Frostbite

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 temp < –20C (–4F)
• Can develop w/in 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

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
  • Zone of Coagulation
    • Most severe and usually most distal
    • Damage is irreversible
  • Zone of Hyperemia
    • Least severe and usually most proximal
    • Generally recovers w/o treatment in <10d
  • 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

1. First degree (frostnip)
   1. Partial-skin freezing
   2. Stinging and burning, followed by throbbing
   3. Numbness, erythema, swelling, dysesthesia, desquamation (days later)
   4. Prognosis excellent
2. Second degree
   1. Full-thickness skin freezing
   2. Numbness followed by aching and throbbing
   3. Skin blisters form w/in 6-24hr
      1. Desquamate and form hard black eschars over several days
   4. Prognosis is good
3. Third degree
   1. Damage extends into subdermal plexus
   2. Extremity feels like a "block of wood" followed by burning, throbbing, shooting pains
   3. Hemorrhagic blisters form and are a/w skin necrosis and blue-gray discoloration
   4. Prognosis is often poor
   5. Tissue loss involving entire thickness of skin
4. Fourth degree
   1. Extension into subcutaneous tissues, muscle, bone, and tendon; little edema
   2. Deep, aching joint pain
   3. Skin is mottled w/ nonblanching cyanosis and formation of deep, dry, black eschar
   4. Prognosis is extremely poor

Treatment

1. Thawing
   1. Do NOT attempt until the risk of refreezing is eliminated
      1. Refreezing will cause even more severe damage
   2. Rapid rewarming is the core of therapy and should be initiated as soon as possible
      1. Extremities
         1. Place in water w/ temperature of 40-42C (104-107.6)
         2. Leave in for 20-30min, when the extremity should become pliable and erythematous
      2. Face
         1. Apply moistened compresses soaked in warm water
2. Analgesia
   1. Provide parenteral opiates
3. Local wound care
   1. Apply topical aloe vera cream q6hr (interrupts arachidonic acid cascade)
   2. Affected digits should be separated w/ cotton and wrapped w/ sterile, dry gauze
   3. Elevate involved extremities
   4. Blister removal is controversial
      1. Consider drainage of nonhemorrhagic bullae that interfere w/ movement
      2. Never debride hemorrhagic bullae
4. Systemic care
   1. Ibuprofen may be helpful in interrupting arachidonic cascade
   2. Prophylactic tx is controversial; Pen G 500K untis IV q6hr may be beneficial
   3. Intra-arterial tPA reduces digit amputation rate
5. Tetanus
   1. Reported complication of frostbite; provide prophylaxis
6. Surgery
   1. May be required if wet gangrene or infection occurs
   2. Usually not performed until full demarcation occurs (3-4wk)

Complications

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

Disposition

• Pts w/ superficial local frostbite may be discharged home if social circumstances allow

See Also

Cold Injuries (Non-Freezing)

Source

Tintinalli