Version July 2025
INTRODUCTION —
Frostbite results from the freezing of tissue. It is a disease of morbidity, not mortality. It is most frequently encountered in mountaineers and other cold weather enthusiasts, soldiers, and individuals who work in the cold, are experiencing homelessness, or are stranded outdoors in the winter [1-5]. Among patients with severe frostbite, timely diagnosis and treatment are essential to maximize tissue salvage.
This topic review will discuss the classification, presentation, diagnosis, and management of frostbite. An algorithm summarizing evaluation and management is provided (algorithm 1). Severe hypothermia, high altitude illness, and other related illnesses are discussed separately.
●(See "Accidental hypothermia in adults: Clinical manifestations and evaluation" and "Accidental hypothermia in adults: Management".)
●(See "Nonfreezing cold water (trench foot) and warm water immersion injuries".)
●(See "Pernio (chilblains)".)
●(See "High-altitude illness: Physiology, risk factors, and general prevention" and "Acute mountain sickness and high-altitude cerebral edema" and "High-altitude pulmonary edema" and "High-altitude disease: Unique pediatric considerations".)
DEFINITIONS
●Frostbite – A localized cold-induced injury caused by freezing of tissue.
●Frostnip – Cold-induced, severe vasoconstriction of the skin with frost (ice crystals) on the surface of the skin. There is no ice in the tissue. Frostnip resolves after rewarming without permanent tissue damage.
●Warm ischemia time – The time from the start of thawing frostbitten tissue to reperfusion (ie, treatment with thrombolysis or vasodilator).
●Immersion foot ("trench foot") – A nonfreezing cold injury (NFCI) that results from prolonged exposure of the feet to a combination of dampness and cold and may also cause tissue loss and long-term sequelae. Immersion foot involves injury to the sympathetic nerves and vasculature of the feet. Feet and occasionally hands can be numb or extremely painful (picture 1). It was first described in 1914 during World War I trench warfare. Tight-fitting boots exacerbate the condition. Improved foot hygiene, including better boot design and frequent sock changes, resulted in a much lower prevalence among soldiers by 1917. Not just of historical significance, immersion foot was a major medical issue during the Falklands War of 1982 and still occurs, especially among individuals experiencing homelessness [6,7]. (See "Nonfreezing cold water (trench foot) and warm water immersion injuries".)
●Pernio ("chilblains") – A form of NFCI characterized by localized inflammatory lesions that can result from acute or repetitive exposure to cold. Lesions are red or purple, often nodular, and are often very painful or pruritic (picture 2). Pernio is most common in young females, but males and females of all ages may be affected [8]. Permanent damage from a single episode of pernio is uncommon, with symptoms and signs generally resolving within two to three weeks. (See "Pernio (chilblains)".)
PATHOPHYSIOLOGY —
The tissue destruction of frostbite is caused by immediate cold-induced cell death and the more gradual development of reperfusion-related localized inflammatory processes and tissue ischemia. Following exposure to subfreezing temperatures, ice crystals form extracellularly. If freezing is rapid, ice crystals may also form inside cells. Fluid and electrolyte fluxes cause lysis of cell membranes with subsequent cell death. An inflammatory process ensues, mediated by thromboxane A2, prostaglandin F2-alpha, bradykinins, and histamine. This leads to tissue ischemia and necrosis. The initial cellular damage and the subsequent inflammatory processes are made worse in the setting of thawing followed by refreezing of the affected area [3,9].
The complications of frostbite (eg, chronic pain, osteoarthritis) are caused primarily by peripheral neurovascular injury with associated abnormalities of sympathetic tone. Vasospasm, especially with re-exposure to cold, is common and may be life-long [10,11]. The severity of complications generally correlates with the severity of the original injury. The sequelae of nonfreezing cold injuries (NFCIs) may be similar but are often more debilitating than those produced by frostbite [12,13].
RISK FACTORS —
Frostbite develops within minutes to hours depending on circumstances and risk factors. Risk factors for developing frostbite and other cold-induced injuries include any condition that increases localized heat loss or decreases heat production. Examples include increased convective heat loss from exposure to wind or conductive heat loss from contact with metal, the ground, or water [14].
Exhaustion, dehydration, malnutrition, or comorbidities such as peripheral vascular disease, Raynaud phenomenon, diabetes, hypothyroidism, or mental illness may limit an individual's ability to respond to a cold stress. Alcohol use disorder predisposes to frostbite as a result of acute behavioral changes, increased heat loss from vasodilation, and chronic complications of alcohol consumption [15]. Other sedating or judgment-impairing drugs or medications pose a similar risk. Clearly, risk is greater at low ambient temperatures, when wind chill effects are increased, and at higher altitudes [4,15-19].
Additional risk factors for developing frostbite include smoking, previous cold injury, and exposure of the hands and arms to vibration, which can elicit a Raynaud-like phenomenon associated with white fingers in some individuals [20-22]. Data from the United States Armed Forces suggest that soldiers who are African American, female, or younger than 20 years of age are at increased risk of frostbite [23].
Use of clothing that provides inadequate insulation or coverage, or is damp, too tight, or permeable to wind, can predispose to frostbite, as can use of protective ointments, such as on the face. Studies from Norway in the 1990s showed that ointment use can enhance heat loss in some people and can provide users with a false sense of security, causing them to neglect standard safety measures [24-26]. Excessive sweating of the hands and feet increases an individual's risk of frostbite to those areas, illustrating the importance of clothing that can wick moisture away from the skin [27].
