Frostbite

Basics

Description

  • Localized injury of epidermis and underlying tissue resulting from exposure to extreme cold or contact with extremely cold objects
  • Distal extremities and unprotected areas (i.e., fingers, toes, ears, nose, and chin) most commonly affected
  • Feet and hands account for 90% of frostbite injuries.
    • Severity of injury is based on findings after rewarming (see “Physical Exam”).

Risk Factors

  • Alcohol use
  • Arthritis
  • Atherosclerosis
  • Constricting clothing
  • Diabetes mellitus
  • High altitude
  • Hypothermia
  • Immobilization
  • Improper use of halogenated hydrocarbons (e.g., Freon®, carbon dioxide fire extinguisher)
  • Medications: β-blockers, neuroleptics, sedating drugs
  • Previous cold injury
  • Smoking tobacco
  • Trauma
  • Vasoconstrictive drugs
  • Body parts most affected:
    • Fingers
    • Toes
    • Nose
    • Cheeks
    • Ears
    • Male genitalia
  • Groups at risk:
    • Mentally ill patients
    • Patients with impaired circulation
    • Winter sports enthusiasts and fans
    • Homeless persons
    • Very thin individuals
    • Malnourished people
    • Outdoor laborers
    • Military personnel, especially those of African American and Afro-Caribbean descent, exposed to cold, wet climates
    • Elderly people
    • Infants

General Prevention

  • Avoid prolonged cold exposure whenever possible.
  • Maintain adequate nutrition and hydration when spending time in cold weather.
  • Dress appropriately for cold weather:
    • Dress in layers: Clothing should be made of material that absorbs perspiration and prevents heat loss, such as polypropylene, polyester or synthetic wool, and inner insulation layer such as fleece or wool, and outerwear should be windproof and water repellent but also allow for ventilation and moisture transfer.
    • Cover head, ears, and neck.
    • Mittens help to conserve heat better than gloves.
    • Footwear should be water-repellent and insulated.

Pathophysiology

  • Direct cellular damage can occur from frostbite, as temperature of freezing tissue approaches −2°C.
  • Tissue damage and cell death result from initial freeze injury and inflammatory response that occurs with rewarming.
  • The prefreeze phase consists of tissue cooling, vasoconstriction, and ischemia.
  • In the freeze-thaw phase, ice crystals can form extracellularly (slow freeze) or intracellularly (rapid freeze). This process causes cellular electrolyte shifts, cellular dehydration, cell membrane lysis, and cell death.
  • The thawing phase involves ischemia-reperfusion injury and inflammatory response.
  • In vascular stasis phase, blood vessels constrict and dilate, blood can leak from vessels or coagulate within them.
  • Late ischemic phase involves progressive ischemia and infarction, including the release of inflammatory mediators, especially prostaglandin F2, thromboxane A2, bradykinins, and histamine. There is intermittent vasoconstriction of vessels, emboli production, and thrombi formation, leading to cell death.
  • Most severe injuries are seen in tissues that freeze, thaw, and freeze again.

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