Topic Editor: Grant E. Fraser, M.D., FRACGP, FACRRM, ASTEM

Review Date: 2/12/2013

Definition

Frostbite is a localized injury due to freezing of body tissues due to exposure to sufficiently cool temperatures for sufficient duration. Freezing of tissue results in crystallization within tissues which begins a pathway of destruction of cells, vasculature and tissue.

Description

• Frostbite is classified based on the depth of tissue freezing:
• 1st degree frostbite includes erythema, numbness, and a white or yellow plaque
• 2nd degree frostbite includes erythema and edema surrounding superficial vesicles or blisters which contain clear or milky fluid
• 3rd degree frostbite involves a deeper injury of the dermis with blisters that are usually purple and contain blood
• 4th degree frostbite involves structures deeper than the dermis such as muscles, bones, and nerves
• Frostbite typically progresses from distal to proximal body regions, and from superficial to deep tissue
• The severity of frostbite may range from marginal tissue damage to profound tissue necrosis that necessitates amputation
• Limbs (especially digits), cheeks, nose, ears, and penis are the most commonly affected regions
• Frostbite is frequently accompanied by other cold injuries such as systemic hypothermia
• Military activities, winter sports, alcohol abuse, and homelessness are the most common risk factors for frostbite

Epidemiology

Incidence/Prevalence

• The exact prevalence of frostbite is unclear due to lack of reporting. It occurs most commonly among those who partake in activities such as mountaineering, skiing, winter hunting and other outdoor activities in the severe cold
• US Army data from 1980–1990 indicate cold weather injuries accounted for 2143 hospitalizations of which 43.8% were frostbite
• According to a 2005 study, the annual incidence of frostbite among mountaineers was 366/1000 population
• A high incidence of frostbite was reported in 2010 among the civilian population of northern Europe due to an unusually cold winter

Age

• Frostbite occurs most commonly in adults aged 30–49 years; however, the elderly and the young are more susceptible to developing frostbite in a given environment
• The peak age range of 30-49 years relates to these individuals being more commonly involved in activities which place them at risk

Gender

• The incidence of frost bite is higher in males than females. This can be attributed to increased occupational exposure of males to cold environments

Race

• African-Americans have a higher risk of developing frostbite than Caucasians
• In one review of peripheral cold injuries in the Falkland Islands conflict, under similar dress and conditions, those of African origin had a 30 fold greater chance of injury, also with increased severity, whereas Pacific Islander origin increased risk by 2.6 times

Risk factors

• General
• Age extremes (elderly and young individuals)
• Alcohol consumption
• Constrictive clothing or jewelry
• Drug use (vasoconstrictors, sedatives, neuroleptics, beta blockers, illicit drugs)
• Exposure to moisture or high wind chill factor
• Handling of compressed gases (liquid oxygen, nitrogen, ammonia, etc)
• High altitude
• Homelessness
• Insufficient clothing and shelter
• Military activities in cold environments
• Prolonged exposure to cold
• Prolonged immobility
• Race (African or Pacific Island origin)
• Smoking
• Winter sporting activities
• Physiological
• Arthritis
• Atherosclerosis
• Cryoglobulinopathies
• Dehydration
• Diabetes
• Hyperhidrosis
• Hypothermia
• Hypovolemia
• Hypoxia
• Immobilizing trauma of head, spine, limbs
• Infection or sepsis
• Lack of acclimatization to a cold environment
• Malnutrition
• Mental illness
• Neuropathy
• Peripheral vascular disease
• Previous cold injury
• Reynaud's phenomenon
• Vasculitis

Etiology

• The most common cause of frostbite injury is prolonged exposure to a cold environment
• The severity of frostbite correlates with the temperature, length of exposure, and extent and depth of tissue freezing. Wind chill can result in a more rapid heat loss, which leads to more rapid freezing and deeper injury
• Pathophysiology
• Exposure to severe cold results in peripheral vasoconstriction as an adaptive mechanism to preserve central temperatures. This vasoconstriction markedly diminishes flow to the periphery allowing these tissues to rapidly cool, and in a sufficiently cold environment to freeze
• As a result of freezing, cells are destroyed due to marked changes in electrolyte concentrations with intracellular and extracellular crystallization of water within tissue
• Vascular freezing typically progresses from the microcirculation (capillaries) to veins and finally to arteries
• With freezing, blood vessel further constrict leading to decreased blood flow. Further changes then occur including vascular endothelial injury with significant risk of thrombosis, embolization, and activation of coagulation pathways with fibrin deposition
• Microthrombi formed due to endothelial damage obstruct capillaries and further contribute to tissue ischemia
• Rewarming leads to lysis of frozen cells with resulting tissue edema and further vascular endothelial damage
• Repeated cycles of freezing and thawing worsens thrombosis and ischemia exacerbating tissue loss
• Frozen tissue is compromised by a combination of vascular ischemia, local cellular damage and autonomic dysfunction. Tissue loss with gangrene or even mummification occurs in severe frostbite

