Frostbite is aninjury toskin or other living tissue that is allowed tofreeze,[1] especially affecting thefingers,toes,nose,ears,cheeks andchin.[6] Most often, frostbite occurs in the hands and feet,[7][8] often preceded byfrostnip, a paling or reddening of a body part as its blood vessels constrict thattingles, feels very cold, or simply feelsnumb.[9][2][10] This may be followed by the clumsiness and white or bluish, waxy-looking skin that evidence full-blown frostbite.[1][11] Swelling orblistering may occur following treatment.[1] Complications may includehypothermia orcompartment syndrome.[2][1]
People who are exposed to low temperatures for prolonged periods, such as winter sports enthusiasts, military personnel, and thehomeless, are at greatest risk.[7][1] Other risk factors include drinkingalcohol,smoking,mental health problems, certain medications, and prior injuries due to cold.[1] The underlying mechanism involves injury from ice crystals andblood clots in smallblood vessels following thawing.[1] Diagnosis is based on symptoms.[3] Severity may be divided into superficial (first and second degree) and deep (third and fourth degree).[2] Abone scan orMRI may help in determining the extent of injury.[1]
Prevention consists of wearing proper, fully-covering clothing, avoiding low temperatures and wind, maintaininghydration and nutrition, and sufficient physical activity to maintaincore temperature without exhaustion.[2] Treatment is by rewarming, immersion in warm water (near body temperature), or body contact, and should be done only when a consistent temperature can be maintained so that refreezing is not a risk.[2][1] Rapid heating or cooling should be avoided since it could potentially cause burning or heart stress.[12] Rubbing or applying force to the affected areas should be avoided as it may cause further damage such asabrasions.[2] The use ofibuprofen andtetanus toxoid is recommended for pain relief or to reduce swelling or inflammation.[1] For severe injuries,iloprost orthrombolytics may be used.[1] Surgery, includingamputation, is sometimes necessary.[1][2]
Evidence of frostbite occurring in humans dates back 5,000 years.[1] Evidence was documented in a pre-Columbian mummy discovered in the Andes.[7] The number of annual cases of frostbite is unknown.[5] Rates may be as high as 40% a year among those whomountaineer.[1] The most common age group affected is those 30 to 50 years old.[4] Frostbite has also played an important role in a number of military conflicts.[1] Its first formal description was in 1813 byDominique Jean Larrey, a physician inNapoleon's army, during itsinvasion of Russia.[1] Frostbite reports were largely military until the late 1950s.[13]
Areas that are usually affected include cheeks, ears, nose and fingers and toes. Frostbite is often preceded by frostnip.[2][14] The symptoms of frostbite progress with prolonged exposure to cold. Historically, frostbite has been classified by degrees according to skin and sensation changes, similar to burn classifications. However, the degrees do not correspond to the amount of long-term damage.[15] A simplification of this system of classification is superficial (first or second degree) or deep injury (third or fourth degree).[16]
First-degree frostbite is superficial, surface skin damage that is usually not permanent.
Early on, the primary symptom is loss of feeling in the skin. In the affected areas, the skin is numb, waxy, and possibly swollen, with a reddened border.
In the weeks after injury, the skin's surface may slough off.[15]
Third degree frostbite developing. Doppler arterial ultrasound showed adequate perfusion to the foot with no blood flow to the toes. Gangrene was still demarcating, i.e., separating dead from living tissue.
In fourth-degree frostbite, structures below the skin, like muscles, tendon, and bone, are involved.
Early symptoms include a colorless appearance of the skin, a hard texture, and painless rewarming.
Later, the skin becomes black andmummified. The amount of permanent damage can take one month or more to determine.Autoamputation can occur after two months.[15]Fourth-degree frostbite in a homeless patient five days after freezing conditions. Patient developedtrench foot and was unable to properly dry feet.Plantar surface of frostbitten feet five days after a freeze. Patient was homeless with poor footwear.
