter clothing and footwear and greater public understanding of how to avoid cold-weather dangers, these cases are rising among the homeless who do not have adequate clothing or shelter. Frostbite has thus become an urban as well as a rural public health concern. The growing popularity of outdoor winter activities has also expanded the at-risk population.

Children are at a higher risk of experiencing frostbite and frostnip than adults because they experience heat loss from their skin more rapidly. Those children with disorders that affect circulation, such as diabetes, may be even more susceptible to frostbite and frostnip. Children who have had a recent injury, surgery, or blood loss are at risk, as well as teenagers who might be smoking , drinking alcohol, or taking beta-blockers for high blood pressure or a heart condition. Also, children who have had a frostbite injury in the past are more prone to having a recurrence in the same location. In addition, children from tropical climates may not be able to withstand cold temperatures as well as their cold-climate counterparts, making them more susceptible to frostbite and frostnip at higher temperatures.

Causes and symptoms

Causes

Skin damage from frostbite and frostnip occurs because of freezing, either by extremely cold weather, wet clothing in cold temperatures, or through chemical exposures, such as dry ice or highly compressed gases. Most children encounter frostbite when they participate in outdoor sports , camp in winter, get wet and cannot change their clothing immediately, or do not dress according to the weather conditions. Frostnip and frostbite are associated with ice crystal formation in the tissues.

Symptoms

In frostnip, no tissue destruction occurs and the ice crystals dissolve as soon as the skin is warmed. Frostnip affects areas such as the earlobes, cheeks, nose, fingers, and toes. The skin turns pale, and the person experiences numbness or tingling in the affected part until warming begins.

Frostbite, by contrast, has a range of severity. Most injuries affect the hands and feet, but about 10 percent of all frostbite cases affect the nose, cheeks, ears, and even the penis. Frostbite is classified by degree of injury (first, second, third, or fourth), or simply divided into two types, superficial (corresponding to first- or second-degree injury) and deep (corresponding to third- or fourth-degree injury). Frostnip is sometimes labeled a first-degree frostbite case.

Once frostbite sets in, the affected part begins to feel cold and, usually, numb. This condition is followed by a feeling of clumsiness. The skin turns white or yellowish. Many patients experience severe pain in the affected part during rewarming treatment and an intense throbbing pain that arises two or three days later and can last days or weeks. As the skin begins to thaw during treatment, edema (excess tissue fluid) often accumulates, causing swelling. In frostbite injuries of second-degree or higher, blisters appear. Third-degree cases produce deep, blood-filled blisters and a hard black eschar (scab). Fourth-degree frostbite penetrates below the skin to the muscles, tendons, nerves, and bones. Septicemia or blood poisoning and infection may also be present, as well as the possible need for amputation (the surgical removal of appendages such as fingers, toes, foot, or leg).

When to call the doctor

If a child's clothing has been wet for a long period of time or the child has been exposed to freezing temperatures, shows skin discoloration, and complains of feeling numb, the child should be seen by a doctor. In most cases, the child will be hospitalized to monitor the rewarming process and to do the necessary tests needed to determine the extent of the frostbite. Prolonged exposure to extreme temperatures can also produce hypothermia (lowered body temperature), which can be life threatening.

Diagnosis

Initial diagnosis is usually made based on the environmental conditions. Physical examination of the skin reveals that the skin is extremely cold and may have white, red, blue, or black areas on it. The patient may report feeling numb or a tingling sensation.

Frostbite diagnosis may also include conventional radiography (x rays), angiography (x-ray examination of the blood vessels using an injected dye to provide contrast), thermography (use of a heat-sensitive device for measuring blood flow), and other techniques for predicting the course of injury and identifying tissue that requires surgical removal. During the initial treatment period, however, a physician cannot judge how a case may progress. Diagnostic tests only become useful three to five days after rewarming, once the blood vessels have stabilized.

Treatment

Frostnip

Frostnipped fingers are helped by blowing warm air on them or holding them under one's armpits. Other frostnipped areas can be covered with warm hands. The injured areas should never be rubbed.

Frostbite

Emergency medical help should always be summoned whenever frostbite is suspected. While waiting for help to arrive, one should, if possible, remove wet or tight clothing and put on dry, loose clothing or cover with a blanket. Rubbing the area with snow or anything else is dangerous because it can cause tissue damage. The key to prehospital treatment is to avoid partial thawing and refreezing, which releases more inflammatory mediators and makes the injury substantially worse. For this reason, the affected part must be kept away from heat sources such as campfires and car heaters. Experts advise rewarming in the field only when emergency help will take more than two hours to arrive and refreezing can be prevented.

Because the outcome of a frostbite injury cannot be predicted at first, all hospital treatment follows the same routine. Treatment begins by rewarming the affected part for 15 to 30 minutes in water at a temperature of 104–108°F (40–42°C). This rapid rewarming halts ice crystal formation and dilates narrowed blood vessels. Aloe vera (which acts against inflammatory mediators) is applied to the affected part, which is then splinted, elevated, and wrapped in a dressing. Depending on the extent of injury, blisters may be debrided (cleaned by removing foreign material) or simply covered with aloe vera. A tetanus shot and, possibly, penicillin, are used to prevent infection, and the patient is given ibuprofen to combat inflammation. Narcotics are needed in most cases to reduce the excruciating pain that occurs as sensation returns during rewarming. Except when injury is minimal, treatment generally requires a hospital stay of several days, during which hydrotherapy and physical therapy are used to restore the affected part to health. Experts recommend a cautious approach to tissue removal and advise that 22 to 45 days must pass before a decision on amputation can safely be made.

