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Frostbite

BASICS

  • Localized severe cold injury with tissue freezing causing direct cellular injury and progressive dermal ischemia.
  • Commonly affects exposed hands, feet, face, ears.
  • Synonyms: Dermatitis congelationis, freezing cold injury (FCI).

EPIDEMIOLOGY

  • Predominantly adults; can affect all ages.
  • More common in females possibly due to increased surface area relative to body mass despite greater male exposure.

ETIOLOGY AND PATHOPHYSIOLOGY

  • Prolonged cold exposure leads to ice crystal formation intra- and extracellularly.
  • Vasoconstriction reduces blood flow; endothelial injury worsens ischemia.
  • Cellular dehydration alters electrolytes, causing cell death.
  • Severe injury extends into muscle and bone causing necrosis and mummification.
  • Rewarming leads to edema, blisters due to inflammatory mediators (prostaglandins, thromboxane A2).
  • Refreezing after thaw worsens injury.
  • Chronic inflammation may cause delayed healing due to macrophage imbalance.

RISK FACTORS

  • Prolonged exposure to freezing temperatures, wind, water exposure.
  • High-altitude activities (mountaineering).
  • Military cold environment operations.
  • Constrictive or wet clothing, inadequate insulation.
  • Altered mental status (alcohol, drugs, psychiatric illness).
  • Homelessness, previous cold injury.
  • Dehydration, malnutrition, endocrine or skin conditions affecting heat retention.
  • Hypothermia, smoking, Raynaud's, diabetes, peripheral vascular disease.

GENERAL PREVENTION

  • Dress in layers with proper cold weather gear; avoid constrictive clothing.
  • Cover exposed skin and extremities; stay dry.
  • Avoid alcohol, caffeine, vasoconstrictive medications.
  • Maintain hydration and caloric intake.
  • Use chemical/electric warmers as needed.
  • Monitor wind chill and temperature exposure.
  • Avoid emollients on exposed skin.
  • Exercise cautiously to maintain warmth.

COMMONLY ASSOCIATED CONDITIONS

  • Hypothermia
  • Alcohol/drug abuse

DIAGNOSIS

History

  • Assess cold exposure duration and severity.
  • Symptoms: throbbing pain, paresthesias, numbness, loss of coordination/dexterity.

Physical Exam

  • Typical sites: hands, feet, face, ears.
  • Before rewarming: insensate, white/gray-yellow, cyanotic, hard/waxy skin.
  • After rewarming: graded by cyanosis extent (Grade 1-4) or burn-like degrees (1st to 4th degree).
  • 1st/2nd degree: superficial injury (erythema, blisters).
  • 3rd/4th degree: deep injury with hemorrhagic blisters, necrosis, muscle/bone involvement.

Differential Diagnosis

  • Frostnip (superficial, no tissue loss).
  • Chilblains/pernio (inflammatory, no freezing).
  • Immersion foot/trench foot.
  • COVID toes (pernio-like lesions).

DIAGNOSTIC TESTS & INTERPRETATION

  • Baseline labs: CBC, CMP, urinalysis for myoglobinuria, wound culture if infection suspected.
  • Radiography for soft tissue vs bone involvement.
  • Tc-99m bone scan to assess tissue viability, guide thrombolysis or amputation.
  • MRI/MRA, duplex US, angiography for severe cases.
  • Serial photography to monitor progression.
  • Angiography effective for amputation decision; caution in renal insufficiency.
  • SPECT/CT for prognosis.

TREATMENT

General Measures

  • Correct hypothermia; remove jewelry.
  • Rewarm only if no refreezing risk: water bath 37-39°C for ~30 minutes until pliable/red/purple.
  • Avoid direct heat sources (fire, heaters).
  • Apply topical aloe vera gel pre-dressing.
  • Drain clear/cloudy blisters selectively; leave hemorrhagic intact.
  • Splint, elevate extremity.
  • Tetanus prophylaxis.
  • Hydration: oral if alert/no GI symptoms; IV warm saline if needed.
  • Daily warm bathing and mobilization.
  • Use dry, loose dressings.
  • Pain control with NSAIDs, narcotics as needed.
  • Antibiotics only for infection.

