A 58-year-old man presents to the emergency department (ED) with blister formation on both feet that he first noticed 2 days ago. He denies past medical history, medication use, or drug allergies. His social history is significant for alcohol dependence and he recently became homeless. He denies any sick contacts or recent travel. Upon physical examination, the lesions are fluid-filled. His feet are grossly cyanotic and tender to the touch. Pulses are present by Doppler. His foot is shown below. What is the most likely diagnosis?
(Reproduced, with permission, from Knoop KJ, Stack LB, Storrow AB. Atlas of Emergency Medicine. New York, NY: McGraw Hill; 2002:517.)
e. Herpes simplex infection
The answer is b. Frostbite usually occurs when tissue temperature falls below 0°C (32°F). There are three phases to the freezing injury cascade. Phase 1 (prefreeze, without actual ice formation) occurs when the tissue reaches a temperature below 10°C and includes initial skin cooling, increased blood viscosity, vasoconstriction, and microvascular leakage that causes localized edema formation. Patients typically lose cutaneous sensation in the tissue during this phase. Phase 2 (freeze-thaw) occurs when extracellular crystal formation begins, thereby causing intracellular shrinkage, protein and lipid derangements, cell dehydration, and collapse of the cellular network. Finally, phase 3 (vascular stasis and progressive ischemia) begins once the tissue is rewarmed and involves further coagulation, interstitial leakage, cytokine release, and cell death. This results in blister formation, cyanosis, and ultimately mummification of the tissue. The bullae formed may also have a hemorrhagic appearance, but not always. It is important to note that wind and moisture may increase the freezing rate. Management includes rapid rewarming in a circulating water bath with water temperatures of 37°C to 39°C. Tissue massage, which furthers tissue loss, should be avoided as should dry heat sources, such as a space heater. Rewarming is a painful procedure that requires parenteral analgesia. Patients may also have a degree of dehydration and benefit from warmed crystalloid administration.
Chilblains (a), also known as pernio, is an abnormal vascular response to cold resulting in erythema, itching, and inflammation of the skin. Pernio is commonly seen in the homeless population as a result of chronic dry-cold exposure and mostly affects the face, hands, and pretibial areas, particularly in young women or those with autoimmune disorders Trench foot (c), also known as immersion injury, is also common in the homeless population. This occurs when skin is exposed chronically to wet and cold environments; however, the ambient temperature is above freezing. It usually presents as a loss of sensation with pallor ...