Alternative treatment

Alternative practitioners suggest several kinds of treatment to speed recovery from frostbite after a person leaves the hospital. Bathing the affected part in warm water or using contrast hydrotherapy can help enhance circulation. Contrast hydrotherapy involves a series of hot and cold water applications. A hot compress (as hot as the patient can stand) is applied to the affected area for three minutes followed by an ice-cold compress for 30 seconds. These applications are repeated three times each, ending with the cold compress.

Nutritional therapy to promote tissue growth in damaged areas may also be helpful. Homeopathic and botanical therapies may also assist recovery from frostbite. Homeopathic Hypericum (Hypericum perforatum ) is recommended when nerve endings are affected (especially in the fingers and toes) and Arnica (Arnica montana ) is prescribed for shock. Cayenne pepper (Capsicum frutescens ) can enhance circulation and relieve pain. Drinking hot ginger (Zingiber officinale ) tea also aids circulation. Other possible approaches include acupuncture to avoid permanent nerve damage and oxygen therapy.

KEY TERMS

Acidosis —A disturbance of the balance of acid to base in the body causing an accumulation of acid or loss of alkali (base). Blood plasma normally has a pH of 7.35-7.45. Alkaline blood has a pH value greater than pH 7.45. When the blood pH value is less than 7.35, the patient is in acidosis. There are two types of acidosis: metabolic and respiratory. One of the most common causes of metabolic acidosis is an overdose of aspirin. Respiratory acidosis is caused by impaired breathing caused by conditions such as severe chronic bronchitis, bronchial asthma, or airway obstruction.

Amputation —Surgical removal of any portion of the body.

Angiography —Radiographic examination of blood vessels after injection with a radiopaque contrast substance or dye.

Arteriole —The smallest type of artery.

Capillaries —The tiniest blood vessels with the smallest diameter. These vessels receive blood from the arterioles and deliver blood to the venules. In the lungs, capillaries are located next to the alveoli so that they can pick up oxygen from inhaled air.

Hypothermia —A serious condition in which body temperature falls below 95°F (35 °C). It is usually caused by prolonged exposure to the cold.

Hypoxia —A condition characterized by insufficient oxygen in the cells of the body

Radiography —Examination of any part of the body through the use of x rays. The process produces an image of shadows and contrasts on film.

Thermography —Use of a heat-sensitive device for measuring blood flow.

Venules —The smallest veins.

Viscosity —Thickness of a liquid.

Prognosis

The rapid rewarming approach to frostbite treatment, pioneered in the 1980s, has proved to be much more effective than older methods in preventing tissue loss and amputation. A study of 56 first-, second-, and third-degree frostbite patients treated with rapid rewarming between 1982 and 1985 found that 68 percent recovered without tissue loss, 25 percent experienced some tissue loss, and 7 percent needed amputation. In a comparison group of 98 patients, treatment using older methods resulted in a tissue loss rate of nearly 35 percent and an amputation rate of nearly 33 percent. Although the comparison group included a higher proportion of second- and third-degree cases, the difference in treatment results was determined to be statistically significant.

The extreme throbbing pain that many frostbite sufferers endure for days or weeks after rewarming is not the only prolonged symptom of frostbite. During the first weeks or months, people often experience tingling, a burning sensation, or a sensation resembling shocks from an electric current. Other possible consequences of frostbite include skin-color changes, nail deformation or loss, joint stiffness and pain, hyperhidrosis (excessive sweating), and heightened sensitivity to cold. For everyone, a degree of sensory loss lasting at least four years, and sometimes a lifetime, is inevitable.

Prevention

With the appropriate knowledge and precautions, frostbite can be prevented even in the coldest and most challenging environments. Appropriate clothing and footwear are essential. To prevent heat loss and keep the blood circulating properly, clothing should be worn loosely and in layers. Covering the hands, feet, and head is also crucial for preventing heat loss. Children especially should wear hats that cover their heads and ears, mittens, and coats that are wind and water resistant. Wet clothing and footwear must be removed as quickly as possible and replaced with dry clothing and shoes.

Alcohol and drugs should be avoided because of their harmful effects on judgment and reasoning. Experts also warn against alcohol use and smoking in the cold because of the circulatory changes they produce.

Parental concerns

Parents should pay close attention to weather reports before sending children out to play or to take part in long-exposure outdoor activities such as sledding, skiing, and winter camping. Listening to winter driving warnings and road reports is also important before taking trips in the winter or in the mountains.

In addition, parents should keep a close eye on their children when the children play outdoors in winter around lakes, streams, and other water sources. Even older children and teenagers can slip on ice or snow and fall in. The risk of hypothermia and frostbite is too great to ignore. Sometimes, even a child's getting his or her shoes wet and then continuing to play in the cold can produce serious frostbite.

See also X rays.

Resources

BOOKS

Danzl, Daniel F. "Disturbances Due to Cold." In Conn's Current Therapy, ed. Robert E. Rakel. Philadelphia: W. B. Saunders Co., 1996.

McCauley, Robert L., et al. "Frostbite and Other Cold-Induced Injuries." In Wilderness Medicine: Management of Wilderness and Environmental Emergencies, ed. Paul S. Auerbach. St. Louis: Mosby, 1995.