While generally considered a disease associated with exposure to cold air, frostbite has also been reported following direct exposure to freezing materials, such as the application of ice packs to reduce swelling from musculoskeletal injuries [28]. It is important to tell patients to interpose a cloth between the ice pack and their skin, and to limit treatment intervals to 20 minutes with at least a minute or two break between applications. Fingertip contact with a metal surface at a temp of -15°C (5°F) can lead to skin temperatures of 0°C (32°F) within several seconds [14].
Case reports describe severe facial, upper airway, and esophageal frostbite from recreational inhalation of halogenated hydrocarbons and nitrous oxide [29]. Contact with Freon, a fluorinated hydrocarbon used as a refrigerant, has been reported to cause deep frostbite of the hand [30-32], as can exposure to liquid nitrogen or dry ice. Frostbite of the foot has been described resulting from the discharge of a carbon dioxide fire extinguisher on a sprained ankle in an attempt to reduce edema [33]. Abdominal wall cryolipolysis can cause full thickness tissue loss, likely by frostbite combined with pressure necrosis [34,35].
Some researchers hypothesize that individual variation in cold-induced vasodilation (CIVD) corresponds to the risk of frostbite. The results of one observational study of the Royal Netherlands Navy during arctic training suggested that faster and greater CIVD may decrease risk [36], but subsequent studies have shown no correlation [37,38].
EPIDEMIOLOGY —
Because there is no formal reporting system for cases of frostbite, data on incidence and prevalence are mostly derived from selected subpopulations, generally consisting of individuals at greater than average risk [21,27,39]. In young Finnish males entering military service, the lifetime occurrence of mild and severe frostbite was 41 and 12 percent, respectively [21]. In a survey of mountaineers in Iran, there was a 37 percent annual incidence of frostbite [39]. In a study of 24,079 climbers on Denali, Alaska between 1992 and 2011, 831 needed medical assistance, of whom 171 were diagnosed with frostbite [40].
A study of the United State National Inpatient Sample from 2016 to 2018 (over 7 million records per year) estimated a general population incidence of frostbite requiring hospital admission of 0.83 per 100,000 persons [5].
CLINICAL MANIFESTATIONS
Acute manifestations — Areas commonly affected by frostbite include the hands (fingers), feet (toes), and face (ears, nose, cheeks, chin, fingers). Frostbite of the cornea has been reported in individuals who kept their eyes open against very strong winds [7,41].
Patients often complain of cold, numbness, and clumsiness of the affected area [42].
Before rewarming, the skin is insensate, white or grayish-yellow in color, and hard or waxy to touch (picture 3). Early signs of frostbite may be less conspicuous in patients with darker skin tones.
In superficial frostbite, erythema can develop immediately after thawing (picture 4). Within 24 hours, bullae containing clear or bloody fluid may develop near the tips of the fingers or toes (picture 5).
With deeper frostbite, cyanosis develops after thawing (picture 6 and picture 7 and picture 8 and picture 9). The extent of cyanosis predicts degree of injury. Early demarcation without early blister formation suggests deep injury (picture 10 and picture 11). (See 'Classification (grading) systems' below.)
Any patient with cyanosis proximal to the distal phalanx of any digit after rapid rewarming is at risk for necrosis of the affected tissue. Aggressive therapy (eg, thrombolysis in suitable candidates) may be needed to save tissue. (See 'Hospital-based initial management' below.)
Acute complications — Acute complications include gangrene and infection of affected areas. In cases with deep injury, the blisters are typically small, hemorrhagic, proximal, and usually form after 24 hours. Necrosis, characterized by a black eschar, usually becomes evident within a week (picture 12 and picture 13). Frostbite that extends to muscle and bone involves complete tissue necrosis, followed by mummification that occurs in 4 to 10 days.
Autoamputation may take several weeks to occur. Surgical amputation is necessary if deep infection develops before the autoamputation of nonviable tissue.
Rarely, acute compartment syndrome may develop and require emergency fasciotomy for decompression. (See "Acute compartment syndrome of the extremities".)
Long-term complications — Late and long-term or permanent sequelae include hypersensitivity to the cold, scarring, tissue atrophy, arthritis, decreased joint range of motion, bony abnormalities, and peripheral neuropathy, including hyper- or hypoesthesia of digits with decreased proprioception and chronic pain. The severity of complications generally correlates with the severity of the original injury.
Chronic pain — Throbbing pain that begins two to three days after rewarming may persist for weeks or months, even after nonviable tissue demarcates. Intermittent paresthesias beginning after one week are thought to be caused by ischemic neuritis and may last for months. Burning or electric shock sensations may also occur. Hyperhidrosis (excessive sweating) is common.
Frostbite osteoarthritis — Osteoarthritis caused by frostbite occurs most often in the distal extremities. There are numerous case reports of frostbite arthritis of hands in adults, usually not associated with loss of soft tissue. Early changes can include flexion contractures of the proximal interphalangeal joints that may improve over several months or become permanent, sometimes with arthrodesis [43]. Joint swelling may also be permanent and associated with osteo-degenerative changes and juxta-articular swelling of the proximal and distal interphalangeal joints (picture 14) [44-47]. In spite of deformities, good functional outcomes are common [43,44]. The thumbs are usually spared in frostbite arthritis, in contrast to typical osteoarthritis [48,49].
Frostbite arthritis of the feet causing flexion contractures of the toes has been reported [50]. Functional outcomes can be good [51] or debilitating [50]. Frostbite arthritis can occur in patients with underlying connective tissue disorders, such as scleroderma or Sjögren disease, producing a confusing clinical picture, especially if a history of frostbite is not elicited [52].
