There is a correlation between the length of time tissue is frozen and the degree of cellular damage. Rapid rewarming is the single most effective therapy for frostbite. However, rewarming in the field is often impractical and is sometimes dangerous. In fact, in some unusual circumstances, it is best to endeavor to keep the affected part frozen until definitive care can be administered. For instance, if the victim has frozen feet and the only avenue to evacuation is prolonged ambulation, then rewarming can significantly complicate matters. The risk of refreezing the feet and causing even more severe damage is a real concern. Also, if adequate analgesia is not available, the rewarming process itself can be excessively painful. Ambulation on edematous and blistered feet may not be possible because of pain. In extreme situations such as this, it may be wise to keep the feet frozen and ambulate the patient to a location where more advanced evacuation can occur. If rewarming is attempted in the field, only clean water warmed to 40° to 42°C (104° to 107.6°F), as measured by thermometer, should be used. The use of hot, untested tap water should be avoided because the 50° to 60°C (122° to 140°F) temperatures will cause a destructive thermal injury and worsen the prognosis. Attempts to directly warm with dry air, such as campfires and heaters, should be avoided. Dry heat tends to desiccate damaged tissue, and temperature cannot be adequately measured. Adding a thermal injury to frostbite will worsen the outcome. Rubbing snow on frostbitten tissue to stimulate circulation is ineffective, destructive, and absolutely contraindicated.
Controversy surrounds management of the blisters associated with frostbite. Clear blisters are rich in tissue-injurious thromboxane and prostaglandins. Common sense suggests that blister débridement or aspiration would limit contact with these chemicals and allow direct contract with aloe vera (Dermaide Aloe Cream) to countereact their injurious effects. Also, tense blisters, which tend to only worsen when immobilization is not possible, are painful. Débridement or aspiration can bring some pain relief. When the patient is ambulating on rewarmed, frostbitten feet, the associated blisters often rupture anyway. Field débridement of clear blisters is controversial, but adequate research is lacking to support or condemn this practice. Hemorrhagic blisters should not be drained in the field.
One possible complication of field aspiration or débridement is the theoretical increased risk of infection. Prophylactic use of penicillin might be wise in the field setting to combat any potential wound infection. Wounds should be cleansed daily, and, if feet are involved, socks should be clean and changed at least once or twice per day. Affected digits should be covered with aloe vera and separated by dry, sterile cotton and dressings should be changed daily. Pain management should begin with nonsteroidal anti-inflammatory drugs, such as ibuprofen 12 mg/kg/day in divided doses, to counteract the arachidonic acid cascade and should be continued even if opioids analgesics are required as well. The victim should be discouraged from smoking because it exacerbates vasoconstriction and tissue damage. ll0.,11,,11
EMERGENCY DEPARTMENT MANAGEMENT In taking the patient's history, it is important to determine as many prognostic factors as possible. What was the temperature and wind velocity? How long was the extremity frozen, and, if it was thawed, did any refreezing occur? Was there any self-treatment, such as rubbing with snow or use of aloe vera or ibuprofen? Were recreational drugs, alcohol, or tobacco involved? Are there any predisposing medical conditions?
Frostbite is often associated with systemic hypothermia and dehydration, both of which can have a negative impact on the prognosis for tissue salvage. Rehydration and general warming are important adjuncts to therapy when indicated.
Frostbitten patients often present to the emergency department subacutely (>24 h after injury) and with the involved extremity in a partially thawed state. This more prolonged injury and slow, partial thawing usually translates to significantly longer hospital stays and greater tissue loss. However, this should not mean the patient is treated any less aggressively than the acute patient. The target of treatment remains minimizing tissue loss by focusing on the zone of stasis, where damaged but potentially salvageable tissue exists.
Rapid rewarming is the core of frostbite therapy and should be initiated as soon as possible. The injured extremity should be placed in gently circulating water at a temperature of 40° to 42°C (104° to 107.6°F) for approximately 10 to 30 min, until the distal extremity is pliable and erythematous. Frostbitten faces can be thawed using moistened compresses soaked in warm water. Some patients may tolerate immersion of their ears in a bowl or pool of warmed water. Anticipate severe pain during rewarming and titrate with parenteral narcotics. The patient will probably require daily hydrotherapy and physical therapy during the inpatient phase.