WEB SITES

Bjerke, H. Scott, and Amit Tevar. "Frostbite." Available online at <www.emedicine.com/med/topic2815.htm> (accessed October 25, 2004).

"Frostbite Fact Sheet." Available online at <www.mckinley.uiuc.edu/handouts/frostbit/frostbit.html> (accessed October 25, 2004).

"Frostbite." KidsHealth for Parents. Available online at <www.kidshealth.org/parent/firstaid_safe/emergencies/frostbite.html> (accessed October 25, 2004).

Janie Franz Howard Baker

Frostbite and frostnip

Definition

Frostbite is localized tissue injury that occurs because of exposure to freezing or near freezing temperatures. Frostnip is a milder cold injury that does not cause tissue loss.

Description

In North America, frostbite is largely confined to Alaska, Canada, and the northern states. In recent years, there has been a substantial decline in the number of cases. This is probably for several reasons, including better winter clothing and footwear and greater public understanding of how to avoid cold-weather dangers. At the same time, the nature of the at-risk population has changed. Rising numbers of homeless people have made frostbite an urban as well as a rural public health concern. The growing popularity of outdoor winter activities has also expanded the at-risk population.

Causes & symptoms

Frostbite

Skin exposed to temperatures a little below the freezing mark can take hours to freeze, but very cold skin can freeze in minutes or seconds. Air temperature, wind speed, and moisture all affect how cold the skin becomes. A strong wind can lower skin temperature considerably by dispersing the thin protective layer of warm air that surrounds our bodies. Wet clothing readily draws heat away from the skin. The evaporation of moisture on the skin also produces cooling. For these reasons, wet skin or clothing on a windy day can lead to frostbite even if the air temperature is above the freezing mark.

The extent of permanent injury, however, is determined more by the length of time the skin is frozen than by how cold the skin and the underlying tissues become. Thus, homeless people and others whose self-preservation instincts may be clouded by alcohol or psychiatric illness face a greater risk of frostbite-related amputation. They are more likely to stay out in the cold when prudence dictates seeking shelter or medical attention. Alcohol also affects blood circulation in the extremities in a way that can increase the severity of injury, as does smoking . A review of 125 Saskatchewan frostbite cases found a tie to alcohol in 46% and to psychiatric illness in 17%. Driving in poor weather can also be dangerous: vehicular failure was a predisposing factor in 15% of the Saskatchewan cases.

Frostbite is classified by degree of injury (first, second, third, or fourth), or simply divided into two types, superficial (corresponding to first- or second-degree injury)

and deep (corresponding to third- or fourth-degree injury). Most frostbite injuries affect the feet or hands. The remaining 10% of cases typically involve the ears, nose, cheeks, or penis. Once frostbite sets in, the affected part begins to feel cold and, usually, numb; this is followed by a feeling of clumsiness. The skin turns white or yellowish. Many patients experience severe pain in the affected part during rewarming treatment and an intense throbbing pain that arises two or three days later and can last days or weeks. As the skin begins to thaw during treatment, edema often occurs, causing swelling in the area. In second-and higher-degree frostbite, blisters appear. Third-degree cases produce deep, blood-filled blisters and, during the second week, a hard black eschar (scab). Fourth-degree frostbite penetrates below the skin to the muscles, tendons, nerves, and bones. In severe cases of frostbite, the dead tissue can mummify and drop off. Affected areas are also more prone to infection.

Frostnip

Like frostbite, frostnip is associated with ice crystal formation in the tissues, but no tissue destruction occurs and the crystals dissolve as soon as the skin is warmed. Frostnip affects areas such as the earlobes, cheeks, nose, fingers, and toes. The skin turns pale and numb or tingly until warming begins.

Diagnosis

Frostbite diagnosis relies on a physical examination and may also include conventional radiography (x rays), angiography (x-ray examination of the blood vessels using an injected dye to provide contrast), thermography (use of a heat-sensitive device for measuring blood flow), and other techniques for predicting the course of injury and identifying tissue that requires surgical removal. During the initial treatment period, however, severity is difficult to judge. Diagnostic tests only become useful 3-5 days after rewarming, once the blood vessels have stabilized.

Treatment

Mechanical treatment

Frostnipped fingers are helped by blowing warm air on them or holding them under one's armpits. Other frostnipped areas can be covered with warm hands. The injured areas should never be rubbed.

By contrast, emergency medical help should always be sought whenever frostbite is suspected. While waiting for help to arrive, one should, if possible, remove wet or tight clothing and put on dry, loose clothing or wraps. A splint and padding are used to protect the injured area. Rubbing the area with snow or anything else is dangerous. The key to prehospital treatment is to avoid partial thawing and refreezing, which releases more mediators of inflammation and makes the injury substantially worse. For this reason, the affected part must be kept away from heat sources such as campfires and car heaters. Experts advise rewarming in the field only when emergency help will take more than two hours to arrive and refreezing can be prevented.

Because the outcome of a frostbite injury cannot be predicted at first, all hospital treatment follows the same route. Treatment begins by rewarming the affected part for 15-30 minutes in water at a temperature of 104-108°F (40-42.2°C). This rapid rewarming halts ice crystal formation and dilates narrowed blood vessels. Aloe vera (which acts against inflammatory mediators) is applied to the affected part, which is then splinted, elevated, and wrapped in a dressing. Milky blisters are debrided (cleaned by removing foreign material), and hemorrhagic (blood-filled) blisters are simply covered with aloe vera.