Frostbite arthritis has been known for centuries but was first described in modern times in a case series of 100 American soldiers who sustained frostbite injuries, primarily in their feet in the Korean War during 1950 to 1951 [51,53,54]. Transient, mostly mild osteoporosis developed in 58 soldiers. Subsequent changes to the bone consisting of sharply defined, punched out defects, usually near joints, were seen in 7 of 62 soldiers who were observed for at least eight months. There was no correlation between the severity of frostbite and the changes in the joints. Only one soldier had long-term clinical sequelae.
Epiphyseal destruction (children) — In children, epiphyseal destruction, bone abnormalities, and arthritis are potential sequelae, which are discussed further below. (See 'Children' below.)
DIAGNOSIS —
The diagnosis of frostbite is generally made on clinical grounds based on the context of the injury, signs, and symptoms. Frostbite should be suspected in a patient complaining of cold, numbness, or clumsiness of the affected area following exposure to cold. The diagnosis is confirmed by the presence of skin changes (eg, erythema, cyanosis). Classification of severity is based on examination findings following initial rewarming.
INITIAL MANAGEMENT —
Treatment can be divided into pre-hospital interventions, initial management, and definitive/subsequent care (algorithm 1). The approach described below is based on animal studies, observational data, clinical experience, and a relatively small number of clinical trials.
Prehospital care
●Get the patient to a warm environment as soon as possible. Whenever possible, cover, pad or splint the affected area to prevent further exposure, minimizing injury en route.
●Remove wet or restrictive clothing and jewelry.
●Avoid walking on frostbitten feet; this can increase tissue damage. If walking is necessary for evacuation, do not rewarm the feet before walking.
●Do not rewarm frostbitten tissue if there is a possibility of refreezing before reaching definitive care. This will result in worse tissue damage.
●If prehospital warming is attempted, options include placing the affected area in warm (not hot) water or warming it using body heat (eg, placing frostbitten fingers in the axillae).
●Do not rub frostbitten areas in an attempt to rewarm them; this can cause further tissue damage.
●Avoid the use of stoves or fires to rewarm frostbitten tissue. Frostbitten tissue is insensate, allowing the possibility of burns [9,41,55].
Hospital-based initial management — Once the patient has reached the hospital, initial care consists of treating life-threatening conditions, including associated trauma and hypothermia, rapid rewarming, wound care, efforts to enhance tissue viability, and prevention of complications [19,56-58]. In patients with severe frostbite, timely diagnosis and treatment are essential to maximize limb and digit salvage [59].
Address life-threatening conditions (eg, trauma, hypothermia) — Management of other, more serious conditions, such as severe hypothermia or internal hemorrhage from major trauma, takes priority over the treatment of frostbite, which is a disease of morbidity, not mortality. Management of hypothermia and trauma is discussed separately. (See "Accidental hypothermia in adults: Clinical manifestations and evaluation" and "Initial management of trauma in adults".)
Rewarming — Rewarming is most effectively accomplished by immersing the affected area in water heated to 37 to 39°C (98.6 to 102.2°F), ideally in a whirlpool so a steady temperature can be maintained [60]. An alternative to a whirlpool is a sous vide cooking device. The sous vide, inserted into a container of water, heats and circulates water at a set temperature [61]. Higher temperatures do not warm the injured area appreciably faster and cause the warming process to be much more painful. Dry heat is difficult to regulate and is not recommended. We use warm wet towels to rewarm body parts that cannot easily be immersed (eg, ears, nose), although no standard method exists.
Gentle active motion of the extremity while rewarming may help. Care should also be taken to avoid trauma to the injured area against the container walls during rewarming.
Rewarming of frostbitten tissue may be painful. Appropriate analgesia (eg, opioids) should be administered.
Thawing is usually complete when the tissue is red or purple and soft to the touch. Rewarming usually takes 15 to 30 minutes but may take up to one hour [62]. In mild frostbite, edema and blisters (picture 5) occur within hours of rewarming. In severe frostbite, there is little or no edema; proximal hemorrhagic blisters generally form after 24 hours.
Infection prophylaxis
●Tetanus is a reported complication of frostbite. Tetanus prophylaxis is recommended [63].
●Prophylactic antibiotics are controversial, and little evidence exists to guide decision-making. Post-thaw daily or twice daily warm whirlpool treatments are standard therapy to help to reduce bacterial colonization of injured tissue, but infection can develop nevertheless. We do not recommend routine use of prophylactic antibiotics. We suggest giving parenteral antibiotics at the earliest sign of infection. Staphylococci, streptococci, and pseudomonas species should be covered. Topical antibiotics can cause maceration and should be avoided; if given, antibiotics should be administered intravenously. Appropriate antibiotic selection is discussed separately. (See "Acute cellulitis and erysipelas in adults: Treatment", section on 'Acute cellulitis'.)
POST-REWARMING EVALUATION
Classification (grading) systems — After rewarming is complete, the extent of frostbite (ie, classification) must be determined to guide further management. A number of systems to classify frostbite have been developed based on initial clinical presentation, findings on scintigraphy with technetium-99m, and outcome [3,64-66].
We use the Cauchy grading system, a clinical prediction tool developed for frostbite of the hands and feet based on the level of cyanosis after rapid rewarming in warm water [12,65,67]. This approach does not rely on imaging to determine severity initially. The Cauchy grading system for frostbite is as follows (table 1):
●Grade 1 – Characterized by no cyanosis on the extremity (picture 4). This predicts no amputation and no sequelae.
