COLD INJURY/FROSTBITE

Rapid Re-warming and Re-establishment of Perfusion

The mainstay of treatment of the cold injury is re-warming. Rapid active re-warming is done in 104-108°F (40- 42°C) water for 15- 30 minutes as long as care can occur in an environment where there is no risk of refreezing. The temperature is important, as there is reduced effect with cooler temperatures and higher temperatures will cause burns. Passive re-warming or dry heating is not considered acceptable, but may be the only option depending on the operational environment and involves using body heat and blankets; always attempt to move the casualty safely to a warmer environment. Do not use blow dryers, space heaters, or the like as these will cause burns. The goal is complete thawing and maximum perfusion as evidenced by hyperemia, swelling, and pain.10 Rubbing the affected areas is to be avoided as this will further traumatize the skin. The re-warming process can be expected to be very painful and narcotic and non-steroidal medications, including Ibuprofen/Aspirin and/or Ketamine should be utilized liberally. It is tempting to re-warm slowly because this is better tolerated but tissue survival is improved with rapid re-warming. Pain usually subsides in approximately 3 days but prolonged aches, shooting pains, and throbbing can be expected for weeks.1 Early surgical consultation should be made. Rapid re-warming can be conducted at point of initial care, but early evacuation to definitive care should be considered at the earliest available time. It is also very important that when rapid re-warming is done, it is to be completed, as refreezing after partial thawing will result in more severe injury.

During the course of treatment, patients should be prohibited from using any tobacco and nicotine-containing products as well as any medications inducing vasoconstriction. The limb should be elevated to reduce swelling. After re-warming, electrolyte abnormalities and rhabdomyolysis can occur. Electrolytes should be monitored every 6 hours initially, until normalized. Scheduled ibuprofen (400 mg PO every 6 hours) should be considered, with narcotics utilized for refractory pain. Sympathectomy and vasodilators have been attempted in studies, but there is insufficient evidence that these modalities improve outcomes and should not be routinely attempted. If available, hyperbaric oxygen can be considered and started between day 5 and 10.4 Evidence for the use of systemic prophylactic antibiotics is lacking and is not recommended. Regular application of topical aloe vera may help limit tissue loss.4 After resolution of edema, whirlpool therapy combined with exercise can help maximize functional recovery of the extremity.

Photo documentation at point of injury when feasible can assist in continuum of care.

Thrombolytic Therapy

Care must be made to ensure patients are candidates for Tissue Plasminogen Activator (tPA) prior to therapy (see below). Patients should be within 24 hours of the start of injury. Patients should have evidence of severe frostbite as well as circulatory compromise as demonstrated by decreased or absent pulses, lengthened capillary refill, and/or ischemic discoloration of distal digits.11

Candidates for tPA:

- Within 24 hours of start of injury.
- Evidence of injury with vascular compromise.

Relative contraindications to tPA for frostbite injury include:

- Concurrent trauma.
- Recent surgery or hemorrhage.
- Bleeding diathesis.
- Cold contact injury without frostbite injury.
- Greater than 24 hours of ischemia.
- Evidence of freeze-thaw-freeze injury.

Patients that are being considered for therapy should be taken for diagnostic arteriogram of the affected extremity. If perfusion is compromised, papaverine, a vasodilator, may be introduced intraarterially at a rate of 30 mg/hr to decrease local vasospasm. Intraarterial tPA should be administered through the arterial catheter as follows: 2-4 mg bolus followed by a continuous infusion of 0.5-1.0 mg/h into the extremity. If multiple extremities are involved, arterial catheters are positioned in each extremity. The maximum dose of tPA would then be divided amongst the number of extremities. For example, if two extremities are involved, the maximum rate for each extremity is 0.5 mg/h. In addition, intraarterial heparin should be administered through the arterial sheath at a rate of 500 units/h to prevent new clot formation and extension of existing thrombi. Serial labs including PTT, fibrinogen, Hgb/Hct, and platelets are repeated every 6 hours. There is no PTT goal as the dose is small for a normal-sized adult. Angiograms are to be repeated every 8 to 12 hours to evaluate response to therapy. Termination of therapy is recommended to end with complete perfusion or at 48 hrs, unless complications from tPA occur or fibrinogen levels fall below 150. Patients should be closely monitored for hemorrhagic complication, neurologic, and cardiovascular complications from the tPA. If a patient develops serious bleeding complications, the tPA and heparin should be discontinued. If revascularization has occurred, and final cessation of tPA is made, heparin should be continued for at least 72 hours.11,12

A systemic, intravenous approach to tPA administration is available, but only with the ability to perform technetium scanning to confirm vascular compromise and response to therapy. The systemic approach is administration of a tPA bolus of 0.15 mg/kg intravenously followed by a 0.15 mg/kg/hr infusion over the next 6 hours to a maximum dose of 100 mg. After completion of tPA, heparin is started with a goal of two times normal control and is continued until conversion to Coumadin. Anticoagulation with Coumadin should be continued for 4 weeks.13

tPA should be avoided in a setting that lacks the ability to monitor and treat bleeding complications.

DEBRIDEMENT

Major surgical debridement, should not be performed in the operational environment for US Military or casualties that can be evacuated. Early excision is not part of the therapy for frostbite. Excision should be delayed until margins of injury are fully demarcated; this may take months. For minor injuries, local wound care can be performed with the addition of topical antibiotic and aloe vera gel or a sterile topical emollient every 6 hours. Wound care should be performed BID and sterile non-adherent dressing should be applied. Vesicles from second degree become dry, black, and hard in approximately 2 weeks and will generally peel away at 3-4 weeks.

Third degree frostbite forms an eschar and can be debrided in approximately 2-8 weeks depending on severity of the injury. There will be an ulcer and this will take further time to heal. The surrounding skin is easily traumatized from second degree frostbite.

With fourth degree frostbite, the mummification of the extremity or digit will become readily apparent in approximately 2 weeks. Most will continue the mummification process without sequelae and this should be a minimally painful process, but throbbing, shooting pains, and potentially severe aching can be expected for up to a month. Some moisture and purulence can be expected without significant concern unless signs of local or systemic sepsis present. The level of debridement/amputation can be delayed until mummification is complete.

For cases of full thickness injury (third and fourth degree) with infection, debridement and possible amputation are to be conducted expediently.

In general, surgical debridement should be done at a definitive care site outside of theater.

SUPPORTIVE CARE

Cold injury may have permanent symptoms after the injury. It is common to have patients with minimal injuries complain of persistent coldness, pain, and hyperhidrosis of the affected extremity. In addition, second degree frostbite will likely have intact, but easily damaged, skin. In many cases, patients are more susceptible to future cold injury which frequently is more severe than the initial insult.

Basic treatment for persistent side effects includes nonsteroidal analgesics and antiperspirants. These should be available at forward operating locations until further definitive dermatologic and surgical care can be provided.14

Mild injury can be managed at site of injury but any full thickness injury should be evacuated. Tetanus booster should be provided based on immunization history.