Frostbite

Descriptive text is not available for this imageBASICS

DESCRIPTION

  • Frostbite is a thermal injury that occurs when body tissues are exposed to temperatures below their freezing point.
  • Feet (85%) and hands (5%) account for 90% of recorded injuries.
    • Other commonly involved body parts: nose, cheeks, ears, penis

EPIDEMIOLOGY

  • Some trend toward increased incidence over the past 20 years
    • Unclear if due to increased reporting, more extreme temperatures related to climate change, or increased number of individuals with risk of frostbite
  • Children and elderly are at increased risk of hypothermia and frostbite, although they make up a minority of reported cases.
  • Most reported cases occur within the 30 to 49 years age group.
  • Men are affected more than women at a rate of almost 10:1.
  • Recent review of the National Trauma Data Bank and National Burn Repository found 388 cases over an 8-year period and 497 cases over a 10-year period, respectively.

ETIOLOGY

  • Wind chill, as well as absolute temperature, plays a role in the temperature experienced by the body’s tissues.
  • Degree of irreversible damage is more related to the length of time the tissue remains frozen than the absolute temperature.

RISK FACTORS

  • Military activities
  • Homelessness
  • Psychiatric illness
  • Alcohol consumption
  • Illicit drug use
  • Inadequate clothing and protective equipment
  • Winter sports
  • Smoking
  • Peripheral vascular disease
  • Medications (β-blockers, sedatives, neuroleptics)
  • Working with equipment that uses nitrogen dioxide (NO2) or carbon dioxide (CO2)
  • High altitude

GENERAL PREVENTION

  • Adequate clothing and multiple loose protective layers
    • Mittens preferred to finger gloves
    • Insulated hat that covers the ears
    • Appropriate fitting, insulated boots
  • Stay dry
  • Avoid prolonged cold exposure (specifically <−15°C).
  • Adequate nutrition and hydration
  • Alcohol and tobacco avoidance
  • Use of supplemental oxygen (O2) in high-altitude (>7,500 m) conditions
  • Use of chemical hand and foot warmers

PATHOPHYSIOLOGY

  • Can be considered to occur in two phases—direct cellular injury at the time of cold exposure and indirect cellular injury as a result of progressive dermal ischemia
  • Direct cellular injury
    • Localized vasoconstriction, increased blood viscosity, and microvascular damage occur in the setting of freezing temperature.
    • Ice crystals form both intracellularly and extracellularly.
    • Crystals damage the cell membrane and change the osmotic gradient resulting in cell dehydration, electrolyte disturbance, denaturation of lipid–protein complexes, and cell death.
    • Triggers a proinflammatory cytokine release
  • Indirect cellular injury
    • More severe than direct cellular injury
    • After thawing, endothelial damage, microvascular thrombosis, inflammatory response, and free radical formation result in ischemia, further cellular injury, and death.

COMMONLY ASSOCIATED CONDITIONS

  • Hypothermia
    • Core body temperature <35°C
    • Occurs in 12% in people with frostbite
  • Trauma
    • 19% of patients with frostbite have been involved in a serious traumatic incident.

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