Hydrotherapy

Alternative practitioners suggest several kinds of treatment to speed recovery from frostbite after leaving the hospital. Bathing the affected part in warm water or using contrast hydrotherapy can enhance circulation. Contrast hydrotherapy involves a series of hot and cold water applications. A hot compress (as hot as the patient can stand) is applied to the affected area for three minutes followed by an ice-cold compress for 30 seconds. These applications are repeated three times each, ending with the cold compress. For patients who have been hospitalized with frostbite, hydrotherapy should only be performed after checking with a physician to ensure it is done correctly and does not aggravate the condition.

Homeopathy

Homeopathic Hypericum (Hypericum perforatum ) is recommended when nerve endings are affected (especially in the fingers and toes) and Arnica (Arnica montana ) is prescribed for shock and if there is accompanying blunt trauma to the frostbitten area.

Nutritional supplements

Cayenne pepper (Capsicum frutescens ) can enhance circulation and relieve pain. Drinking hot ginger (Zingiber officinale ) tea also aids circulation.

Other complementary therapies

Other possible approaches include acupuncture to avoid permanent nerve damage and oxygen therapy.

Allopathic treatment

In addition to the necessary rewarming and debridement described above, a tetanus shot and antibiotics may be used to prevent infection. The patient is given ibuprofen to combat inflammation. Narcotics are needed in most cases to reduce the excruciating pain that occurs as sensation returns during rewarming. Except when injury is minimal, treatment generally requires a hospital stay of several days, during which hydrotherapy and physical therapy are used to restore the affected part to health. Experts recommend a cautious approach to tissue removal, and advise that 22–45 days must pass before a decision on amputation can safely be made.

Expected results

The rapid rewarming approach to frostbite treatment, pioneered in the 1980s, has proved to be much more effective than older methods in preventing tissue loss and amputation. The extreme, throbbing pain that many frostbite sufferers endure for days or weeks after rewarming is not the only prolonged symptom of frostbite. During the first weeks or months, people often experience tingling, a burning sensation, or a sensation resembling shocks from an electric current. Other possible consequences of frostbite include changes of skin color, nail deformation or loss, joint stiffness and pain, hyperhidrosis (excessive sweating), and heightened sensitivity to cold. For everyone, a degree of sensory loss lasting at least four years—and sometimes a lifetime—is inevitable.

Prevention

With the appropriate knowledge and precautions, frostbite can be prevented even in the coldest and most challenging environments. Appropriate clothing and footwear are essential. To prevent heat loss and keep the blood circulating properly, clothing should be worn loosely and in layers. Covering the hands, feet, and head is also crucial for preventing heat loss. Outer garments need to be wind and water resistant, and wet clothing and footwear must be replaced as quickly as possible. Alcohol and drugs should be avoided because of their harmful effects on judgment and reasoning. Experts also warn against alcohol use and smoking in the cold because of the circulatory changes they produce. Paying close attention to the weather report before venturing outdoors and avoiding unnecessary risks such as driving in isolated areas during a blizzard are also important.

Resources

BOOKS

The Burton Goldberg Group. Alternative Medicine: The Definitive Guide. Tiburon, CA: Future Medicine Publishing, 1993.

Danzl, Daniel F. "Disturbances Due to Cold." In Conn's Current Therapy, edited by Robert E. Rakel. Philadelphia: W.B. Saunders, 1998.

McCauley, Robert L., et al. "Frostbite and Other Cold-Induced Injuries." In Wilderness Medicine: Management of Wilderness and Environmental Emergencies, edited by Paul S. Auerbach. St. Louis: Mosby, 1995.

PERIODICALS

Gill, Paul G., Jr. "Winning the Cold War." Outdoor Life (February 1993): 62+.

Phillips, David. "How Frostbite Performs Its Misery." Canadian Geographic (January-February 1995): 20+.

Reamy, Brian V. "Frostbite: Review and Current Concepts." Journal of the American Board of Family Practice (January-February 1998): 34-40. http://www.medscape.com/ABFP/JABFP/1998/v11.n01/fp1101.05.ream/fp1101.05.ream.html. (6 June 1998).

Winkelmann, Terry. "The Cold Facts about Frostbite." Stride (Winter 1997). http://www.stridemag.com/db_area/archives/1997/v2n4/frost.html. (6 June 1998).

Judith Turner

Frostbite and Frostnip

Definition

Frostbite is the term for damage to the skin and other tissues caused by freezing. Frostnip is a mild form of cold injury.

Description

In North America, frostbite is largely confined to Alaska, Canada, and the northern states. Recent years have witnessed a substantial decline in the number of cases, probably for several reasons, including better winter clothing and footwear and greater public understanding of how to avoid cold-weather dangers. At the same time, the nature of the at-risk population has changed as rising numbers of homeless people have made frostbite an urban as well as a rural public health concern. The growing popularity of outdoor winter activities has also expanded the at-risk population.

Causes and symptoms

Frostbite

Skin exposed to temperatures a little below the freezing mark can take hours to freeze, but very cold skin can freeze in minutes or seconds. Air temperature, wind speed, and moisture all affect how cold the skin becomes. A strong wind can lower skin temperature considerably by dispersing the thin protective layer of warm air that surrounds our bodies. Wet clothing readily draws heat away from the skin because water is a potent conductor of heat. The evaporation of moisture on the skin also produces cooling. For these reasons, wet skin or clothing on a windy day can lead to frostbite even if the air temperature is above the freezing mark.