●Grade 2 – Involves cyanosis isolated to the distal phalanx (picture 7). This predicts only soft tissue amputation and fingernail or toenail sequelae.
●Grade 3 – Characterized by intermediate and proximal phalangeal cyanosis (picture 8 and picture 11). This predicts bone amputation of the digit and functional sequelae.
●Grade 4 – Involves cyanosis over the carpal or tarsal bones (picture 9 and picture 13 and picture 10). This predicts bone amputation of the limb with functional sequelae [65].
The traditional classification system divided frostbite into four degrees of severity based upon the depth of tissue involvement in similar fashion to the classification of burns. This system gave clinicians a false sense of accuracy and caused many to treat frostbite injuries as if they were burns, with suboptimal results. Superficial frostbite generally corresponds to the traditionally described first and second-degree injury, while deep frostbite corresponds to third and fourth-degree injury. Depending upon rewarming methods and complications, such as infection or trauma, first and second-degree frostbite could unexpectedly become third or fourth degree. The traditional frostbite classification system into first through fourth degree is obsolete and should no longer be used. It is only of historical interest.
The Hennepin Score, patterned after total body surface scoring systems for thermal burns, is used for research purposes to describe the extent of tissue involved and quantify tissue salvage rates [68]. It is not a clinical tool.
Role of imaging studies in acute evaluation — In general, there is limited role for imaging in the acute evaluation and management of frostbite. Plain radiographs are not useful initially except to screen for trauma-related fractures.
Historically, patients with cyanosis proximal to the interphalangeal joints following rewarming were evaluated with computed tomography (CT) angiography [69-71] or technetium (Tc)-99m scintigraphy (bone scan) [72]; thrombolytic therapy was indicated if circulation was absent proximal to the interphalangeal joints. However, the use of imaging to determine thrombolytic candidates has been questioned because imaging can prolong the warm ischemia time [73]. Also, unlike technetium-99m scintigraphy, angiography does not visualize the microcirculation soon after injury, including in bone.
The role of imaging studies in subsequent management (ie, assessing tissue viability) is discussed below. (See 'Role of imaging studies in assessing tissue viability' below.)
SUBSEQUENT MANAGEMENT
Patient with severe injury (grade 3/4) — The degree of frostbite should be assessed using the extent of cyanosis immediately after rewarming (algorithm 1) [65]. (See 'Classification (grading) systems' above.)
Thrombolysis within 24 hours
●Indications, timing, and contraindications – In patients with severe frostbite (grade 3 or 4) frozen ≤24 hours and without history of freeze-thaw-refreeze presenting within 24 hours of thawing, we recommend treatment with intravenous (IV) tissue plasminogen activator (tPA; alteplase) plus subcutaneous low-molecular weight heparin (enoxaparin) or IV unfractionated heparin [69,72,74,75]. Contraindications to thrombolysis include, but are not limited to, recent stroke or persistent neurologic impairment, intracranial trauma, recent significant gastrointestinal bleeding, and recent surgery (table 2). The use of intra-arterial (IA) tPA with unfractionated heparin is also reasonable in facilities capable of administering IA tPA; the contraindications are slightly different (table 3). Patients appropriate for treatment with tPA are also appropriate for treatment with iloprost. (See 'Iloprost within 72 hours' below.)
Thrombolysis should be started as soon as possible, but no longer than 24 hours after thawing. Frostbite is associated with vascular thrombosis of affected tissue and these patients are at high risk for life-altering amputations. Rates of tissue salvage improve with decreasing time from rewarming to thrombolysis. For example, a study found that every hour delay in tPA was associated with an increased tissue salvage loss of 27 percent [59].
Thrombolysis is associated with a small but important risk of dangerous bleeding, such as intracranial hemorrhage. Clinicians must discuss the relative risks and benefits of thrombolytic treatment with the patient and obtain informed consent that the patient is willing to accept a small risk of potentially catastrophic bleeding in return for a greater likelihood of retaining functional digits or limbs. Before administering tPA, clinicians must carefully assess the patient's risk for significant bleeding complications. Do not give tPA to patients at significant risk for such complications, which are discussed in detail elsewhere. (See "Intravenous thrombolytic therapy for acute ischemic stroke: Therapeutic use", section on 'Complications' and "Acute ST-elevation myocardial infarction: Management of fibrinolysis", section on 'Absolute contraindications'.)
We recommend that tPA be given or withheld based only on physical examination after rewarming, with or without bedside doppler. According to the American Burn Association frostbite guidelines, thrombolytic therapy may be used for patients with cyanosis proximal to the distal phalanx (grade 3 or 4 frostbite) and demonstrated loss of perfusion at or proximal to the middle phalanx immediately after rewarming [76]. Even though assessing doppler signals of the digital arteries provides extra clinical information, this practice is not routinely necessary since it does not change acute management.
●Role of transfer/referral center – Whenever possible, treatment should be performed at or in consultation with a center experienced in the use of tPA for frostbite. Hospitals remote from centers experienced in the use of tPA for frostbite should establish protocols for administration of tPA in consultation with a referral center. For example, a study from Colorado found that administering tPA at the remote hospital prior to transfer (40 patients) was associated with fewer amputations compared with administering tPA at the referral center following transfer (32 patients) [77]. Photographs taken after rewarming were transmitted to the referral center for review before administration of tPA. No imaging studies were performed to determine the extent of frostbite damage, and extremity pulses were assessed by doppler when possible. Only one patient who received tPA before transfer had a significant bleeding event requiring transfusion.
