Assessment
When a patient presents to the ED suffering from suspected frostbite, the following should be considered:
Risk factors
Factors predisposing patients to frostbite can be classified into environmental, medical [8] and demographic factors.
| Environmental | Medical | Demographic |
|---|---|---|
|
|
|
Mechanism and pathophysiology
Arteriovenous anastomoses in the skin shunt blood away from acral areas to limit radiative heat loss.
When tissue temperature drops below 10oC, anaesthesia develops. Endothelial cells leak plasma and microvascular vasoconstriction occurs.
Crystallisation is not seen while the deeper tissues conduct and radiate heat.
As tissue temperature continues to fall, ice forms extracellularly, causing water to exit from the cell and inducing cellular dehydration, hyperosmolarity, collapse and death.
History
The patient will typically complain of a coldness or firmness affecting the frostbitten area.
They may also note a stinging, burning or numbness and a clumsiness of the distal extremity [9].
Physical examination
The hands and feet are the most commonly affected areas, although the face and shins may also be involved.
- Superficial features are erythema, oedema, waxy appearance and hard white plaques; sensory deficit is commonly seen
- Deep features are full-thickness damage affecting muscles, tendons and bone, with resulting tissue loss
- Other features include excessive sweating, hyperaemia and tissue gangrene
Diagnosis
The diagnosis of frostbite is a clinical one, although imaging may help to assess severity.
Routine x-ray at presentation and again at 4-10 weeks post-injury may demonstrate specific abnormalities, such as osteomyelitis [10].
The best imaging strategy is scintigraphy. Technetium 99 (Tc-99m) pertechnetate scintigraphy is sensitive and specific for tissue injury.
There is good correlation between scintigraphy findings at 48 hours after injury and ultimate extent of deep-tissue injury [11].
Scintigraphy is also useful in assessing the response of damaged tissue to therapy [12].
Learning bite
Avoid commencing rewarming of the frostbitten extremity unless it is clear that the process will not be interrupted.