The extent of permanent injury, however, is determined not by how cold the skin and the underlying tissues become but by how long they remain frozen. Consequently, homeless people and others whose self-preservation instincts may be clouded by alcohol or psychiatric illness face a greater risk of frostbite-related amputation because they are more likely to stay out in the cold when prudence dictates seeking shelter or medical attention. Alcohol also affects blood circulation in the extremities in a way that can increase the severity of injury (as does smoking ). A review of 125 Saskatchewan frostbite cases found a tie to alcohol in 46% and to psychiatric illness in 17%. Other risk factors identified by researchers include inadequate clothing, previous cold injury, fatigue, wound infection, atherosclerosis (an arterial disease), and diabetes. Driving in poor weather can also be dangerous: vehicular failure was a predisposing factor in 15% of the Saskatchewan cases.

Three nearly simultaneous physiological processes underlie frostbite injury: tissue freezing, tissue hypoxia, and the release of inflammatory mediators. Tissue freezing causes ice crystal formation and other changes that damage and eventually kill cells. Much of this harm occurs because the ice produces pressure changes that cause water (crucial for cell survival) to flow out of the cells. Tissue hypoxia (oxygen deficiency) occurs when the blood vessels in the hands, feet, and other extremities narrow in response to cold. Among its many tasks, blood transfers body heat to the skin, which then dissipates the heat into the environment. Blood vessel narrowing is the body's way of protecting vital internal organs at the expense of the extremities by reducing heat flow away from the core. However, blood also carries life-sustaining oxygen to the skin and other tissues, and narrowed vessels result in oxygen starvation. Narrowing also causes acidosis (an increase in tissue acidity) and increases blood viscosity (thickness). Ultimately, blood stops flowing through the capillaries (the tiny blood vessels that connect the arteries and veins) and blood clots form in the arterioles and venules (the smallest arteries and veins). Damage also occurs to the endothelial cells that line the blood vessels. Hypoxia, blood clots, and endothelial damage lead, in turn, to the release of inflammatory mediators (substances that act as links in the inflammatory process), which promote further endothelial damage, hypoxia, and cell destruction.

Frostbite is classified by degree of injury (first, second, third, or fourth), or simply divided into two types, superficial (corresponding to first- or second-degree injury) and deep (corresponding to third- or fourth-degree injury). Most frostbite injuries affect the feet or hands. The remaining 10% of cases typically involve the ears, nose, cheeks, or penis. Once frostbite sets in, the affected part begins to feel cold and, usually, numb; this is followed by a feeling of clumsiness. The skin turns white or yellowish. Many patients experience severe pain in the affected part during rewarming treatment and an intense throbbing pain that arises two or three days later and can last days or weeks. As the skin begins to thaw during treatment, edema (excess tissue fluid) often accumulates, causing swelling. In second- and higher-degree frostbite, blisters appear. Third-degree cases produce deep, bloodfilled blisters and, during the second week, a hard black eschar (scab). Fourth-degree frostbite penetrates below the skin to the muscles, tendons, nerves, and bones. In severe cases of frostbite the dead tissue can mummify and drop off. Infection is also a possibility.

Frostnip

Like frostbite, frostnip is associated with ice crystal formation in the tissues, but no tissue destruction occurs and the crystals dissolve as soon as the skin is warmed. Frostnip affects areas such as the earlobes, cheeks, nose, fingers, and toes. The skin turns pale and one experiences numbness or tingling in the affected part until warming begins.

Diagnosis

Frostbite diagnosis relies on a physical examination and may also include conventional radiography (x rays), angiography (x-ray examination of the blood vessels using an injected dye to provide contrast), thermography (use of a heat-sensitive device for measuring blood flow), and other techniques for predicting the course of injury and identifying tissue that requires surgical removal. During the initial treatment period, however, a physician cannot judge how a case will progress. Diagnostic tests only become useful three to five days after rewarming, once the blood vessels have stabilized.

Treatment

Frostbite

Emergency medical help should always be summoned whenever frostbite is suspected. While waiting for help to arrive, one should, if possible, remove wet or tight clothing and put on dry, loose clothing or wraps. A splint and padding are used to protect the injured area. Rubbing the area with snow or anything else is dangerous. The key to prehospital treatment is to avoid partial thawing and refreezing, which releases more inflammatory mediators and makes the injury substantially worse. For this reason, the affected part must be kept away from heat sources such as campfires and car heaters. Experts advise rewarming in the field only when emergency help will take more than two hours to arrive and refreezing can be prevented.

Because the outcome of a frostbite injury cannot be predicted at first, all hospital treatment follows the same route. Treatment begins by rewarming the affected part for 15-30 minutes in water at a temperature of 104-108 °F (40-42.2 °C). This rapid rewarming halts ice crystal formation and dilates narrowed blood vessels. Aloe vera (which acts against inflammatory mediators) is applied to the affected part, which is then splinted, elevated, and wrapped in a dressing. Depending on the extent of injury, blisters may be debrided (cleaned by removing foreign material) or simply covered with aloe vera. A tetanus shot and, possibly, penicillin, are used to prevent infection, and the patient is given ibuprofen to combat inflammation. Narcotics are needed in most cases to reduce the excruciating pain that occurs as sensation returns during rewarming. Except when injury is minimal, treatment generally requires a hospital stay of several days, during which hydrotherapy and physical therapy are used to restore the affected part to health. Experts recommend a cautious approach to tissue removal, and advise that 22-45 days must pass before a decision on amputation can safely be made.