Blister management is somewhat controversial, as is the use of prophylactic antibiotics. The current consensus is that clear blisters should be débrided or at least aspirated. The blister fluid is rich in destructive thromboxane and prostaglandins. Removal limits damage from these chemicals and enables access to the underlying tissue for topical therapy. Hemorrhagic blisters should not be débrided because this often results in tissue desiccation and worsened outcome. However, there is some controversy as to whether aspiration is helpful. Both blister types should be treated with topical aloe vera (Dermaide Aloe Cream) q6h, which helps to combat the arachidonic acid cascade. Affected digits should be separated with cotton and wrapped with sterile, dry gauze. Elevation of the involved extremities helps decrease edema and pain.
The role of prophylactic antibiotics is unclear. The edema associated with the first several days after injury does appear to predispose to infection. Staphylococcus aureus, Staphylococcus epidermidis, and b-hemolytic streptococci account for nearly half of infections, but anaerobes, Pseudomonas, and Enterococcus are important pathogens as well. Therapy with penicillin G 500,000 U intravenously q6h, for 48 to 72 h, is recommended in several successful protocols and seems to be beneficial. One study, however, demonstrated better infection prophylaxis using topical bacitracin. Silver sulfadiazine (Silvadene) cream has also been advocated by some, but it has not been shown to be consistently beneficial. One disadvantage of using topical antibiotics is that it complicates the concurrent use of aloe vera (Dermaide Aloe Cream). It is important to address tetanus status and administer appropriate vaccination, if needed, because frostbite is a tetanus-prone wound.
Several agents besides aloe vera (Dermaide Aloe Cream) have been advocated to battle the arachidonic acid cascade and thereby limit tissue damage. The most commonly advocated oral medication is ibuprofen at a daily dose of 12 mg/kg. Animal studies suggest possible future roles for oral methimazole, a thromboxane synthetase inhibitor, and topical 1% methylprednisolone acetate, which acts as a phospholipase A 2 inhibitor, preventing the formation of arachidonic acid.
Another controversial area is the use of sympathectomy to relieve vasospasm and edema. The treatment may be medical, as in the use of intraarterial reserpine, or surgical. There is no role for early sympathectomy, and the controversy is beyond the scope of emergency department management.
Heparin, and hyperbaric oxygen therapy have been studied and appear to be of little value. To date; frostbite treatment with intravenous low-molecular-weight dextran has not been studied clinically in human, but anecdotal reports have been encouraging. Some preliminary data from a study using intraarterial recombinant tissue plasminogen activator in patients with third-degree frostbite suggest that it may hold some promise in decreasing the rate of amputation. 15 A recent limited study suggests that the prostaglandin E-, analogue limaprost may be an effective prophylactic and therapeutic vasodilator for local cold injuries at high altitudes. 16
Early surgical intervention is not indicated in the management of frostbite. Premature surgery has been an important contributor to necessary tissue loss and poor results in the past. This is primarily due to the inability to assess the depth of frostbite at early stages and the fact that the blackened, mummified carapace is protective of the underlying regenerating tissue. Limited, early escharotomy may be indicated if the eschar is preventing adequate range of motion or circulation. Fasciotomy is rarely, if ever, indicated. Amputation may be unavoidable, however, if wet gangrene or infection complicates recovery. It usually takes at least 3 to 4 weeks for full demarcation to occur. Most amputations and grafts occur during the third week. The mean length of hospital stay for all degrees of frostbite is reported to be 8.5 days to 33.2 days. To minimize extended hospital stays, some have advocated the early use of radionuclide angiography with bone scan at 7 to 14 days to assess tissue viability and possible early surgical débridement. —I8 However, a recent case report suggests that the use of magnetic resonance imaging with magnetic resonance angiography may prove to be more helpful in the early determination of the degree of tissue damage and the eventual prognosis. 19
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