Frostbite, Frostnip

  • Definitions
  1. Frostbite
    1. Skin (and deeper structures) freeze resulting in tissue injury
  2. Frostnip
    1. Superficial ice crystals deposit on the skin surface without tissue injury
    2. Self-limited hyperesthesia, Paresthesia and pallor in response to cold, and resolves within 10 minutes
    3. Typically occurs on the face (nose, ears) and extremities (fingers, toes), as well as genitalia
    4. If not addressed with warming measures (e.g. mittens, hat, going indoors), may progress to Frostbite
  • Risk Factors
  1. Peripheral Vascular Disease
  2. Peripheral Neuropathy (e.g. Diabetic Neuropathy)
  3. Prolonged cold or moisture exposure
  4. High wind (high wind chill)
  5. High altitude
  6. Inadequate clothing
  7. Malnutrition
  8. Extremes of age
  9. Vasoconstrictive agents (e.g. Nicotine)
  10. Altered Mental Status
  1. Room Temperature
    1. Normal skin perfusion >200 ml/min
  2. Skin Temperature 59 F (15 C)
    1. Skin perfusion 20-50 ml/min
    2. Vasoconstriction interrupted by periods of vasodilation lasting 5-10 minutes each, recurring every 15-20 minutes
  3. Skin Temperature 50 F (10 C)
    1. Skin Sensation lost (Neuropraxia)
  4. Skin Temperature 32 F (0 C)
    1. Minimal skin perfusion
    2. Skin Temperature drops each minute by 0.9 F (0.5 C)
  5. Skin Temperature <31.1 F (-0.5 C)
    1. Intra and extracellular water crystals form, disrupting membranes and Protein structures
    2. Osmotic gradient and Electrolyte shifts occur and ultimately lead to cell death
    3. Vascular stasis and ultimately tissue ischemia and necrosis
    4. Inflammatory response on rewarming with risk of thrombosis and reperfusion injury
  • Pathophysiology
  • Stages of Frostbite
  1. Pre-freeze
    1. Starts at Temperatures 50 F (10 C)
    2. Superficial tissues are cooled
  2. Freeze-thaw
    1. Intra and extracellular water crystals form, disrupting membranes and Protein structures and cell death
    2. Thawing may lead to inflammatory response and reperfusion injury
  3. Vascular stasis
    1. Vasoconstriction alternates with vasodilation resulting in vessel leaks and intravascular coagulation
  4. Tissue ischemia and necrosis
    1. Intravascular thrombosis with secondary tissue ischemia and infarction
  • Grading
  • Classification - 4 category (similar to Burn Injury classification)
  1. Precautions
    1. Classification should only be applied after rewarming is complete
    2. Accurate classification may be delayed for first 1-3 months
  2. First-degree Frostbite (superficial skin)
    1. No Cyanosis or Blisters
    2. Numb, erythematous skin
    3. May develop yellow-white Plaques
    4. Tissue may slough
  3. Second-degree Frostbite (full skin thickness)
    1. Clear to milky fluid-filled bullae (Blisters) by 48 hours
    2. Surrounding edema and erythema forms in the first 24 hours after injury
    3. Cyanosis limited to distal phalanx
    4. If occurs at altitude, elevation >4000 m (13000 ft), injury worse than grading due to tissue Hypoxemia
  4. Third-degree Frostbite (full skin thickness AND subcutaneous tissue involvement)
    1. Hemorrhagic vessicles to bullae (Blisters) by 48 hours
    2. Cyanosis of proximal phalanx
    3. High risk for amputation
  5. Fourth-degree Frostbite (full skin thickness AND Muscle/bone involvement)
    1. Full thickness tissue loss and gangrene
    2. Cyanosis on carpal regions of the wrist and the tarsal regions of the foot
    3. Mottled, deep red or cyanotic skin
    4. Bone and Muscle freezing
    5. Dry, black mummified skin
    6. Ultimately requires amputation in almost all cases
  • Grading
  • Classification - 2 category (preferred in the acute setting)
  1. Distribution - high risk areas
    1. Extremities (hands, feet)
    2. Face (ears, nose)
    3. Genitalia (penis)
  2. Superficial Frostbite (includes first and second degree Frostbite as above)
    1. Erythema and edema
    2. Minimal to no tissue loss