History

• History regarding the timing and cause of frostbite should be determined
• It is important to investigate the probable temperature, wind chill, and duration of exposure
• Patient co-morbid medical conditions should be sought
• Seek history of any substance abuse which may have contributed
• A combination of history and physical examination are useful in assessing degree of injury and prognosis
• Tetanus immunization status (if not fully immunized will need immunoglobulin and immunization)

Physical findings on examination

Physical findings vary by intensity of the frostbite injury

• Superficial (mild) frostbite
• First degree
• Partial thickness of skin is frozen
• Reddish or hyperemic appearance of frozen tissue
• Mild edema
• Infrequent skin desquamation
• Absence of blisters
• Second degree
• Full thickness of skin is frozen
• Reddish appearance of frozen tissue
• Clear fluid-filled blisters
• Significant edema
• Deep (severe) frostbite
• Third degree
• Full thickness of skin and subcutaneous tissue are frozen
• Bluish-grey appearance of frozen tissue
• Hemorrhagic blisters
• Necrosis
• Significant edema
• Fourth degree
• Full thickness of skin, subcutaneous tissue, tendon, muscle and bone are frozen
• Minimal or no edema
• Intense necrosis
• Initially deep red or cyanotic appearance of frozen tissue
• Frozen tissue ultimately appears black and mummified

• Frostnip
• Pernio (chilblains)
• Thermal burns
• Trench foot (immersion syndrome)

General treatment items

• Primary management of frostbite can be divided into three stages: field care, hospital care, and post-thaw care
• Field care
• ABC's and treatment of hypothermia take precedence over care for frostbite
• The patient should be moved away from wind to a sheltered environment to prevent further injury
• Wet clothing, footwear, and gloves should be replaced with warm and dry ones
• Any kind of trauma or limb compression should be avoided
• The injured area(s) should not be rubbed or have direct heat applied
• The injury should be covered with a dry, sterile dressing without breaking the blisters
• Patients at high altitudes should be administered supplemental oxygen and fluids before descent
• Field rewarming should only occur if there is no risk of refreezing while in transit to hospital care
• Hospital care
• Once admitted, it is essential to promptly address a patient's systemic hypothermia and concomitant injuries, if any
• If hypothermia is present, the patient should be brought to a core temperature of 34°C before proceeding with specific care for frostbite
• Rewarming may be performed by immersion of the injured area in a whirlpool bath at 40-42 °C, containing a mild antibacterial such as chlorhexidine. Duration of rewarming is generally based upon clinical assessment, and may take up to 1 hour for deep injuries
• Rewarming should be continued until the affected tissue appears red/purple in color and flexibility is evident
• Patients should receive appropriate fluid resuscitation to treat dehydration and cold diuresis which may accompany hypothermia
• Reperfusion pain should be treated with standard narcotic analgesics, and rewarming should continue until clinical assessment indicates appropriate rewarming has occurred
• Tetanus immunization should be administered (if not immunized also provide tetanus immunoglobulin)
• Post-thaw care
• Clear or milky fluid-filled blisters should be debrided and continually covered using aloe vera dressing . If aspiration of hemorrhagic blisters is required due to restricted movement, it should be done aseptically leaving their roofs intact
• Meticulous wound care is extremely crucial. Extremities should be cleaned with whirlpool baths containing chlorhexidine and dressed twice daily
• Affected limbs must be elevated, splinted, and loosely bandaged to impede further edema and venous stasis
• Prophylactic antibiotics remain controversial, but are widely used for any significant wound in an attempt to decrease rate of infection in necrotic tissue
• The primary goal of hospital care is providing the patient with comfort, nourishment, hydration, and analgesia
• Surgical interventions
• Early fasciotomy/escharotomy following post-thaw care is indicated if compartment syndrome develops
• Early surgery is associated with an increased mortality, hence it is practical to withhold amputation for 6–12 weeks post injury until the level of demarcation is well-defined
• However, early amputation/debridement may be indicated in presence of severe systemic infection, sepsis, liquefaction, or wet gangrene
• Precise prediction of tissue and bone viability is possible using TC-99 scans and MRA
• Physiotherapy and other multidisciplinary rehabilitation approaches are essential to improve the functional outcomes of surgery
• Adjunctive therapies
• Thrombolysis
• Parenteral thrombolytic therapy may improve outcomes of severe frostbite by clearing the obstructing thromboses in the tissue microvasculature
• A small study demonstrated benefit of tissue plasminogen activator (t-PA) along such as alteplase (along with heparin) in significantly decreasing rates of amputation. This benefit was only demonstrated in cases receiving t-PA within 24 hours of the injury
• Vasodilators
• Iloprost, a prostacyclin analogue, has significant vasodilator and antiplatelet activity mimicing sympathectomy
• Pentoxifylline, a phosphodiesterase inhibitor, is also known to improve blood circulation in affected areas, reduce platelet hyperactivity and stabilize prostacyclin to TXA2 ratio
• Hyperbaric oxygen (HBO)
• HBO is known to improve the flexibility of erythrocytes, decrease development of edema, and has bacteriostatic and antioxidant properties
• However, the effectiveness of hyperbaric oxygen therapy (HBO) therapy in frostbite remains debatable and requires further study
• Sympathectomy
• Chemical (nerve block) or surgical sympathectomy is believed to limit tissue loss in frostbite patients. Studies have demonstrated that surgical sympathectomy may decrease the duration of pain and promote tissue demarcation. Similarly use of IV guanethidine has exhibited some success

