Frostbite

Key Features

Essentials of Diagnosis

• Injury is due to freezing and formation of ice crystals within tissues

General Considerations

• Can be divided into four tiers, or "degrees" of injury, which can be established by differences in imaging after rewarming

  • First-degree frostbite results in numbness and erythema; injured areas may show mild epidermal sloughing without gross tissue infarction

  • Second-degree injuries exhibit superficial skin vesiculation with clear or milky fluid-filled blisters surrounded by erythema and edema

  • Third-degree frostbite results in deeper hemorrhagic blisters, extending beneath the dermal vascular plexus

  • Fourth-degree injuries extend completely through the dermis with necrosis extending into muscle and bone

• Alternatively, a two-tier classification may be used in the field after rewarming and before imaging and is similar to thermal burns

  • Superficial (first- and second-degree injuries) with no or minimal anticipated tissue loss

  • Deep (third- and fourth-degree injuries) with anticipated tissue loss

• Localized hypothermia, vasoconstriction, and slowed metabolism occur as temperature falls below 25°C, although oxygen demand may increase if activity continues

• Once tissue is frozen it becomes pain free

• Most tissue destruction follows the reperfusion of the frozen tissues, with damaged endothelial cells and progressive microvascular thrombosis resulting in further tissue damage

Clinical Findings

Symptoms and Signs

Mild cases

• Only the skin and subcutaneous tissues are involved

• The symptoms are numbness, prickling, itching, and pallor

Severe cases

• With increasing severity, deep frostbite involves deeper structures

• There may be paresthesia and stiffness

• Thawing causes tenderness and burning pain

• Skin is white or yellow, loses its elasticity, and becomes immobile

• Edema, hemorrhagic blisters, necrosis, and gangrene may appear

Diagnosis

Imaging Studies

• MRI with magnetic resonance angiography and technetium scintigraphy can assess the degree of involvement and distinguish viable from nonviable tissue

Treatment

Medications

• NSAIDs should be administered (in the absence of contraindications) until frostbite wounds are healed or surgical management occurs (usually for 4–6 weeks)

• Thrombolytic therapy

  • Should be reserved for deep injuries with the potential for significant morbidity

  • Must include a risk-benefit analysis prior to administration of the medication by experienced providers in a facility with intensive care capabilities

• Rates of amputation have been reduced with the use of

  • Intravenous infusions of synthetic prostaglandins

  • Tissue plasminogen activators

  • Intra-arterial administration of a thrombolytic within 24 hours of exposure

• The rate of tissue salvage decreases with every hour of delay from rewarming to thrombolytic therapy

Therapeutic Procedures

• Treat associated systemic hypothermia (see Hypothermia)

• Monitor fluids and electrolytes

• Superficial frostbite (frostnip) of extremities

  • In the field, apply firm steady ...