●Administration and dosing – There are no standardized dosing regimens for tPA in the treatment of severe frostbite injury. Based on experience from Hennepin County Medical Center (Minneapolis, USA), treatment with IV alteplase and subcutaneous (SUBQ) enoxaparin is effective and more easily accomplished than treatment with intra-arterial (IA) tPA, but trials comparing IV and IA tPA for the treatment of severe frostbite have not been conducted. Reasonable approaches include the following:
•IV administration of alteplase – Administer a bolus dose of 0.15 mg/kg over 15 minutes, followed by a continuous IV infusion of 0.15 mg/kg per hour for six hours [59,76,78]. The maximum total dose is 100 mg. Infusion time may be less than six hours if maximum total dose is reached.
After the alteplase infusion is completed, adjunct treatment can be started with IV unfractionated heparin or SUBQ enoxaparin. The dose of IV unfractionated heparin is 500 to 1000 units/hour for six hours, or targeted to maintain the partial thromboplastin time (PTT) at twice the control value. Enoxaparin can be given at the therapeutic dose (1 mg/kg SUBQ twice daily for up to 14 days).
•IA administration of alteplase – Administer a bolus of 2 to 4 mg, followed by an infusion of 0.5 to 1 mg/hour via the femoral or brachial artery [69,70,79,80]. Perform repeat angiograms every 8 to 12 hours. (See "Intra-arterial thrombolytic therapy for the management of acute limb ischemia".)
Some centers administer an IA vasodilator, most commonly papaverine (150 mg), immediately before administering IA tPA [81,82]. We do not use papaverine, but there is little downside to its use.
If more than one extremity is affected, divide the total tPA dose between or among them. Treatment should be continued until perfusion is restored (as demonstrated by angiography or technetium-99m scanning) or a time limit of 72 hours is reached.
Adjunct treatment with unfractionated heparin can be given at 500 units/hour via the IA catheter.
●Supporting evidence – Evidence is largely observational but is robust [75,78,80,83-85]. A systematic review and meta-analysis (71 studies, 978 patients) found thrombolysis improved salvage rates [86]. Comparing thrombolysis with no thrombolysis, three studies using the Hennepin Score (tissue salvage rate) found a tissue salvage rate of 76 versus 49 percent; 10 studies using the digit salvage rate (one minus ratio of digits amputated to digits at risk) found 69 versus 48; and seven studies using the amputation rate found 30 versus 48 percent, respectively.
A meta-analysis (16 studies, 209 patients, 1109 digits treated with IV or IA tPA) found the digit salvage rate with IA or IV tPA was 76 and 62 percent, respectively [75]. Statistical analysis was not possible because of heterogeneity, but it is likely that there was no significant statistical or clinical difference in digit salvage rate between IV and IA tPA. While patient characteristics and study inclusion criteria varied, the authors of the review noted that thrombolytic therapy was less effective in patients with prolonged exposure (longer than 24 hours) or freeze-thaw-refreeze injuries. Another systematic review (17 studies, 216 patients treated with thrombolysis, total of 1844 limbs and digits) that included various thrombolytic agents found the weighted average of the limb salvage rate was 79 percent [83]. In historical controls, the digit salvage rate was 33 percent (95% CI 21-45 percent) for grade 3 and 2 percent (95% CI 0-5 percent) for grade 4 frostbite [65].
Iloprost within 72 hours — In patients with severe frostbite (grade 3 or 4) frozen ≤24 hours and without history of freeze-thaw-refreeze presenting within 72 hours of thawing, we recommend treatment with iloprost [87]. Iloprost, a prostacyclin analog, can be administered with or without thrombolysis. Iloprost should be used alone when tPA is contraindicated, as in frostbite seen more than 24 hours after thawing or in cases associated with trauma. Iloprost was approved by the US Food and Drug Administration for treatment of severe frostbite in February 2024.
Iloprost is given by continuous IV infusion for six hours/day for eight consecutive days at the maximum tolerable rate, up to 2 nanogram/kg per minute [87]. On the first three days, the infusion is started at a rate of 0.5 nanogram/kg per minute, and increased every 30 minutes by 0.5 nanogram/kg per minute, to a maximum of 2 nanogram/kg per minute (table 4). On days four through eight, the infusion is started at the highest tolerated rate from the previous day. If the patient develops non-tolerable adverse effects (eg, headache, hypotension), the dose is decreased by 0.5 nanogram/kg per minute until a tolerated rate is reached.
As with thrombolysis, we do not believe that imaging of perfusion is necessary before starting iloprost. Bedside doppler of digital arteries can be used if available but does not change management. When used without tPA, administration of iloprost does not require an intensive care setting.
In an open-label trial (47 patients, 252 digits with grade 3-4 frostbite), compared with buflomedil, iloprost with or without tPA was associated with lower amputation rates (2 versus 53 percent) [88]. There are additional case reports and series describing successful treatment with iloprost [85,89,90]. For example, in a retrospectives study (90 patients, 382 digits with grade 3-4 frostbite), compared with standard care, iloprost was associated with lower amputation rate for grade 3 (18 versus 44 percent) and grade 4 (46 versus 95 percent) frostbite [90]. Iloprost administration may be effective up to 72 hours, although supporting data are limited [91].
Since there can be overlap between grade 2 and 3 frostbite and iloprost is generally well tolerated, some experts will routinely administer iloprost to treat grade 2 frostbite [85,91]. When it is difficult to distinguish between grade 2 and 3 frostbite (ie, cyanosis close to the distal interphalangeal joint), we believe it is reasonable to offer iloprost. However, since grade 2 frostbite would not be expected to cause bony amputation, the decision should balance potentially limited soft tissue and nail loss against the inconvenience of an 8-day infusion, which will typically require hospitalization.