Frostnip

Frostnipped fingers are helped by blowing warm air on them or holding them under one's armpits. Other frostnipped areas can be covered with warm hands. The injured areas should never be rubbed.

Alternative treatment

Alternative practitioners suggest several kinds of treatment to speed recovery from frostbite after leaving the hospital. Bathing the affected part in warm water or using contrast hydrotherapy can help enhance circulation. Contrast hydrotherapy involves a series of hot and cold water applications. A hot compress (as hot as the patient can stand) is applied to the affected area for three minutes followed by an ice cold compress for 30 seconds. These applications are repeated three times each, ending with the cold compress. Nutritional therapy to promote tissue growth in damaged areas may also be helpful. Homeopathic and botanical therapies may also assist recovery from frostbite. Homeopathic Hypericum (Hypericum perforatum) is recommended when nerve ending are affected (especially in the fingers and toes) and Arnica (Arnica montana) is prescribed for shock. Cayenne pepper (Capsicum frutescens ) can enhance circulation and relieve pain. Drinking hot ginger (Zingiber officinale ) tea also aids circulation. Other possible approaches include acupuncture to avoid permanent nerve damage and oxygen therapy.

Prognosis

The rapid rewarming approach to frostbite treatment, pioneered in the 1980s, has proved to be much more effective than older methods in preventing tissue loss and amputation. A study of 56 first-, second-, and third-degree frostbite patients treated with rapid rewarming in 1982–85 found that 68% recovered without tissue loss, 25% experienced some tissue loss, and 7% needed amputation. In a comparison group of 98 patients, treatment using older methods resulted in a tissue loss rate of nearly 35% and an amputation rate of nearly 33%. Although the comparison group included a higher proportion of second- and third-degree cases, the difference in treatment results was determined to be statistically significant.

The extreme throbbing pain that many frostbite sufferers endure for days or weeks after rewarming is not the only prolonged symptom of frostbite. During the first weeks or months, people often experience tingling, a burning sensation, or a sensation resembling shocks from an electric current. Other possible consequences of frostbite include skin—color changes, nail deformation or loss, joint stiffness and pain, hyperhidrosis (excessive sweating), and heightened sensitivity to cold. For everyone, a degree of sensory loss lasting at least four years—and sometimes a lifetime—is inevitable.

Prevention

With the appropriate knowledge and precautions, frostbite can be prevented even in the coldest and most challenging environments. Appropriate clothing and footwear are essential. To prevent heat loss and keep the blood circulating properly, clothing should be worn loosely and in layers. Covering the hands, feet, and head is also crucial for preventing heat loss. Outer garments need to be wind and water resistant, and wet clothing and footwear must be replaced as quickly as possible. Alcohol and drugs should be avoided because of their harmful effects on judgment and reasoning. Experts also warn against alcohol use and smoking in the cold because of the circulatory changes they produce. Paying close attention to the weather report before venturing outdoors and avoiding unnecessary risks such as driving in isolated areas during a blizzard are also important.

Resources

PERIODICALS

Reamy, Brian V. "Frostbite: Review and Current Concepts." Journal of the American Board of Family Practice January-February 1998: 34-40.

Frostbite

Stages of frostbite

Treatment for frostbite

Resources

Frostbite is the freezing of human or animal tissue. It occurs when body parts, most commonly the fingers, toes, and the tips of ears and the nose, are exposed for long periods to the cold. Frostbite is a direct result of limited blood circulation. The blood is the body’s internal heating system; it carries heat to the body tissues. But prolonged exposure to the cold can constrict blood vessels, causing blood circulation within tissues to slow down. When tissues are deprived of the warmth of circulating blood, ice crystals can then form, leading to tissue death and loss of the affected body parts.

Stages of frostbite

There are three degrees, or stages, of frostbite: frostnip, superficial frostbite, and deep frostbite. Frostnip is the least serious form of frostbite; deep frostbite the most serious. If frostnip goes untreated, it can quickly progress to the more serious forms. Recognizing and treating the first signs of frostnip may prevent the development of the more serious forms of frostbite.

Frostnip is the warning sign of frostbite. In frost-nip, the skin reddens then turns white. The person may also experience numbness in the affected area. The treatment for frostnip is simple—get the person out of the cold and gently warm the affected area. The warming procedure does not require special equipment; if the hands are affected, placing the hands under the armpits may be sufficient; if the fingers are affected, blowing warm air on them should be enough.

The next two stages of frostbite may set in if frostnip is not treated promptly. In superficial frostbite, only the top layer of the skin is frozen. It becomes rigid, but the layers beneath the frozen layer are soft. The affected area appears white. In deep frostbite, the deeper layers of skin and tissue are frozen. The area feels rigid, and if the area is gently pressed no “give” or softness can be felt. The color of the affected area progresses from white to a grayish-yellow color and

finally to a grayish blue color. In severe cases of deep frostbite, muscles, bones, and even the organs may become frozen.

Treatment for frostbite

People with superficial or deep frostbite should be taken to a hospital immediately. If transport to a hospital is delayed, the following measures can be taken to prevent further injury:

• Keep the person warm. Try to get the person indoors to a heated environment and cover with blankets, if available.
• Don’t let the person smoke or drink alcohol. Both nicotine and alcohol can further constrict blood vessels and decrease blood circulation.
• Don’t rub the affected area.

