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For further information, see CMDT Part 37-07: 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 ...

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