The major risk factor for frostbite is exposure to cold through geography, occupation and/or recreation. Inadequate clothing and shelter are major risk factors. Frostbite is more likely when the body's ability to produce or retain heat is impaired. Physical, behavioral, and environmental factors can all contribute to the development of frostbite. Immobility and physical stress (such as malnutrition or dehydration) are also risk factors.[7] Disorders and substances that impair circulation contribute, includingdiabetes,Raynaud's phenomenon,tobacco andalcohol use.[16] Homeless individuals and individuals with some mental illnesses may be at higher risk.[7]
In frostbite, cooling of the body causes narrowing of the blood vessels (vasoconstriction). Prolonged exposure to temperatures below −2 °C (28 °F) may cause ice crystals to form in the tissues, and prolonged exposure to temperatures below −4 °C (25 °F) may cause ice crystals to form in the blood.[18] Ice crystals can damage small blood vessels at the site of injury.[16] Typically, prolonged exposure to temperatures below −0.55 °C (31.01 °F) may cause frostbite.[19]
Rewarming, though vital, causes tissue damage throughreperfusion injury, which involvesvasodilation, swelling (edema), and poor blood flow (stasis).Platelet aggregation is another possible mechanism of injury. Blisters and spasm of blood vessels (vasospasm) can develop after rewarming.[16]
The process of frostbite differs from the process ofnon-freezing cold injury (NFCI). In NFCI, temperature in the tissue decreases gradually. This slower temperature decrease allows the body to try to compensate through alternating cycles of closing and opening blood vessels (vasoconstriction andvasodilation). If this process continues, inflammatorymast cells act in the area. Smallclots (microthrombi) form and can cut off blood to the affected area (known asischemia) and damage nerve fibers. Rewarming causes a series of inflammatory chemicals such asprostaglandins to increase localized clotting.[20]
The pathological mechanism by which frostbite causes body tissue injury can be characterized by four stages: Prefreeze, freeze-thaw, vascular stasis, and the late ischemic stage.[21]
Prefreeze phase: involves the cooling of tissues without ice crystal formation.[21]
Freeze-thaw phase: ice-crystals form, resulting in cellular damage and death.[21]
Vascular stasis phase: marked by bloodcoagulation or the leaking of blood out of the vessels.[21]
Late ischemic phase: characterized by inflammatory events,ischemia and tissue death.[21]
Frostbite is diagnosed on the basis of signs and symptoms as described above, and bypatient history. Other conditions that can have a similar appearance or occur at the same time include:
Frostnip, a precursor to frostbite with a similar appearance, but without ice crystal formation in the skin. Whitening of the skin and numbness reverse quickly after rewarming.
Trench foot, damage to nerves and blood vessels that results from exposure to cold wet (non-freezing) conditions.[22] This is reversible if treated early.
Pernio or chilblains, inflammation of the skin from exposure to wet, cold (non-freezing) conditions. They can appear as various types of ulcers and blisters.[15]
Bullous pemphigoid, a condition that causes itchy blisters over the body that can mimic frostbite.[23] It does not require exposure to cold to develop.
Levamisole toxicity, avasculitis that can appear similar to frostbite.[23] It is caused by contamination of cocaine bylevamisole. Skin lesions can look similar those of frostbite, but do not require cold exposure to occur.
People who havehypothermia often have frostbite as well.[15] Since hypothermia is life-threatening this should be treated first.Technetium-99 orMR scans are not required for diagnosis, but might be useful for prognostic purposes.[24]
TheWilderness Medical Society recommends covering the skin and scalp, taking in adequate nutrition, avoiding constrictive footwear and clothing, and remaining active without causing exhaustion. Supplemental oxygen may also be of use at high elevations. Repeated exposure to cold water makes people more susceptible to frostbite.[25] Additional measures to prevent frostbite include:[2]
Avoiding temperatures below −23 °C (-9 °F)
Avoiding moisture, including in the form ofsweat and/or skinemollients
Avoiding alcohol and drugs that impair circulation or natural protective responses
Layering clothing
Using chemical or electric warming devices
Recognizing early signs of frostnip and frostbite[2]
Individuals with frostbite or potential frostbite should go to a protected environment and get warm fluids. If there is no risk of re-freezing, the extremity can be exposed and warmed in the underarm of a companion or the groin. If the area is allowed to refreeze, there can be worse tissue damage. If the area cannot be reliably kept warm, the person should be brought to a medical facility without rewarming the area. Rubbing the affected area can also increase tissue damage.Aspirin andibuprofen can be given in the field[7] to prevent clotting and inflammation. Ibuprofen is often preferred to aspirin because aspirin may block a subset ofprostaglandins that are important in injury repair.[26]
The first priority in people with frostbite should be to assess forhypothermia and other life-threatening complications of cold exposure. Before treating frostbite, thecore temperature should be raised above 35 °C. Oral orintravenous (IV) fluids should be given.[7]