Most experts advise people not to rewarm or thaw frostbitten areas themselves. If thawing is not done properly, serious consequences such as loss of the affected area can result. For instance, thawing a frostbitten area by holding the affected area close to a campfire or in front of an open oven door can burn already-damaged tissues. Rubbing a frostbitten area with snow or ice is also not recommended. This will only cause more ice crystals to form in frozen tissue.

Rewarming should only be performed by trained medical personnel. The rewarming should be gradual. The affected part of the body (or sometimes the entire person if the affected area is extensive) is submerged in a tub of warm water. The water is usually between 100-106°F (37.7-41.1°C). Pain is a sign that thawing is taking place. During rewarming, it is extremely important that the person remain as still as possible. Motion can cause still-frozen tissue to break, which may injure delicate newly thawed tissues.

KEY TERMS

Deep frostbite— a serious condition in which the deeper tissues of the body freeze. Deep frostbite is characterized by a grayish-yellow appearance that progresses to grayish white. Both the top layer of skin and deeper tissues are rigid to the touch.

Frostnip— the “warning sign” of frostbite, characterized by a white appearance and numbness.

Superficial frostbite— sometimes referred to as “frostbite”; the freezing of the top layer of skin. Superficial frostbite is characterized by a white appearance and rigidity of the top layer of skin.

After rewarming, the affected area is sometimes loosely wrapped in sterile cloth. The person is carefully monitored for infection and signs of restored circulation. If the area does not show renewed circulation or if the area becomes infected, amputation is sometimes performed. Amputation is necessary to prevent infection from spreading into other areas of the body.

Hospitals in Alaska have established guidelines for the assessment and treatment of frostbite. Many physicians and other health care personnel have also made helpful observations about the incidence of frostbite that may prevent some cases. One physician noted a sharp increase in the incidence of frostbite affecting the ears in young male patients in the late 1970s and 1980s compared to the 1960s and early 1970s. This physician surmised that in the 1960s and 1970s, men wore their hair longer, thus protecting their ears from frostbite, but the shorter hairstyles of the 1980s exposed ears to the elements. Another physician noted a correlation between snorting cocaine and frostbite affecting the tip of the nose. Like the cold, cocaine also leads to constriction of the mucous membranes and the arteries in the nose. A person using cocaine may develop frostbite faster than a person who isn’t. Yet another observation is a correlation between frostbite of the feet and the wearing of tennis and running shoes. In cold climates especially, proper footwear is essential to prevent frostbite.

In addition to these guidelines, other measures can be taken. When working or playing outdoors, refrain from drinking alcohol or smoking. Always wear proper clothing and take special care of the areas most vulnerable to cold exposure: the ears, tip of the nose, fingers, and toes. When any part of your body starts to feel numb, go indoors to warm that part immediately. These commonsense tactics should ensure safety when the temperature drops.

See also Circulatory system; Integumentary system; Nerve growth factor; Organ.

Resources

BOOKS

Grant, Henry, et. al. Brady Emergency Care. 6th ed. Englewood Cliffs: Prentice Hall, 1990, pp. 566-568.

PERIODICALS

Mills, William J. “Summary of Treatment of the Cold Injured Patient: Frostbite.” Alaska Medicine 35, no. 1: pp. 61-66.

OTHER

eMedicine. <http://www.emedicine.com/emerg/topic209.htm= (accessed November 24, 2006).

U.S. National Library of Medicine; National Institutes of Health: MedLine Plus. “Frostbite” <http://www.nlm.nih.gov/medlineplus/ency/article/000057.htm= (accessed November 24, 2006).

FROSTBITE

DEFINITION

Frostbite is damage to the skin and other tissue caused by freezing. The term frostnip is sometimes used for a mild form of frostbite.

DESCRIPTION

Frostbite is caused by exposure to temperatures well below freezing (32°F or 0°C). Dry conditions contribute to frostbite damage. At temperatures closer to freezing, frostnip is more likely to occur. Humid air is also more likely to produce frostnip than frostbite.

In North America, frostbite occurs most frequently in Alaska, Canada, and the northernmost regions of the United States. In recent years, the number of cases of frostbite and frostnip have decreased considerably. One reason for this change is that the general public is better educated about the dangers of these two conditions. Also, warmer clothing and footwear are generally available.

The one group of people among whom frostbite and frostnip has increased are the homeless. Homeless people often have no place to go when the temperature drops. The growing popularity of outdoor sports has also increased the number of people at risk for frostbite and frostnip.

Frostbite: Words to Know

Amputation:

A surgical procedure in which an arm, leg, hand, or foot is removed.

Contrast hydrotherapy:

A procedure in which a series of hot and cold water applications is applied to an injured area.

Narcotic:

A drug that relieves pain and induces sleep.

CAUSES

The human body can withstand temperatures a little below freezing for hours before freezing. However, exposure to very cold temperatures can freeze skin in minutes or even seconds. Air temperature, wind speed, and moisture all affect the rate at which the body loses heat. For example, wet clothing increases the risk for frostbite. Water absorbs heat quickly and efficiently. It causes the body to cool off very quickly.

The permanent damage done to the body depends more on how long it was exposed to cold temperatures than on how cold it got. This fact explains why so many people are injured by frostbite. The overnight temperature may not drop very low, but homeless people are forced to remain outside for hours at a time. This long exposure to even mildly cold temperatures can cause frostbite.

