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Frostbite
Article Last Updated: May 15, 2008
AUTHOR AND EDITOR INFORMATION
Section 1 of 9  
Author: Robert A Schwartz, MD, MPH, Professor and Head of Dermatology, Professor of Medicine, Professor of Pediatrics, Professor of Pathology, Professor of Preventive Medicine and Community Health, UMDNJ-New Jersey Medical School
Robert A Schwartz is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American College of Physicians, and Sigma Xi
Coauthor(s):
Gregory E Rauscher, MD, Chairman Emeritus, Hackensack Medical Center; Professor, Department of Plastic Surgery, UMDNJ-New Jersey Medical School;
Cris Jagar, MD, Staff Physician, Department of Psychiatry, Saint Vincent Catholic Medical Centers
Editors: Neil Shear, MD, Professor and Chief of Dermatology, Professor of Medicine, Pediatrics and Pharmacology, University of Toronto Faculty of Medicine; Head of Dermatology, Sunnybrook Women's College Health Sciences Center and Women's College Hospital, Canada; Michael J Wells, MD, Associate Professor, Department of Dermatology, Texas Tech University Health Sciences Center; Jeffrey J Miller, MD, Associate Professor, Department of Dermatology, Penn State University, Milton S Hershey Medical Center; Catherine Quirk, MD, Clinical Assistant Professor, Department of Dermatology, Brown University; Dirk M Elston, MD, Director, Department of Dermatology, Geisinger Medical Center
Author and Editor Disclosure
Synonyms and related keywords:
frostnip, dermatitis congelationis, chilblains, trench foot
Background
Frostbite is an injury caused by exposure to cold temperatures. The temperature does not necessarily need to be below freezing for this injury to occur. The cold temperatures can cause ice crystals and clots to form and can result in poor perfusion to the face and the extremities, leading to dehydration and cell death. If the exposure continues, damage may occur to underlying blood vessels, nerves, and muscles. When patients receive medical care quickly, frostbite is often reversible because the injury is less severe. If treatment is delayed, patients may have long-term medical problems.
The following are other eMedicine articles on frostbite:
Pathophysiology
The extreme cold temperatures cause ice crystals to form in and around cells. Red blood cells and platelets also start to stick together, causing clots and ischemic damage in the extremities. Damage is also caused by reperfusion as the skin is warmed; therefore, if refreezing is a possibility, not warming the frostbite is important.
Frequency
United States
About 4800 cases of frostbite occur in the United States each year.
Mortality/Morbidity
- Peripheral circulation may be compromised, leading to gangrene and potential loss of the affected area.
- Exposure to the cold may lead to hypothermia.
- Long-term symptoms include paresthesia, sensitivity to cold, and faulty nail growth.
Race
All races are affected equally.
Sex
Both men and women are affected equally.
Age
People of all ages are affected.
- Elderly persons are more likely to be at risk because of other existing medical problems (eg, poor circulation).
- Young persons are also at higher risk because they may not be able to move themselves indoors.
History
Exposure to cold produces injuries that occur as a result of the human inability to adapt to cold.1 These injuries may be localized, systemic (as in hypothermia), or a combination of both. No serious damage usually occurs until tissue freezes. The mildest form of peripheral cold injury is termed frostnip. Chilblains is a more severe form of cold injury than frostnip and tends to occur after exposure to nonfreezing temperatures and damp conditions. Patients with frostbite often have multisystem injuries such as systemic hypothermia, blunt trauma, and substance abuse.
- Patients may have a history of prolonged exposure to cold weather. The exposure time and the temperature contribute to the depth of the frostbite and the amount of damage caused by the injury.
- Patients often have no feeling in the area of skin that is affected by frostbite; therefore, they may complain of paresthesia, numbness, or joint pain.
Physical
- Tissue that is affected by frostbite appears pale and is cold and hard. Common affected parts include a finger, a toe, an ear, the nose, or a cheek.
- Later, after warming, the skin becomes erythematous and edematous, and patients experience throbbing pain.
- The skin can be blue, or it can be necrotic or gangrenous.
- Within 6 hours, blisters appear and may be filled with clear fluid (indicating superficial damage) or with blood (indicating deep tissue damage).
- With superficial injuries, only the surface is frozen and deeper tissues are soft.
- With deep injury, the frozen part is hard and feels solid.
- Gangrene may appear and consists of 2 forms: wet and dry.