    3. No hemorrhagic bullae (but clear or milky bullae may be present)
  3. Deep Frostbite (includes third and fourth degree Frostbite as above)
    1. Woody-feel to skin
    2. Hemorrhagic bullae
    3. Tissue loss (including bone and Muscle injury)
    4. Mummification or amputation
  • Imaging
  1. Indications
    1. Assess for Tissue Plasminogen Activator (tPA) indications in severe Frostbite immediately after rewarming
    2. Assess prognosis at <48 hours (amputation risk)
    3. Define surgical margins at time of amputation
  2. Modalities
    1. Angiography
    2. Technetium-99m Pyrophosphate Scintingraphy (Tc Scintingraphy)
    3. MRI
  • Management
  • Acute
  1. Precautions
    1. Hypothermia Management take precedence over Frostbite management
    2. Do not rewarm if chance of refreezing (risk of freeze-thaw injury, inflammation, thrombosis, cell death)
    3. Do not rub or massage skin
    4. Clear any evaporative liquids (e.g. gas, Alcohol)
    5. Avoid external dry heat (e.g. fire, radiator)
  2. Initial measures
    1. Remove all jewelry and wet clothing
    2. Rapid rewarming in warm (40-42 C, 104-107.6 F) water bath for 15-30 min
      1. Some guidelines recommend 98.6 to 102.2 F (37 to 39 C) bath for 30-60 min
      2. Do not use water hotter than 107.6 F (42 C) due to Thermal Burn injury risk
      3. Continue until skin is pliable, soft, red or purple
    3. Elevate involved area (decrease edema)
    4. Protect the injured limb with padding
    5. NSAIDS (e.g. Ibuprofen)
      1. Helps prevent reperfusion injury
    6. Opioid Analgesics (esp. for rewarming)
    7. Topical aloe vera applied to thawed tissue every 6 hours
    8. Tetanus Prophylaxis
    9. Consider aspirating clear or milky bullae
      1. Do not aspirate or debride hemorrhagic bullae or tissue (may dessicate deeper tissue injury)
    10. Daily Hydrotherapy (30 to 45 minutes at 40 C, 104 F) improves range of motion and function
    11. Avoid antibiotics unless open or dirty wounds are present, or signs of infection
  3. Other measures (discuss with local consultants)
    1. Tissue Plasminogen Activator (tPA)
      1. Has been used for deep Frostbite within first 24 hours to reduce risk of amputation
      2. May be directed by Angiography or Tc Scintigraphy performed immediately after rewarming
      3. See Thrombolytic for contraindications
      4. Heparin is typically used after tPA
      5. Iloprost (Ventavis) may also be used as adjunct to tPA
        1. Vasodilator used for up to 48 hours in severe cases to prevent thrombosis
      6. References
        1. Ibrahim (2015) J Burn Care Res 36(2): e62-6 [PubMed]
    2. Hyperbaric oxygen
  4. Disposition
    1. Hospital observation for moderate to severe injuries
    2. Monitor for Compartment sydrome, Rhabdomyolysis and Renal Failure
  • Management
  • Longterm
  1. Refer deeper Frostbite to wound care or burn specialist
  2. Indications for transfer or referral to higher level of care (e.g. burn center)
    1. Deep Frostbite
    2. Extensive limb involvement
    3. Concerns for Compartment Syndrome (if unable to manage locally)
  3. Surgical Management
    1. Delay surgical amputation or Debridement for 1-3 months until demarcation of mummified areas
    2. Earlier Debridement or amputation may be needed if refractory superinfection occurs (esp. gangrene)
  • Complications
  1. Compartment Syndrome
  2. Excessive sweating
  3. Cool extremities
  4. Numbness
  5. Abnormal color
  6. Nail Disorder
  7. Skin Pigment Changes
  8. More susceptible to second injury
  9. Limb Amputations (4th degree, mummified tissue)
  • Prevention
  1. See Prevention of Cold Weather Injury
  2. See Emergency Car Kit
  3. Never ignore numbness in a cold extremity
  • Images
  1. Presentation Graphic
    1. erEnvironFrostbite.jpg
  • References
  1. Civitarese and Sciano (2018) Crit Dec Emerg Med 32(2): 3-16
  2. Rathjen (2019) Am Fam Physician 100(11): 680-6 [PubMed]