Medication

  • First Line:
  • Tissue plasminogen activator (tPA) IV or intraarterial within 24 hours for deep frostbite (Grade 3-4) to reduce microvascular thrombosis and amputation risk.
  • Heparin adjunct with tPA; not monotherapy.
  • Ibuprofen 400 mg q12h (prostaglandin inhibition).
  • Update tetanus toxoid.
  • Second Line:
  • Pentoxifylline 400 mg q8h.

Additional Therapies

  • Heated oxygen.
  • Warm IV fluids.
  • Botulinum toxin injections for chronic pain sequelae.

Surgery/Other Procedures

  • Fasciotomy if compartment syndrome develops.
  • Surgical debridement as needed for necrotic tissue.
  • Amputation only after clear necrosis demarcation (4-12 weeks).
  • Imaging guides surgery timing and extent.

ADMISSION & NURSING

  • Hospitalize unless Grade 1 frostbite with no blisters.
  • Treat in trauma/burn center experienced in frostbite care.
  • Administer tPA in ICU setting.
  • Manage hydration, nutrition, pain, wound care.

ONGOING CARE

  • Protect affected parts.
  • Continue physical therapy.
  • Avoid smoking, alcohol, repeat cold exposure.
  • Ensure proper clothing and footwear fit.
  • Monitor pediatric growth if involved extremities.

PATIENT EDUCATION

  • Teach frostbite prevention, risk factors, early symptoms.
  • Proper field management of cold injuries.

PROGNOSIS

  • Grade 1: no amputation, no sequelae.
  • Grade 2: possible soft tissue/nail amputation.
  • Grade 3: possible digit bone amputation, functional impairment.
  • Grade 4: possible limb bone amputation, major functional loss.
  • Worse prognosis with longer exposure and substance abuse.

COMPLICATIONS

  • Tissue necrosis, spontaneous amputation.
  • Gangrene.
  • Hyperhidrosis from nerve injury.
  • Raynaud phenomenon.
  • Frostbite arthropathy, osteoarthritis.
  • Chronic neuropathic pain.
  • Localized osteoporosis.
  • Premature epiphyseal closure in children.

REFERENCES

  1. Fudge J. Preventing and managing hypothermia and frostbite injury. Sports Health. 2016;8(2):133-139.
  2. Gao Y, Wang F, Zhou W, et al. Research progress in the pathogenic mechanisms and imaging of severe frostbite. Eur J Radiol. 2021;137:109605.
  3. McIntosh SE, Hamonko M, Freer L, et al; Wilderness Medical Society. Practice guidelines for prevention and treatment of frostbite. Wilderness Environ Med. 2011;22(2):156-166.
  4. Volansky R. Diagnosing “COVID toes” and other challenges in the derm-rheum overlap. Healio Rheumatology, 2021.
  5. Hickey S, Whitson A, Jones L, et al. Guidelines for thrombolytic therapy for frostbite. J Burn Care Res. 2020;41(1):176-183.

CODES

  • ICD10: T33.90XA Superficial frostbite, initial encounter
  • ICD10: T34.90XA Frostbite with tissue necrosis, initial encounter
  • ICD10: T33.829A Superficial frostbite of foot, initial encounter

CLINICAL PEARLS

  • Frostbite is tetanus-prone; provide tetanus prophylaxis.
  • Avoid rewarming if risk of refreezing; rewarm only with water.
  • Assess for additional injuries on insensate areas.
  • Use tPA within 24 hours in appropriate cases to reduce amputations.
  • Early injury severity assessment difficult; delay surgery until necrosis clearly demarcated (4-12 weeks).