Frostbite

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

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

Imaging Studies

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

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 pressure with warm hand (without rubbing)

  • Place fingers in the armpits

  • Remove footwear, dry the feet, rewarm, cover with adequate dry socks or other protective footwear

• Frostbite

  • If there is a possibility of refreezing, frostbitten part should not be thawed, even if it means prolonged walking on frozen feet; refreezing increases tissue necrosis

Rewarming

• Rapid thawing at temperatures slightly above body heat may significantly decrease tissue necrosis and reverse the tissue crystallization

• Immerse the frozen extremity for several minutes in a moving-water bath heated to 37–39°C for approximately 30 minutes until the area becomes soft and pliable to the touch

• Dry heat (eg, stove or open fire) is not recommended because it is more difficult to regulate

• After thawing, and the part has returned to normal temperature (usually in ~30 min), discontinue external heat

• Rewarming by exercise, rubbing, or friction is contraindicated in the early stage

Protection

• Avoid pressure, friction, physical therapy in early stage

• Keep patient on bed rest, with affected parts elevated and uncovered at room temperature

• Protect skin blebs from physical contact

• Wounds must be kept open and allowed to dry before applying dressings

• Nonadherent sterile gauze and fluffy dressing must be loosely applied to wounds and cushions used for all areas of pressure

• Topical aloe vera cream or gel should be applied to the thawed tissue before application of dressings

• Whirlpool therapy at 37–39°C twice daily for 15–20 min for ≥ 3 weeks helps cleanse skin and débrides superficial sloughing tissue

Surgery

• Débridement and amputation should be considered if it is established that the tissues are necrotic

• Clinicians must watch for evidence of compartment syndrome and need for fasciotomy

• Eschar formation without evidence of infection (even with black eschar formation) may be conservatively treated

Follow-Up

• Gentle, progressive physical therapy to promote circulation should be instituted as tolerated

• Patient education should include ongoing care of the cold injury and prevention of future cold injury

Complications

• Loss of fingers, toes, extremities, tip of nose

• Increased susceptibility to discomfort in the involved extremity upon reexposure to cold with pain, numbness, tingling, hyperhidrosis

• Cold sensitivity of the extremities and nerve conduction abnormalities may persist for years after the cold injury

Prognosis

• Depends on the tissue damage caused by the extent of initial injury, the reperfusion injury during rewarming, and the late sequelae (such as kidney injury or postinjury infection)

When to Admit

• Management of tissue damage, comorbidities, associated injuries

• Need for hospital-based interventions, such as thrombolytics or surgery

• Psychosocial factors (cognitive impairment, inadequate living situation), which could compromise patient safety or recovery