Wilderness Medicine

Frostbite

Background

1. Definition(s)
   • Damage to tissues exposed to temperature below the freezing point, < 32°F [0°C]
2. Synopsis
   • Cooling damage is worse if
     • Cooling is slow
     • Prolonged exposure
     • Slow re-warming or partial re-warming and re-freezing

Pathophysiology

1. 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
2. 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)
3. 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

1. 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
2. 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
3. Labs/Tests
   • No immediately useful lab tests or imaging
   • Useful later in process for infection, sepsis, acidosis
   • CBC +Diff
   • Electrolytes
   • CK
4. 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
5. 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
6. Differential Diagnosis
   • Hypothermia
   • Trench foot
   • Pernio
   • Chilblain
   • Diabetic peripheral vascular disease

Treatment

1. 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
2. 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)
       • Morphine
       • Peripheral nerve blocks
   • 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
3. 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
4. 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
5. 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

1. Admission Criteria
   • Typically admission, as degree of frostbite is difficult to determine on ED presentation
2. 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
3. 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

1. CDC. Hypothermia and Frostbite. Available at: https://www.cdc.gov/disasters/winter/staysafe/hypothermia.html. [Accessed August 2020]
2. Dolbec KW, Higgins GL, Riedesel EL. Two patients with frostbite. Ann Emerg Med. 2013;62(2):194-200
3. Mulgrew S, Khoo A, Oxenham T, James N. Cold finger: urban frostbite in the UK. BMJ Case Rep. 2013;2013. pii: bcr1120115167
4. Ohki M, Ishikawa J, Kikuchi S. Oral frostbite due to dry ice. Ann Otol Rhinol Laryngol. 2012;121(10):675-677
5. 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
6. 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
7. 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
8. Sakiyama M, Kawakubo Y. Preventable frostbite due to cold pack. Int Wound J. Jun 2015;12(3):366
9. Vlachodimitropoulou E, Costello J. Frostbite from frosting. Emerg Med J. 2014;31(5):389
10. Yanagisawa H. [Hypothermia, chilblain and frostbite]. Nihon Rinsho. 2013;71(6):1074-1078
11. Zafren K. Frostbite: prevention and initial management. High Alt Med Biol. 2013;14(1):9-12
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)

1. Chidester, Benjamin, MD
2. Sindhwani, Maughan K., MD
3. Laroy, Michael, DO
4. Portouw, Steven, MD, FAAEM, FAWM

Updated/Reviewed: June 2021