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  Address hypothermia, dehydration, and any alternative life threats before focusing on cold-induced tissue injuries.

  
  
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  When in doubt, treat all cold-induced tissue injuries as frostbite.

  
  
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  Rewarm frostbitten extremities rapidly in a warm water bath (40–42°C) and nonfreezing injuries slowly in a dry environment.

  
  
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  Do not discharge patients with cold-induced tissue injuries without first ensuring they have a warm, dry place to go.

Previously the domain of military physicians, the prevalence of cold-induced tissue injuries in the civilian population has increased substantially over the past 20 years as a result of the growth of homelessness and an expanding interest in cold weather outdoor activities such as skiing and mountain climbing. Cold-induced tissue injuries are typically divided into 2 categories: nonfreezing cold injuries (NFCI) and frostbite. Examples of NFCIs include frostnip, chilblains/pernio, and immersion/trench foot. Of the 2 types of injury, frostbite is the more devastating and requires more aggressive treatment. That said, chilblains and immersion foot can also progress to significant disability and require prompt recognition and intervention.

Although individuals at the extremes of age are at a higher risk for cold-induced tissue injuries, frostbite is fairly uncommon in these cohorts. In fact, adults aged 30–49 are the most likely group to suffer frostbite. The hands and feet account for more than 90% of all reported frostbite injuries, whereas almost all NFCIs involve the feet. Other areas of the body at risk for cold-induced tissue injury include the face (eg, nose, ears), buttocks and perineum, and penis.

There are 3 major categories of risk factors for cold-induced tissue injury. Behavioral risk factors include homelessness, inadequate clothing or shelter, alcohol or drug use/intoxication, and psychiatric illness. Physiologic risk factors include comorbid diseases that impair distal circulation (eg, diabetes, vasculitis), the use of vasoconstrictive medications, and external conditions such as high altitude exposure. Mechanical risk factors compose the final category and are the most easily correctable. Common examples include constrictive clothing and jewelry, prolonged contact with heat conductive materials, and immobility.

Of the 3 types of NFCI, frostnip is the least severe. It typically affects the distal extremities after prolonged exposure to cold but nonfreezing temperatures. Ice crystal formation and profound vasoconstriction are common in the superficial tissues, and patients frequently complain of a dull throbbing pain during rewarming. Essentially a precursor to frostbite, overt tissue destruction is lacking.

Chilblains (pernio) involve the formation of inflammatory skin lesions after repeated intermittent exposure to a nonfreezing but cold and wet environment. Although chilblains can affect any area of the body, the face, dorsal surfaces of the hands and feet, and pretibial tissues are the most commonly involved. Permanent tissue damage secondary to vascular inflammation and tissue bed hypoxia may develop. Women, children, and patients with underlying vasculitides are most commonly affected.

Immersion foot develops after the prolonged exposure to persistently wet conditions, both warm and cold, although the latter typically results in more severe tissue injury. The long-term exposure to moisture induces tissue edema and inflammation, whereas the prolonged cold exposure leads to direct tissue injury. The consequently encountered vasospasm, intravascular thrombosis, and neuronal destruction can lead to full-thickness tissue loss. Immersion foot is most commonly seen in the homeless population.

Frostbite involves the freezing of tissues and can result in significant tissue loss and long-term disability. Ice crystal formation within the extracellular space can induce intracellular dehydration, enzymatic dysfunction, and cellular death. Microvascular occlusion secondary to profound vasospasm and intraluminal thrombosis further the severity of tissue loss. Circulating tissue inflammatory markers frequently exacerbate the intensity of tissue injury and complicate the reperfusion of warmed tissue.

History

Taking an adequate history should never delay the removal of a patient from a cold environment. Inquire about previous medical or psychiatric illnesses, drug and alcohol use, and housing status. Any history of trauma should be documented. Try to identify the overall duration of cold exposure and elicit any previous history of frostbite or a thawing and refreezing pattern of tissue injury. The review of symptoms should attempt to discover the presence of altered sensitivity, numbness, or burning pain.

Frostnip generally presents with numbness, pain, pallor, and paresthesias of the ears, nose, fingers, and toes. Patients with chilblains typically present with complaints of erythema, edema, and an intense pruritus or burning sensation. Immersion foot is usually associated with significant pain and swelling and occasionally numbness and/or the inability to ambulate. Frostbitten patients generally complain of the inability to feel the affected areas.