Frostbite

Background

Whid chill chart

• 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 > –15°C (5°F)
  • Most often occurs at ambient temperature < –20°C (–4°F)
• Wetness and humidity increase the risk (water has 25x thermal conductivity of air)
• Can develop within 2-3sec when metal surfaces that are at or below –15°C (5°F) 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, high-altitude or cold-weather athletes, military personnel
• "Hunter's response" - prolonged repeated exposure to cold is protective

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 Stasis
   • Middle zone characterized by severe, but possibly reversible, cell damage
   • It is this zone for which treatment may have benefit
3. Zone of Hyperemia
   • Least severe and usually most proximal
   • Generally recovers without treatment in <10d

Clinical Features

Classification

Visual determination of tissue viability is difficult in first few weeks; classify early injuries as superficial or deep

Degree	First (frostnip)	Second	Third	Fourth
Pathophys	Partial-skin freezing	Full-thickness skin freezing	Tissue loss involving entire thickness of skin	Extension into subcutaneous tissues, muscle, bone, and tendon; little edema
Symptoms	Stinging and burning, followed by throbbing	Numbness followed by aching and throbbing	Extremity feels like a "block of wood" followed by burning, throbbing, shooting pains	Deep, aching joint pain
Course	Numbness, erythema, swelling, dysesthesia, desquamation (days later)	Substantial edema over 4-6 hours; skin blisters form within 6-24 hours; Desquamate and form hard black eschars over several days	Hemorrhagic blisters form and are associated with skin necrosis and blue-gray discoloration	Skin is mottled with nonblanching cyanosis and formation of deep, dry, black eschar
Pain with rewarming	Minimal	Mild to moderate	Severe	None
Prognosis	Excellent	Good	Often poor	Extremely poor
Image

Differential Diagnosis

Cold injuries

• Generalized
  • Accidental hypothermia
  • Therapeutic hypothermia
• Freezing
  • Frostbite
• Non-freezing
  • Trench foot
  • Chilblains (Pernio)
  • Cold panniculitis
  • Cold urticaria
  • Polar thigh

Evaluation

Second degree frostbite progression.

• Usually clinical

Management

• If hypothermia present, must rewarm to a core temperature of at least 35°C before treating frostbite
• Remove all wet or constrictive clothing
• 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 37 to 39°C (98.6 to 102.2°F)
      • Approximately 20-30min, until extremity is pliable and erythematous
      • OR consider 38-40°C in whirlpool bath with antibacterial soap
    • 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
  • Compartment Syndrome is a known complication; maintain a high suspicion
• Systemic care
  • Ibuprofen may be helpful in interrupting arachidonic cascade
  • tPA or IV Iloprost (not available in US), followed by several days of heparin, reduces digit amputation rate for 3rd and 4th degree frostbite
  • Hyperbaric oxygen therapy is of theoretical benefit but no randomized trials have been performed
• 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
• Significant injuries will require ICU admission

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

• Cold injuries

External Links

• emDOCs: Brrr! ED Presentation, Evaluation, and Management of Cold Related Injuries