Iloprost can be used safely in prehospital settings if evacuation to a hospital is not feasible [66]. The dosing regimen is the same, but the infusion is stopped after a total of 50 mcg (one vial) has been given, regardless of the weight of the patient. The patient should be evacuated after the first dose. If this is not practical, the dose can be repeated daily for up to eight days, if feasible. A single dose is likely beneficial and should be given even if it is not possible to give subsequent doses.
All patients
Surgical consultation — Because frostbite may require long-term wound care, including hydrotherapy, repeated tissue debridement, escharotomy, fasciotomy, and possibly delayed amputation, we recommend early surgical consultation, preferably experienced in managing frostbite [55].
Wound care — Subsequent management includes application of a bulky dressing to the affected area, elevation to reduce edema, and daily hydrotherapy to improve range of motion. Splinting may be required to prevent contracture formation.
We recommend the following:
●Maintain aseptic technique during wound treatment.
●Apply nonadherent gauze as the first dressing layer.
●Use sterile fluff dressing.
●Insert pledgets (eg, sterile cotton) between digits to prevent tissue maceration during demarcation.
●Avoid occlusive dressings.
●Protect lower extremity wounds with a cradle and upper extremity wounds with sterile sheets.
●Whirlpool baths twice daily, keeping wounds open immediately following whirlpool treatment and allowing them to dry before applying any dressing. Whirlpool baths are intended to decrease the bacteria count, decreasing infection risk.
●Even though there is no clear consensus on management of frostbite-induced blisters, a reasonable approach is to drain, debride, and bandage large nonhemorrhagic bullae that interfere with movement, such as those over joints. Hemorrhagic bullae of comparable size and location are drained by aspiration but are not debrided. Other minor bullae should be left intact [9]. Some authors suggest that because of the high concentrations of inflammatory mediators in the blister fluid, all should be drained. Others take a more conservative approach. Hemorrhagic bullae reflect more significant damage to the microvasculature.
●Topical aloe, applied with dressing changes, and oral ibuprofen (adult dose 400 to 600 mg every 12 hours) or aspirin (adult dose 325 mg daily) may limit inflammation associated with frostbite by inhibiting thromboxane and prostaglandins, although supporting evidence is limited [92,93]. In the absence of contraindications, it is reasonable to use these treatments [94]. Analgesia or procedural sedation may be helpful to facilitate dressing changes.
Role of imaging studies in assessing tissue viability — Imaging studies are helpful in determining the existence of comorbidities, the extent of frostbite injury, and prognosis. Radiology studies can help to determine the extent of tissue involvement, response to therapy, and long-term tissue viability [95]. The most established study for patients with signs of or at risk for tissue necrosis from frostbite is technetium (Tc)-99m scintigraphy (bone scan). The appropriate role for each modality is described below:
●Technetium (Tc)-99m scintigraphy (bone scan) – This can be used to predict the long-term viability of affected tissue, with the goal of allowing early debridement or amputation of dead or dying areas while preserving viable tissue [59,66,68,96]. Scintigraphy on day 2 following injury may avoid the need for the traditional several-week delay in surgical intervention while awaiting demarcation between viable and nonviable zones. Scintigraphy has also been used to monitor response to a topical therapy protocol by demonstrating the effect of treatment on involved tissue microvasculature [64,97]. It can also help verify reperfusion following thrombolysis or iloprost.
●Plain radiographs – Late (weeks to months) radiographic findings in frostbite include bony destruction and, in children, damage to growth plates [9]. Frostbite arthritis often spares the thumbs, most likely because patients wrap them within clenched fists during the exposure [48].
●Fluorescence microangiography – This technique that has been used to monitor wound healing, has been used to monitor progression of perfusion in frostbite [98]. A study of 104 frostbite patients, of whom 26 were evaluated with both technetium-99m scanning and microangiography, found that amputation level correlated better with microangiography than with technetium-99m scanning [99].
●Single-photon emission computed tomography (SPECT) - Limited retrospective data suggests that a nuclear bone scan processed similarly to a computed tomography (CT) scan, combined with conventional CT (SPECT/CT), may be able to identify nonsalvageable tissue, allowing more accurate determination of the extent of tissue destruction and autoamputation than a conventional bone scan [81].
●Magnetic resonance (MR) – Some researchers believe that MR imaging (MRI) and MR angiography (MRA) may be superior to bone scans in establishing tissue viability. In case reports they have permitted visualization of occluded blood vessels and better demonstrated the line of demarcation between ischemic and nonischemic tissue. However, experience with MRI and MRA in frostbite is limited [9,100].
UNPROVEN THERAPIES —
Several potential but unproven treatments for frostbite have been reported.
●Hyperbaric oxygen – This has been proposed as an adjunctive therapy to improve revascularization and healing of injured tissue. Older studies showed no benefit, but subsequent case reports suggest a possible role and describe improvement in symptoms and the microcirculation of affected tissues [101-103]. A retrospective case series of 22 patients reported no definite improvement in the extent of amputations from hyperbaric oxygen therapy [104]. Further study of hyperbaric treatment is needed before it can be recommended. Hyperbaric oxygen therapy is discussed in greater detail separately. (See "Hyperbaric oxygen therapy".)