Other considerations for standard hospital management include:
If the area is still partially or fully frozen, it should be rewarmed in the hospital with a warm bath withpovidone iodine orchlorhexidineantiseptic.[7] Active rewarming seeks to warm the injured tissue as quickly as possible without burning. The faster tissue is thawed, the less tissue damage occurs.[27] According to Handford and colleagues, "The Wilderness Medical Society and State of Alaska Cold Injury Guidelines recommend a temperature of 37–39 °C, which decreases the pain experienced by the patient whilst only slightly slowing rewarming time." Warming takes 15 minutes to 1 hour. The faucet should be left running so the water can circulate.[28] Rewarming can be very painful, so pain management is important.[7]
People with potential for large amputations and who present within 24 hours of injury can be givenTPA withheparin.[1] These medications should be withheld if there are any contraindications.Bone scans orCT angiography can be done to assess damage.[29]
Blood vessel dilating medications such asiloprost may prevent blood vessel blockage.[7] This treatment might be appropriate in grades 2–4 frostbite, when people get treatment within 48 hours.[29] In addition to vasodilators,sympatholytic drugs can be used to counteract the detrimental peripheralvasoconstriction that occurs during frostbite.[30]
A systematic review and metaanalysis revealed that iloprost alone or iloprost plus recombinant tissue plasminogen activator (rtPA) may decrease amputation rate in case of severe frostbite in comparison to buflomedil alone with no major adverse events reported from iloprost or iloprost plus rtPA in the included studies.[31]
Various types of surgery might be indicated in frostbite injury, depending on the type and extent of damage.Debridement or amputation ofnecrotic tissue is usually delayed unless there isgangrene or systemic infection (sepsis).[7] This has led to the adage "Frozen in January, amputate in July".[32] If symptoms of compartment syndrome develop,fasciotomy can be done to attempt to preserve blood flow.[7]
Tissue loss andautoamputation are potential consequences of frostbite. Permanent nerve damage including loss of feeling can occur. It can take several weeks to know what parts of the tissue will survive.[16] Time of exposure to cold is more predictive of lasting injury than temperature the individual was exposed to. The classification system of grades, based on the tissue response to initial rewarming and other factors is designed to predict degree of longterm recovery.[7]
Grade 1: if there is no initial lesion on the area, no amputation or lasting effects are expected
Grade 2: if there is a lesion on the distal body part, tissue and fingernails can be destroyed
Grade 3: if there is a lesion on the intermediate or near body part, auto-amputation and loss of function can occur
Grade 4: if there is a lesion very near the body (such as the carpals of the hand), the limb can be lost. Sepsis and/or other systemic problems are expected.[7]
A number of long term sequelae can occur after frostbite. These include transient or permanent changes in sensation,paresthesia, increased sweating, cancers, and bone destruction/arthritis in the area affected.[33]
There is a lack of comprehensive statistics about theepidemiology of frostbite. In the United States, frostbite is more common in northern states. In Finland, annualincidence was 2.5 per 100,000 among civilians, compared with 3.2 per 100,000 in Montreal. Research suggests that men aged 30–49 are at highest risk, possibly because of occupational or recreational exposures to cold.[34]
Frostbite has been described in military history for millennia. The Greeks encountered and discussed the problem of frostbite as early as 400 BC.[16] Researchers have found evidence of frostbite in humans dating back 5,000 years, in an Andean mummy. Napoleon's Army was the first documented instance of mass cold injury in the early 1800s.[7] According to Zafren, nearly 1 million combatants fell victim to frostbite in the First and Second World Wars and the Korean War.[16]
Harold Bride, the junior wireless operator ofRMS Titanic, who suffered severe frostbite on his feet as he and other survivors stood for over an hour on the back of a capsized lifeboat knee-deep in freezing water—Bride had to be carried off from the rescue vesselRMS Carpathia after it arrived in New York
Scottish mountaineerJamie Andrew, who in 1999 had all four limbs amputated as a result of sepsis from frostbite sustained after becoming trapped for four nights whilst climbingLes Droites in theMont Blanc massif[38]
Medicalsympathectomy using intravenousreserpine has also been attempted with limited success.[33] Studies have suggested that administration oftissue plasminogen activator (tPa) either intravenously or intra-arterially may decrease the likelihood of eventual need for amputation.[45]
^abMarx, John (2010).Rosen's emergency medicine: concepts and clinical practice (7th ed.). Philadelphia, PA: Mosby/Elsevier. p. 1866.ISBN978-0-323-05472-0.
^Finderle Z, Cankar K (April 2002). "Delayed treatment of frostbite injury with hyperbaric oxygen therapy: a case report".Aviat Space Environ Med.73 (4):392–4.PMID11952063.
^Bruen, KJ; Ballard JR; Morris SE; Cochran A; Edelman LS; Saffle JR (2007). "Reduction of the incidence of amputation in frostbite injury with thrombolytic therapy".Archives of Surgery.142 (6):546–51.doi:10.1001/archsurg.142.6.546.PMID17576891.