Several factors increase a person's risk for frostbite. Alcohol use is a major risk factor for frostbite. Alcohol reduces blood circulation. It causes the body to cool off quickly. It also impairs ones judgement. A person who has been drinking may not notice how cold it is, or realize that he or she is getting frostbite, and stay outdoors even after injury has occured. In one study

of frostbite injuries, nearly half occurred among people who had been drinking. Other factors contributing to the risk for frostbite include:

• Psychiatric illness
• Inadequate clothing
• Fatigue
• Infection from a wound
• Atherosclerosis (see atherosclerosis entry)
• Diabetes (see diabetes mellitus entry)
• Previous injuries due to cold temperatures

SYMPTOMS

Most frostbite injuries affect the feet or hands. About 10 percent of all cases involve the ears, nose, cheeks, or penis. The first symptoms of frostbite are a feeling of cold and numbness in the affected body part. The skin then begins to turn white or yellowish. Many patients experience severe pain in the affected part.

Symptoms continue as the body begins to warm up. The pain returns or continues during this period. It may last for days or weeks. As the skin begins to thaw, fluids may collect, causing swelling of the affected area. In more serious cases, deep, blood-filled blisters may form. In the most severe cases of frostbite, the muscles, tendons, nerves, and bones may also be damaged by cold. In such cases, dead tissue may drop off or become infected.

The symptoms of frostnip are less severe. The skin may turn pale. Numbness and tingling are likely to occur in the affected area.

DIAGNOSIS

A first diagnosis of frostbite or frostnip can usually be made on the basis of environmental conditions. A person found unconscious in freezing weather may be presumed to be at risk for frostbite. Physical examination of the skin often confirms this diagnosis. The skin tends to be cold, hard, white, and numb if frostbite is present. As it warms, the skin becomes red, swollen, and painful. Doctors usually classify the extent of frostbite as being superficial or deep. The prognosis for all forms of frostbite is often not clear for many days.

TREATMENT

Frostbite is a potentially serious problem that requires emergency medical treatment. First aid involves replacing wet clothing with warm, dry clothing or blankets. A splint or padding can be used to protect the injured area. Observers should not attempt to warm the patient in the field. The re-warming procedure should take place under controlled conditions in the hospital.

The outcome of a frostbite injury cannot be predicted in the first few days. For that reason, the same treatment is used with all patients. Treatment involves re-warming of the affected area at a temperature of 104° to 108°F (40° to 42°C). The injury is treated with aloe vera and splinted, wrapped, and elevated.

Injections of tetanus vaccine and penicillin may be given. These injections protect the patient against infection. An anti-inflammatory drug, such as aspirin or ibuprofen, may also be given. In some cases, narcotics may be needed to treat the severe pain that occurs with deep frostbite.

In the most serious cases, frostbite may cause extensive tissue damage. Amputation (removal) of an arm, leg, hand, or foot may be necessary. A decision to take this action is usually delayed as long as possible to see if the damaged tissue will recover.

Alternative Treatment

Alternative treatments of frostbite should not be attempted until the patient has received medical care. After that point, methods are available for shortening the recovery period. One such method is contrast hydrotherapy. In contrast hydrotherapy, a series of hot and cold water applications is used on the affected area.

Some homeopathic remedies suggested for frostbite recovery include Hypericum and Arnica (pronounced AHR-nih-kuh). Circulation may be improved by drinking hot ginger tea or taking small amounts of cayenne pepper.

PROGNOSIS

A new approach to frostbite treatment was developed in the 1980s. The major emphasis in this method is to re-warm the body as quickly as possible. This method has proved to be very successful. In one study, about twothirds of patients with superficial frostbite recovered completely without tissue loss. The success rate using older methods was only about 35 percent (or about one-third of patients).

The most serious consequence of frostbite may be amputation. People who do not require amputation may still experience long-term symptoms. These symptoms include extreme throbbing pain, a burning sensation or tingling feelings, color changes of the skin, changes in the shape of nails or loss of nails, joint stiffness, excessive sweating, and a heightened sensitivity to cold.

PREVENTION

Frostbite typically occurs when a person is exposed to extreme weather conditions, such as very cold temperatures and high winds. Anyone who expects to encounter these conditions should prepare for them by dressing warmly and staying outside no longer than necessary. Outer garments should be wind- and water-resistant. If clothing becomes wet, it should be replaced as quickly as possible. Alcohol, drugs, and smoking should be avoided if one will be exposed to the elements for long periods of time.

Some groups of people, such as the homeless, may find it more difficult to avoid frostbite. They may not understand the need for protection from the cold or, more often, they do not have the resources to buy the clothing or shelter needed for protection. In such cases, the community may be responsible for providing the protection that homeless people are not able to provide for themselves.

See also: Hypothermia.

FOR MORE INFORMATION

Books

The Burton Goldberg Group. Alternative Medicine: The Definitive Guide. Puyallup, WA: Future Medicine Publishing, 1993.

McCauley, Robert L., et al., "Frostbite and Other Cold-Induced Injuries," in Paul S. Auerbach, ed. Wilderness Medicine: Management of Wilderness and Environmental Emergencies. St. Louis: Mosby, 1995.

Wilkerson, James A., and Cameron C. Bangs, eds. Hypothermia, Frostbite, and Other Cold Injuries: Prevention, Recognition and Pre-Hospital Treatment. Seattle, WA: Mountaineers Books, 1986.

Periodicals

Gill, Paul G., Jr., "Winning the Cold War." Outdoor Life (February 1993): pp. 62+.