●Pentoxifylline – Sometimes used to treat claudication, pentoxifylline has been proposed as adjunctive therapy for frostbite because of its favorable effect on blood flow [105]. Although the benefit of pentoxifylline in claudication is limited, animal studies of frostbite have had positive results [106,107]. No controlled studies have been performed in humans. Further data are needed before pentoxifylline can be recommended. (See "Management of symptomatic peripheral artery disease: Claudication", section on 'Benefits not firmly established'.)
●Anticoagulation without thrombolysis – There is no evidence that intravenous unfractionated heparin alone improves outcomes in frostbite. We do not recommend it. For appropriately selected patients, unfractionated heparin, or enoxaparin, is given following thrombolytic therapy. (See 'Thrombolysis within 24 hours' above.)
●Microwave rewarming – A Russian study of low power microwave rewarming to restore perfusion of deep vessels in frostbitten extremities of 14 patients with grade 3-4 frostbite claimed to have prevented amputations in some patients and to have decreased expected amputation in others. The description of the methods is incomplete. Patients received 1 to 3 treatments "depending on the injury degree." It is unclear whether the first treatment was used for initial rewarming in some patients [108]. These results are very preliminary but seem potentially promising.
●Papaverine – Administering this vasodilator, followed by tissue plasminogen activator (tPA), has been associated with good patient outcomes in case reports [84]. However, a controlled trial of tPA with and without papaverine has yet to be performed.
●Nitroglycerin – This has also been used as a vasodilator to facilitate treatment with intra-arterial tPA [71].
●Sympathectomy – Evidence is lacking to recommend interruption of neural control intended to prevent vasoconstriction and limit tissue ischemia.
PREVENTION
All individuals — Prevention of frostbite includes minimizing predisposing factors, paying attention to weather forecasts, dressing appropriately for the weather, and having an emergency plan [15,16].
●Alcohol consumption and smoking should be avoided, as should exposure to water or metal surfaces.
●Adequate calorie intake and hydration should be maintained.
●Predicted high and low temperatures should be noted, as well as forecasted precipitation and wind chill index. In extreme cold temperatures and high winds, frostbite can develop in a matter of minutes [109].
●Suggested clothing includes a hat, face protection, eye protection under extreme conditions, mittens (as opposed to gloves), warm, water-resistant shoes, and several layers of loose-fitting clothes. The innermost layer should be a wicking material, such as polypropylene, that will draw moisture away from the skin. The next layer should be an insulating material such as fleece or wool. The outermost layer should provide protection against wind, rain, and snow. Wet clothing should be changed as soon as feasible [41].
●Small electric battery or chemical heat packs may be placed in gloves or shoes but should be used with caution and with a barrier to avoid burns through direct contact with the skin.
●The practice of applying emollients to exposed skin to prevent frostbite is widespread in many cold regions of the world. However, literature supporting this practice is lacking. There is evidence that this may give the user a false sense of security and increase the risk of frostbite. We do not suggest the use of emollients as a preventive measure [24-26].
●Individuals traveling in remote areas should, prior to departure, inform others of their anticipated route and carry adequate emergency supplies in case they become stranded.
●Persons frequently exposed to cold environments should be aware of common frostbite symptoms and signs and should withdraw to warm shelter if any of these symptoms occur.
Patients with previous frostbite — Cold exposure is contraindicated for six months after minor frostbite and for at least 12 months after any significant cold injury. Patients with frostbite remain at increased risk for developing frostbite from increased hypersensitivity to the cold [9,110]. Special precautions to protect previously injured tissue may need to be taken for several years if not indefinitely to prevent further damage.
SPECIAL POPULATIONS
Children — In children, epiphyseal destruction, bone abnormalities, and arthritis are potential sequelae after frostbite of the hands, and occasionally feet [12]. Frostbite need not be severe in order to be associated with damage to the digits. Most reported cases did not involve loss of tissue. Loss of fingernails with subsequent regrowth of normal nails often occurs during the several weeks following injury [111-114]. Multiple nails can be lost with regrowth over months to years [115]. Sometimes, there is sloughing of the epidermis without permanent tissue loss [111,116].
Bone and joint changes usually become evident several months after frostbite injury. Epiphyseal abnormalities, primarily of the distal and middle phalanges, include partial or complete destruction, fragmentation, and premature fusion (picture 15). Thumbs are seldom affected [115,117,118]. In the affected digits, the distal phalanges and sometimes the middle phalanges are shortened. Proximal phalanges and metacarpals are usually normal. Painful or painless joint swelling may begin 6 to 12 months after the injury [119]. Fingers commonly develop painless flexion deformities of the distal and proximal interphalangeal joints, often with radial deviation of the distal phalanges [114,119] and clinodactyly (curvature of the digits) [120]. Swan neck deformities can also occur [113,120]. Deep frostbite injuries with loss of tissue can cause severe sequelae with markedly limited range of motion of hands or feet [121].
Frostbite sustained at a young age can result in severe, progressive deformity with decreased range of motion and weakness in extension [112,115,117,118,121,122]. Chronic circulatory changes can include cold intolerance and vasomotor instability [120,123]. Deformities often worsen during growth spurts when affected bones fail to grow while unaffected bones develop normally [124]. When patients reach adulthood, radiographs show less specific changes of chronic arthritis with short phalanges [115]. Their hands often have limited dexterity, interfering with fine motor skills such as dressing and using a keyboard [115].
There are no specific data to guide treatment of frostbite in children. We recommend treating frostbite in children as in adults. There is no treatment proven to prevent permanent sequelae affecting bones and joints. In the largest published case series (13 patients seen 4 to 50 years after frostbite), no patient sought surgery to improve function or appearance caused by chronic disability [115].