- Wet gangrene gives the skin a gray appearance and is soft.
- Dry gangrene gives the skin a black appearance and is hard.
Causes
Frostbite is caused by exposure to cold temperatures. The temperature does not necessarily need to be below freezing for injury to occur.
Other Problems to be Considered
Frostnip
Hypothermia
Acrocyanosis
Chilblains
Lab Studies
- No laboratory test exists for frostbite (it is a clinical diagnosis); however, a complete blood cell count with differential shows hemoconcentration due to dehydration.
- Liver function test results may be altered.
Imaging Studies
- Doppler studies, angiography, or MRI may be used to assess circulation.
- Doppler ultrasonography may be used to check the microvascular status of the affected feet and to define the extent of ultimate tissue loss.2
Other Tests
- An electrocardiogram may be useful because patients exposed to extreme cold may have irregular rhythms.
Histologic Findings
A histologic specimen of skin affected by frostbite can show a variety of findings. These findings include atrophy, necrosis, ice crystals, and an increased number of fibroblasts as the body attempts to repair the damage.
Medical Care
- Patients who are affected by frostbite may be affected by hypothermia and may require life-saving emergency interventions (eg, CPR, warming with intravenous fluids, oxygen). Tissue plasminogen activator (tPA) may also have a role in treatment of severe frostbite.3, 4 The effect of tPA and heparin in limb and digit preservation in severe frostbite patients has been studied. Intravenous tPA and heparin after rapid rewarming was judged safe and was found to considerably reduce predicted digit amputations. Patients with no response to thrombolytic therapy were identified as those with more than 24 hours of cold exposure, warm ischemia times greater than 6 hours, or evidence of multiple freeze-thaw cycles.
- Patients being treated for frostbite in the field must keep the affected area cold because the damage can be severe if the affected area is allowed to warm and then to refreeze.
- Use broad-spectrum antibiotics to prevent gangrene, if necessary, and to provide pain control with analgesics, especially during the process of rewarming.
- Administer tetanus toxoid.
- Optimum therapy is based on the rapid reversal of tissue freezing by rewarming in 104-110°F water and the institution of oral and topical antiprostaglandin therapy to limit the release of inflammatory mediators.
- Preventing infection and debriding the wound are important.
Surgical Care
Do not consider amputation until the affected tissues are clearly dead, which may take several weeks. The black surface tissue is shed, leaving healthy tissue underneath.
Deterrence/Prevention
- Wearing several layers of warm clothing and avoiding exposure to water and wind are the best ways to prevent frostbite.
- Covering the head is important because approximately 30% of heat loss occurs through the head.
- Wearing dry gloves, socks, and boots are important to conserve heat.
- Patients should maintain metabolic heat production by consuming ample food and fluids.
- Drugs and alcohol often play a role in developing frostbite because they impair judgment.
- People with Raynaud disease should be aware that they are more prone to frostbite because they may not feel the cold as much; they should take special care to prevent frostbite.
Complications
- Peripheral circulation may be compromised, leading to gangrene and potential loss of the affected area.
- Exposure to the cold may lead to hypothermia.
- Long-term complications include paresthesia, sensitivity to cold, and faulty nail growth.
- A third-degree ear burn was reported as a serious sequela of frostbite.5
Prognosis
- If patients receive medical attention before much damage has taken place, the damage is reversible and the patient will fully recover.
- If the damage is allowed to progress, the patient may develop long-lasting symptoms (eg, numbness, hypersensitivity to cold), or the patient may develop gangrene, and the affected area may have to be removed.
Patient Education
- Educate patients to dress appropriately for cold weather (even if they feel they do not need to) because the damage frostbite can cause may be severe and permanent. At high altitude, mountaineers should wear appropriate clothing, have the necessary equipment (eg, high-quality boots and mittens), use a competent guide, and have training in how to survive in cold weather.6 People should avoid wearing wet clothing and windy terrain, and should not remain in the same position for long periods.
- For excellent patient education resources, visit eMedicine's Environmental Exposures and Injuries Center. Also, see eMedicine's patient education article Frostbite.
Medical/Legal Pitfalls
- Failure to ensure that salvaging the affected area is not possible before amputating is a pitfall. Waiting as long as possible before amputation is advised but not at the cost of further deterioration of the patient's condition.
- Frostbite risks tissue or extremity loss.
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Frostbite excerpt Article Last Updated: May 15, 2008
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