Wilderness Medicine
Frostbite
Background
- Definition(s)
- Damage to tissues exposed to temperature below the freezing point, < 32°F [0°C]
- Synopsis
- Cooling damage is worse if
- Cooling is slow
- Prolonged exposure
- Slow re-warming or partial re-warming and re-freezing
Pathophysiology
- Mechanism
- Freezing of tissue causing cellular injury or death resulting from prolonged exposure of flesh to < 32°F [< 0°C]
- Four overlapping pathologic phases
- Prefreeze
- Freeze-thaw
- Vascular Stasis
- Late Ischemia
- Ice crystals form in superficial or deep tissue causing protein derangements, electrolytes shifts resulting in cellular lysis and death.
- Subsequent thawing process results in reperfusion injury and inflammatory response
- Late ischemic process results in the release of oxygen free radicals, prostaglandin A2, proteolytic enzymes
- Commonly involves exposed tissues, hands, feet, ears, nose, cheeks; penis, scrotum in joggers
- Etiology/Risk Factors
- Ambient temperature < 28°F [> -2°C]
- High winds or altitude
- Use of tobacco, ethanol, and other drugs
- Poor nutritional status
- Contact with heat conductive materials (i.e. water or metal)
- Overexertion causing fatigue and sweat
- Prior frostbite injury
- Lack of adequate shelter or homelessness
- Raynaud's Phenomena
- Diabetes
- Peripheral neuropathies
- Alcohol intoxication
- Smoking
- Dehydration
- Tight clothing or rings/jewelry that restrict circulation
- Additional causes
- Contact with chemicals that induce low temperatures (i.e. dry ice, liquid nitrogen, liquid hydrogen)
- Epidemiology
- Incidence/Prevalence
- No standardized reporting: Incidence is unknown
- Seen predominantly in northern states and through the Midwest during winter as well as countries in the extremes of latitude.
- Outdoor workers /recreational activities (skiing, snowboarding, hunting, fishing)
- Mortality/Morbidity
- Mortality is rare, but morbidity is high
Diagnostics
- History/Symptoms
- Cold, hard, and/or firm tissue
- Difficulty walking or using extremity
- Numbness, burning or stinging of tissue
- Painful throbbing, burning sensations during re-warming
- Sometimes described as electric-current sensation
- Gather information of temperature, wind chill, and length of exposure if possible
- Physical Exam/Signs
- General appearance, vitals
- Discoloration, blue skin color, tenderness on exam, edema (View image)
- Frostbite of Toes (after about 2 weeks) (View image)
- HEENT
- Nose, ears, lips may be affected or discolored
- Musculoskeletal/Nervous System
- Paresthesia or anesthesia depending on degree of frostbite
- Skin/Extremities
- Skin necrosis or gangrenous changes may be seen
- Edema as well depending on degree of frostbite
- Labs/Tests
- No immediately useful lab tests or imaging
- Useful later in process for infection, sepsis, acidosis
- CBC +Diff
- Electrolytes
- CK
- Imaging
- Bone scans, MRI, angiography may be helpful to assess injury
- Have limitations
- Should not be used as definitive evidence of tissue death
- Tc-99 scintigraphy
- At 48 hours may be very sensitive/specific for ultimate extent of tissue injury
- Radiographic follow-up for 2 years evaluating for possible growth plate injuries, other bone lesions
- < 18 year old with partial thickness or greater injury need
- Other Tests/Criteria
- ECG
- May show dysrhythmias if associated with hypothermia or with other medical conditions
- Grading (field versus post-imaging)
- Field classification
- Superficial: no or minimal tissue loss expected
- Deep: tissue loss is anticipated due to extent of injury
- Superficial (1st degree)
- White patch of skin (waxy appearance)
- Diminished sensation diminished
- Rapid returns to normal
- Minor edema
- Partial thickness (2nd degree)
- Pale, cold but supple underlying tissue
- Clear fluid-filled vesicles appearing 12-24 hours after exposure
- Substantial edema
- Full thickness (3rd and 4th degree)
- Hard, non-pliable skin, severe pain with thawing
- Gangrene
- Bloody blisters apparent (3rd degree)
- Substantial edema
- Deep structures (muscle, tendon, bone) affected (4th degree)
- Deep red or cyanotic and mottled
- May progress to dry, black, mummified, profound necrosis
- Minimal edema
- May also consider the Hennepin Score, or Cauchy classification in predicting the amputation risk and need for expedient transfer out of a field setting
- Differential Diagnosis
Treatment
- Initial/Prep/Goals
- Do not re-warm if any chance of re-freezing (field re-warming)
- Initial evaluation for life-threatening injuries and trauma
- Remove wet clothing, give warm, dry blankets
- Assess for hypothermia
- Re-warm area, avoid trauma to area
- Thaw extremity if definitive care is greater than 2 hours away
- Thawing should utilize warm water bath as rapid rewarming has showed superior outcomes to slow rewarming
- Avoid massaging/rubbing tissue
- Cradle/elevate/splint extremity; keep on sterile linen
- Medical/Pharmaceutical
- Superficial, Partial thickness and deeper frostbite
- Thrombolytic Therapy
- Should only be performed in a location familiar with the medications and with the medications and with the ability to monitor
- Best results occur if administered within 12hrs of rewarming
- Aurlumyn (iloprost) injection
- FDA approved to treat severe frostbite in adults
- To reduce risk of finger or toe amputation