SOCIETY GUIDELINE LINKS —
Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Management of environmental emergencies".)
INFORMATION FOR PATIENTS —
UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topic (see "Patient education: Frostbite (The Basics)")
SUMMARY AND RECOMMENDATIONS
●Risk factors – Risk factors for frostbite or nonfreezing cold injury (NFCI) include any condition that increases localized heat loss or decreases heat production. Examples include increased convective heat loss caused by exposure to wind or conductive heat loss from contact with metal or water. Exhaustion, dehydration, malnutrition, alcohol use disorder, or comorbidities such as peripheral vascular disease, diabetes, substance use, experiencing homelessness, or mental illness also increase risk. (See 'Risk factors' above.)
●Clinical manifestations – The areas most frequently affected by frostbite are the ears, nose, cheeks, chin, fingers, and toes. Patients often complain of cold, numbness, and clumsiness of the affected area. The skin may be insensate, white or grayish-yellow in color, and hard or waxy to touch. Bullae containing clear or hemorrhagic fluid may form within 24 hours after thawing. (See 'Clinical manifestations' above.)
Acute complications include gangrene and infection of the affected area. Post-thaw compartment syndrome rarely occurs but may require fasciotomy. Late and long-term or permanent sequelae include hypersensitivity to the cold, scarring, tissue atrophy, arthritis, bony abnormalities, decreased joint range of motion, and peripheral neuropathy, including hyper- or hypoesthesia of digits with decreased proprioception and chronic pain. The severity of complications generally correlates with the severity of the original injury. (See 'Acute complications' above and 'Long-term complications' above.)
●Initial care and rewarming – Initial care consists of addressing life-threatening conditions (eg, trauma, hypothermia), rapid rewarming, wound care, efforts to enhance tissue viability, and prevention of complications (algorithm 1). Rewarming is most effectively accomplished by immersing the affected area in a circulating water bath heated to 37 to 39°C (98.6-102.2°F) that feels warm but not hot to an unaffected hand. Rewarming may be painful, and appropriate analgesia should be administered. Thawing is usually complete when the tissue is red or purple and soft to the touch. (See 'Initial management' above.)
●Assess severity/classification – After rewarming is complete, the severity of frostbite using the extent of cyanosis must be determined to guide further management. Grades 3 or 4 (by intermediate and proximal phalangeal cyanosis) constitutes a severe injury. (See 'Classification (grading) systems' above.)
●Role of imaging – There is limited role for imaging in the acute evaluation and management of frostbite. Technetium-99m scintigraphy (bone scan) can be used to predict long-term viability of affected tissue and is performed on day 2 following injury. Bone scan should not be used to determine need for other acute therapies (ie, thrombolysis, iloprost). (See 'Role of imaging studies in acute evaluation' above and 'Role of imaging studies in assessing tissue viability' above.)
●Subsequent management
•All patients – Because frostbite may require long-term wound care, including hydrotherapy, repeated tissue debridement, escharotomy, fasciotomy, and possibly delayed amputation, we obtain early surgical consultation. Wound care includes application of a bulky dressing to the affected area, elevation to reduce edema, and daily hydrotherapy to improve range of motion. (See 'All patients' above.)
•Patients with severe injury (grade 3/4)
-Thrombolysis with anticoagulation – In patients with severe frostbite (grade 3 or 4), we recommend treatment with intravenous tissue plasminogen activator (tPA; alteplase) plus subcutaneous low-molecular weight heparin (enoxaparin) or intravenous (IV) unfractionated heparin if all of the following are met (Grade 1C): frozen ≤24 hours; no history of freeze-thaw-refreeze; within 24 hours of thawing. Contraindications to thrombolysis include, but are not limited to, recent stroke or persistent neurologic impairment, intracranial trauma, recent significant gastrointestinal bleeding, and recent surgery (table 2). Treatment with intra-arterial tPA and intra-arterial unfractionated heparin is also reasonable in hospitals that prefer this approach; the contraindications are slightly different (table 3). Frostbite is associated with vascular thrombosis of affected tissue and these patients are at high risk for life-altering amputations. Rates of tissue salvage improve with decreasing time from rewarming to thrombolysis. (See 'Thrombolysis within 24 hours' above.)
Whenever possible, treatment should be performed at or in consultation with a center experienced in the use of tPA for frostbite. Clinicians must discuss the relative risks and benefits of thrombolytic treatment with the patient and obtain informed consent that the patient is willing to accept a small risk of potentially catastrophic bleeding in return for a greater likelihood of retaining functional digits or limbs.
-Iloprost – In patients with severe frostbite (grade 3 or 4), we recommend treatment with iloprost if all of the following are met (Grade 1C): frozen ≤24 hours; no history of freeze-thaw-refreeze; within 72 hours of thawing. Iloprost, a prostacyclin analog, can be administered with or without thrombolysis. Iloprost is given by IV infusion for six hours/day for eight consecutive days, titrated to a tolerable rate (table 4). Iloprost has been associated with lower amputation rates. (See 'Iloprost within 72 hours' above.)
●Prevention – Strategies for prevention of frostbite includes minimizing predisposing factors, paying attention to weather forecasts, dressing appropriately for the weather, and having an emergency plan. Cold exposure is contraindicated for six months after minor frostbite and for at least 12 months after any significant cold injury. (See 'Prevention' above.)
ACKNOWLEDGMENT —
The UpToDate editorial staff acknowledges C Crawford Mechem, MD, FACEP, who contributed to earlier versions of this topic review.
