Acute Frostbite

Skin and soft tissue are readily susceptible to injury at either end of the temperature spectrum. With exposure to cold, unprotected tissues can readily become frostbitten and/or hypothermic (aka frostnip); these are two distinct but often linked injuries. In the past, skin, limbs, and digits sustaining severe frostbite injury had predictable outcomes: sloughing or amputation. The only question was how long to wait to amputate. Essentially, no progress was made in the treatment of frostbite until the early 1990s when the development of a treatment protocol for frostbite patients was developed using thrombolytics to restore blood flow to damaged tissue.

Frostbite has two separate mechanisms to the injury itself. The initial insult is the cold injury that leads to direct cellular damage from actual freezing of the tissues. Rewarming of the affected tissues leads to the second, a reperfusion injury resulting in patchy microvascular thrombosis and tissue death.

• There are two classification methods used to determine the severity of frostbite. The traditional classification uses a first- through fourth-degree injury scale, similar to burn injury. Frostnip is the stage just before frostbite, which is chilling of the skin without any cellular damage. It may present with blanched, cool skin that becomes warm and reddened upon rewarming. It often presents with significant but limited discomfort and no evidence of cutaneous damage such as blistering.

  • First-degree frostbite: Superficial damage to the skin from tissue freezing, with redness (erythema), some edema, hypersensitivity, and stinging pain.

  • Second-degree frostbite: Deeper damage to skin, with a hyperemic or pale appearance, significant edema with clear or serosanguineous fluid-filled blisters, and severe pain. Frostnip and first- and second-degree frostbite will generally heal without significant tissue loss.

  • Third-degree frostbite: Deep damage to the skin and subcutaneous tissue. Cold, pale, and insensate without a lot of tissue edema. Shortly after rewarming, edema rapidly forms, along with the presentation of hemorrhagic blisters. Significant pain often occurs after rewarming.

  • Fourth-degree frostbite: All the elements of a third-degree injury with evidence of damage extending to the muscle, tendon, and bone of the affected area.

Determining the extent of frostbite injury starts with a detailed history regarding how the affected area appeared on presentation. The history of a cold, white, and insensate extremity on presentation is consistent with severe frostbite injury (third- and/or fourth-degree frostbite). A severe frostbite injury requires emergent therapy with thrombolytics unless the patient meets one of the exclusion criteria. If in question regarding the depth of the injury, a clinical examination can be supported by a vascular study as indicated. A digital Doppler examination is a simple and quick modality to further clarify the diagnosis of severe frostbite.