- Ibuprofen: 400 mg PO, or
- Aspirin: 325 mg PO prior to re-warming
- Goals
- Improve tissue salvage
- Protect from re-freezing
- May treat at home with rapid re-warming, anti-inflammatories
- Field procedures
- Thawing in field can render ambulatory patient non-ambulatory
- Due to pain and swelling
- Balance against time required for evacuation
- Longer extremity frozen results in greater injury
- Rapid Re-warming
- Put affected area in 104-108°F [40-42°C] water for 20-30 min
- Elevate extremity
- Separate damaged digits with dry gauze
- Apply bulky dressings
- Apply aloe vera or antibiotic ointment gently to all injured skin after thawing
- Pharmaceuticals
- Tetanus prophylaxis (high risk injury)
- Td and TIG if immunization status unclear
- Antibiotic therapy not indicated unless signs of infection
- IVF to optimize volume status
- Liberal use of pain medication and/or nerve blocks (usually needed for 7-10 days)
- Treatment of blisters is controversial
- Debride clear blisters and apply topical aloe vera
- Minimizes thromboxane-mediated tissue injury
- Leave hemorrhagic blisters alone (reduces infection risk)
- Whirlpool therapy BID with disinfectant treated water at 104°F [40°C] followed by range of motion exercises to prevent contractures
- A demanding physical therapist should be involved as early as possible
- 4-6 week or longer waiting period necessary to determine severity of injury
- Hyperbaric oxygen
- Controversial
- May speed and improve demarcation of dead and living tissue
- Oral peripheral vasodilators may help
- Controversial
- May increase pain
- Surgical/Procedural
- Surgical Debridement
- Do not consider for at least 4-6 weeks; up to three months to allow clear demarcation of necrotic tissue
- Should have a 2 mm line of liquefaction separating viable and non-viable tissue, with debridement to that line
- Allow for auto-amputation
- Does not remove living tissue
- Leaves good vascular bed for grafting
- Prevents phantom limb and retraction sequelae
- Grafts are often needed, but grafting too early leads to failure
- In severe cases, IV or intra-arterial tPA within 24 hours of injury to decrease microvascular thrombosis, salvage at-risk tissue and decrease risk of amputation
- Fasciotomy if compartment syndrome develops
- Complications
- Refreezing if thawed in the field
- Wound infections
- Intermittent pain and numbness
- Ulceration
- Hyperhidrosis/anhidrosis
- Vasomotor problems
- Osteoporosis
- Muscle atrophy
- Phantom limb pain post-amputation
- Prevention
- Minimize direct skin exposure
- Avoid tight boots or multiple sock layers in large boots
- Keep head, neck, face covered
- Mittens instead of gloves
- Stay hydrated
- Adequate caloric intake
- Avoid direct skin-metal or skin-fluid contact
- Remove jewelry and tight fitting clothes
Disposition
- Admission Criteria
- Typically admission, as degree of frostbite is difficult to determine on ED presentation
- Consults
- Medicine consult
- Surgery if gangrenous or necrotic tissue is present on presentation
- No indication for early surgical consult for amputation, only if escharotomy or fasciotomy required emergently
- Discharge/Follow-up instructions
- Only for patients with superficial frostbite and good social support and follow up
- May take 1-3 months for necrotic tissue to fully demarcate
- Risk factors contributing to frostbite, methods to avoid and treat it
- Prognosis
- 1°: full recovery
- 2°: soft tissue amputation
- 3°: bone amputation
- 4°: large amputation with systemic effects
- Follow-up 24-48 hours
- Return if worsening or new symptoms
References
- CDC. Hypothermia and Frostbite. Available at: https://www.cdc.gov/disasters/winter/staysafe/hypothermia.html. [Accessed August 2020]
- Dolbec KW, Higgins GL, Riedesel EL. Two patients with frostbite. Ann Emerg Med. 2013;62(2):194-200
- Mulgrew S, Khoo A, Oxenham T, James N. Cold finger: urban frostbite in the UK. BMJ Case Rep. 2013;2013. pii: bcr1120115167
- Ohki M, Ishikawa J, Kikuchi S. Oral frostbite due to dry ice. Ann Otol Rhinol Laryngol. 2012;121(10):675-677
- Russell KW, Imray CH, McIntosh SE, et al. Kite skier's toe: an unusual case of frostbite. Wilderness Environ Med. 2013;24(2):136-140
- Ikaheiumo TM, Junila J, Hiroven J, Hassi J. Frostbite and Other Localized Cold Injuries. In: Tintinalli JE, Kellen GD, Staphczynski JS, et al; (eds). Tintinalli's Emergency Medicine, 7th ed. New York, NY:McGraw-Hill Medical, 2011;Chapter 202
- Sahin C, Aysal BK, Karagoz H, Eren F, Ulkur E. A reason to be careful about frostbite injury: carbon dioxide fire extinguisher failure. Burns. 2013;39(4):e39-40
- Sakiyama M, Kawakubo Y. Preventable frostbite due to cold pack. Int Wound J. Jun 2015;12(3):366
- Vlachodimitropoulou E, Costello J. Frostbite from frosting. Emerg Med J. 2014;31(5):389
- Yanagisawa H. [Hypothermia, chilblain and frostbite]. Nihon Rinsho. 2013;71(6):1074-1078
- Zafren K. Frostbite: prevention and initial management. High Alt Med Biol. 2013;14(1):9-12
- McIntosh, Scott E., et al. “Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Frostbite: 2019 Update.” Wilderness & Environmental Medicine, vol. 30, no. 4, 2019, doi:10.1016/j.wem.2019.05.002.
Contributor(s)
- Chidester, Benjamin, MD
- Sindhwani, Maughan K., MD
- Laroy, Michael, DO
- Portouw, Steven, MD, FAAEM, FAWM
Updated/Reviewed: June 2021