Frostbite

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Background

  • Results from the freezing of tissue
  • It is a disease of morbidity, not mortality
  • Risk correlated with temperature and wind speed
    • Risk is <5% when ambient temperature (includes wind chill) is > –15C (5F)
    • Most often occurs at ambient temperature < –20C (–4F)
  • Can develop within 2-3sec when metal surfaces that are at or below –15C (5F) are touched
  • Most commonly affects distal part of extremities, face, nose, and ears
  • High-risk groups: outdoor workers, elderly, homeless, drug or alcohol abusers, psychiatric disease

Pathophysiology

  • Freezing alone is usually not sufficient to cause tissue death
    • Thawing contributes markedly to the degree of injury
    • Endothelial damage, beginning at the point of thaw, is the critical event in frostbite
      • Resulting damage results in swelling, platelet aggregation, vessel thrombosis

Zones of Injury

  1. Zone of Coagulation
    • Most severe and usually most distal
    • Damage is irreversible
  2. Zone of Hyperemia
    • Least severe and usually most proximal
    • Generally recovers with out treatment in <10d
  3. Zone of Stasis
    • Middle zone characterized by severe, but possibly reversible, cell damage
    • It is this zone for which treatment may have benefit

Clinical Features

Classification

  • Visual determination of tissue viability is difficult in first few weeks
  • Classify early injuries as superficial or deep
  • First degree (frostnip)
    • Partial-skin freezing
    • Stinging and burning, followed by throbbing
    • Numbness, erythema, swelling, dysesthesia, desquamation (days later)
    • Minimal pain with rewarming
    • Prognosis excellent
  • Second degree
    • Full-thickness skin freezing
    • Numbness followed by aching and throbbing
    • Substantial edema over 4-6 hours
    • Skin blisters form within 6-24 hours
      • Desquamate and form hard black eschars over several days
    • Mild to Moderate pain with rewarming
    • Prognosis is good
  • Third degree
    • Tissue loss involving entire thickness of skin
    • Extremity feels like a "block of wood" followed by burning, throbbing, shooting pains
    • Hemorrhagic blisters form and are associated with skin necrosis and blue-gray discoloration
    • Severe pain with rewarming
    • Prognosis is often poor
  • Fourth degree
    • Extension into subcutaneous tissues, muscle, bone, and tendon; little edema
    • Deep, aching joint pain
    • Skin is mottled with nonblanching cyanosis and formation of deep, dry, black eschar
    • Painless during rewarming
    • Prognosis is extremely poor

Differential Diagnosis

Cold injuries

Evaluation

  • Usually clinical

Management

  • Thawing
    • Do NOT attempt until the risk of refreezing is eliminated
      • Refreezing will cause even more severe damage
    • Rapid rewarming is the core of therapy and should be initiated as soon as possible
      • Extremities
        • Place in water with temperature of 40-42C (104-107.6)
        • Approximately 20-30min, until extremity is pliable and erythematous
        • OR consider 38-40°C in whirlpool bath with antibacterial soap[1]
      • Face
        • Apply moistened compresses soaked in warm water
  • Analgesia
    • Rewarming is very painful
    • Provide parenteral opioids
  • Local wound care
    • Apply topical aloe vera cream q6hr (interrupts arachidonic acid cascade)
    • Affected digits should be separated with cotton and wrapped with sterile, dry gauze
    • Elevate involved extremities
    • Blister removal is controversial
      • Consider drainage of nonhemorrhagic bullae that interfere with movement
      • Never debride hemorrhagic bullae
  • Systemic care
    • Ibuprofen may be helpful in interrupting arachidonic cascade
    • Heparin and hyperbaric oxygen of little value
    • IV tPA reduces digit amputation rate
  • Tetanus
    • Reported complication of frostbite; provide prophylaxis
  • Antibiotics
    • Controversial
    • Penicillin G 500,000 units IV Q6 hours for 48-72 hours
    • Topical bacitracin may be as good or better than IV penicillin
    • Silver sulfadiazine cream not consistently beneficial
      • May interact with aloe vera cream
  • Surgery
    • May be required if wet gangrene or infection occurs
    • Usually not performed until full demarcation occurs (3-4wk)

Disposition

  • Patients with superficial local frostbite may be discharged home if social circumstances allow

Complications

  • Up to 65% of patients with frostbite experience sequelae from their injuries
    • Hypersensitivity to cold, pain, ongoing numbness
    • Arthritis, bone deformities, scars, and skin and nail dystrophia

See Also

Video

References

  1. Crawford-Mechem C et al. Frostbite Treatment & Management. Aug 25, 2015. http://emedicine.medscape.com/article/926249-treatment#showall