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
[Outline]
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
[Outline]
The diagnosis of frostbite injury is primarily based on physical findings. Laboratory investigations provide limited value in initial assessment of injury.
Blood test findings
Chemistries
Renal function, electrolytes, glucose level, and creatine kinase may be indicated in the evaluation of potential rhabdomyolysis in cases with muscular injury or immobilization.
Other laboratory test findings
- Bacterial culture may be indicated if wound infection is suspected
- Blood culture may be indicated in cases of suspected sepsis or bacteremia
- Other selected testing may be indicated depending upon the suspected etiology of the cold exposure (e.g. in cases of ingestion/intoxication, trauma, septicemia, etc)
- Urine dip test with hemoglobin positive with microscopic showing no significant RBC's is consistent with myoglobinuria which can be indicative of rhabdomyolysis
Radiographic findings
- Technetium-99m scintigraphy (Tc-99)
- This test is a standard early diagnostic tool which can effectively assess the viability of injured tissue. It is sometimes used to support early debridement and prediction of outcomes
- A study demonstrated that Tc-99 scintigraphy can precisely indicate the level of amputation in >80% of patients
- Magnetic resonance angiography (MRA)
- MRA is another effective diagnostic technique that permits direct visualization of obstructed blood vessels and adjoining tissues, and helps distinctly demarcate ischemic tissues
- Other imaging techniques
- Other modalities such as plain radiography, angiography, magnetic resonance imaging (MRI), laser Doppler imaging, infrared thermography, and digital plethysmography may be used as adjuncts to physical examination; however, they are not known to accurately predict the severity and outcomes of frostbite
[Outline]
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]
Immunoglobulins- Tetanus immune globulin [IM]
VasodilatorsThrombolytic agentsDietary 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
[Outline]