Medications indicated with specific doses

Toxoids

• Tetanus toxoid adsorbed [IM]
• Adult Dosing
• Pediatric Dosing

• Tetanus immune globulin [IM]
• Adult Dosing
• Pediatric Dosing

• Pentoxifylline
• Adult Dosing
• Pediatric Dosing

• Alteplase [IV]
• Adult Dosing

Dietary or Activity restrictions

• As a preventive, alcohol consumption should be avoided as it increases the risk of developing frostbite
• Adequate fluid intake and consumption of energy-rich foods are essential in preventing dehydration and enabling heat production in the body

Disposition

Admission Criteria

• Presence of frostbite generally requires hospital admission

Discharge criteria

• Patients with minimal superficial injuries with an appropriate and safe destination and follow-up may occasionally be discharged

Monitoring

• Central body temperature of patients should be continuously measured using electronic probes (vascular, bladder, esophageal, or rectal)
• Monitoring for complications such as compartment syndrome and rhabdomyolysis should occur in selected cases
• Patients should be regularly monitored for progress of physical rehabilitation, infection, and other complications

Complionicats

• Altered biomechanics of limbs following amputation
• Arthralgia
• Causalgia (pain syndrome from damage to peripheral nerves)
• Chronic vasomotor pain refractory to analgesics
• Growth-plate damage
• Heterotrophic calcification
• Hyperhidrosis
• Increased sensitivity to cold
• Loss of nails on affected digits
• Muscle or other soft tissue loss
• Necrosis/gangrene
• Osteoarthritis
• Paraesthesias
• Renal failure
• Rhabdomyolysis
• Sensory loss
• Skin changes with poor skin integrity
• Tissue loss including amputations
• White fingers

Prevention

• It is essential to avoid wet clothing, and staying in the same position for a prolonged duration during exposure to extreme cold
• Use of protective, non-constrictive clothing and footwear can significantly reduce the occurrence of cold injuries such as frostbite. Synthetic fabrics which are lightweight, insulating, and quick-drying are preferable
• Clothing, footwear and gloves should be multilayered with water-repellent outer covers to improve conservation of body heat, and allow for stripping of layers during exertion
• Acclimatization to cold weather, adequate food and fluid intake, physical exercise, and avoiding smoking, alcohol consumption, and fatigue are also essential for prevention of frostbite
• Patients at risk of frostbite such as outdoor sportsmen should be educated about recognition and prevention of frostbite
• Use of chemical/electric hand and foot warmers and supplemental oxygen above 7500 meters is recommended during mountaineering expeditions

Prognosis

• Frostbite is predominantly a disorder of morbidity rather than mortality, except when accompanied by systemic hypothermia
• Indicators of favorable prognosis include
• Clear appearance of fluid inside blisters
• Early edema development with blisters extending to fingertips
• Normal skin color
• Preserved sensation
• Indicators of poor prognosis include
• Absence of edema
• Non-blanching cyanosis
• Proximal hemorrhagic vesicles
• Stiff skin
• Differentiating viable and non-viable tissue may require several weeks to months
• Refreezing injuries are associated with poor prognosis
• In case of amputation of fingers, toe-to-hand transfer may provide a beneficial option

Associated conditions

• Hypothermia

Synonyms

• Cryopathy

ICD-9-CM

• 991.0 Frostbite of face
• 991.1 Frostbite of hand
• 991.2 Frostbite of foot
• 991.3 Frostbite of other and unspecified sites

ICD-10-CM

• T33.01 Superficial frostbite of ear
• T33.02 Superficial frostbite of nose
• T33.09 Superficial frostbite of other part of head
• T33.1 Superficial frostbite of neck
• T33.2 Superficial frostbite of thorax
• T33.3 Superficial frostbite of abdominal wall, lower back and pelvis
• T33.4 Superficial frostbite of arm
• T33.5 Superficial frostbite of wrist, hand, and fingers
• T33.6 Superficial frostbite of hip and thigh
• T33.7 Superficial frostbite of knee and lower leg
• T33.8 Superficial frostbite of ankle, foot, and toe(s)
• T33.9 Superficial frostbite of other and unspecified sites

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