Prevention and Treatment of Frostbite

No evidence supports applying a dressing to a frostbitten part intended to remain frozen until rewarming can safely be achieved. If this is considered, it should only be done if practical and will not interfere with mobility. Bulky, clean, and dry gauze or sterile cotton dressings should be applied to the frozen part and between the toes and fingers. ( 2 – Weak , C)

If at all possible, a frozen extremity should not be used for walking, climbing, or other maneuvers until definitive care is reached. If use of the frozen extremity for mobility is considered, a risk-benefit analysis must consider the potential for further trauma and possible poorer outcome. Although it is reasonable to walk on a foot with frostbitten toes for evacuation purposes, it is inadvisable to walk on an entirely frostbitten foot because of the potential for resulting morbidity. This risk is theoretical and based on the panel’s opinion. Mills described frostbite patients who ambulated on frozen extremities for days and sustained no or limited amputation. If using a frozen extremity for locomotion or evacuation is unavoidable, the extremity should be padded, splinted, and kept as immobile as possible to minimize additional trauma. ( 2 – Weak , C)

Field rewarming by warm water bath immersion can and should be performed if the proper resources are available and definitive care is more than 2 h distant. Other heat sources (eg, fire, space heater, oven, heated rocks) should be avoided because of the risk of thermal burn injury. Rapid rewarming by water bath has been found to result in better outcomes than slow rewarming. Field rewarming should only be undertaken if the frozen part can be kept thawed and warm until the victim arrives at definitive care. Water should be heated to 37 to 39°C (98.6 to 102.2°F), using a thermometer to maintain this range. If a thermometer is not available, a safe water temperature can be determined by placing a caregiver’s uninjured hand in the water for at least 30 s to confirm that the water temperature is tolerable and will not cause burn injury. Circulation of water around the frozen tissue will help maintain correct temperature. Because the water may cool quickly after the rewarming process is started, the water should be continuously and carefully warmed to the target temperature. If the frozen part is being rewarmed in a pot, skin should not press against the bottom or sides. Rewarming is complete when the involved part takes on a red or purple appearance and becomes soft and pliable to the touch. This is usually accomplished in approximately 30 min, but the time is variable depending on the extent and depth of injury. The affected tissues should be allowed to air dry or be gently dried with a blotting technique (not rubbing) to minimize further damage. Under appropriate circumstances, this method of field rewarming is the first definitive step in frostbite treatment. (1 – Strong, B)

Most injuries do not become infected, but adding an antiseptic solution (eg, povidone-iodine, chlorhexidine) to the rewarming water has theoretical benefits of reducing skin bacteria. Evidence for this practice does not exist for frostbite care, however. Adding an antiseptic solution to the water while rewarming is unlikely to be harmful and might reduce the risk for cellulitis if severe edema is present in the affected extremity. (2 – Weak, C)

During rewarming, pain medication (eg, NSAIDs or an opiate analgesic) should be given to control symptoms as dictated by individual patient situation. (1 – Strong, C)

According to the foregoing guidelines, rapid rewarming is strongly recommended. If field rewarming is not possible, spontaneous or slow thawing should be allowed. Slow rewarming is accomplished by moving to a warmer location (eg, tent or hut) and warming with adjacent body heat from the patient or a caregiver, as previously described. The expert panel agrees that slow thawing is a reasonable course of action to initiate the rewarming process if it is the only means available. (1 – Strong, C)

Debridement of blisters should not be routinely performed in the field. If a clear, fluid-filled blister is tense and at high risk for rupture during evacuation, blister aspiration and application of a dry gauze dressing should be performed in the field to minimize infection risk. Hemorrhagic bullae should not be aspirated or debrided in the field. These recommendations are common practice but lack evidence beyond case series. ( 2 – Weak , C)

Aloe vera ointment has been shown in an observational study and an animal model to improve frostbite outcome by reducing prostaglandin and thromboxane formation. Topical agents do not penetrate far into tissues, however, so aloe vera is theoretically only beneficial for superficially injured areas. The study supporting the benefit of aloe vera examined its application on unroofed blebs where it would be able to penetrate underlying tissue. Topical aloe vera should be applied to thawed tissue before application of dressings. ( 2 – Weak , C)

Bulky, dry gauze dressings should be applied to the thawed parts for protection and wound care. Substantial edema should be anticipated, so circumferential dressings should be wrapped loosely to allow for swelling without placing pressure on the underlying tissue. ( 1 – Strong , C)

A risk-benefit analysis must consider the potential for further trauma and, ultimately, potentially higher morbidity if a thawed part is used for ambulation. For example, it might be reasonable to walk on a foot with thawed toes for evacuation purposes, but it is inadvisable to walk on a recently thawed frostbitten foot because of the potential resulting morbidity. Very little evidence is available to guide recommendations. In one study, mobilization within 72 h after thawing did not affect tissue loss, complications, or hospital length of stay. After the rewarming process, swelling should be anticipated. If passive thawing has occurred, boots (or inner boots) may need to be worn continuously to compress swelling. Boots that were removed for active rewarming may not be able to be re-donned if tissue swelling has occurred during the warming process. The panel’s clinical experience supports the concept that a recently thawed extremity should ideally not be used for walking, climbing, or other maneuvers and should be protected to prevent further trauma. (2 – Weak, C)

If possible, the thawed extremity should be elevated above the level of the heart, which might decrease formation of dependent edema. (1 – Strong, C)

Recovery of thawed tissue partly depends on the level of tissue oxygenation in the postfreezing period. One small study that measured hand temperature at normobaric hypoxia found decreased skin temperatures with decreasing F_IO₂. However, hyperoxia has been found to cause vasoconstriction in the extremities; therefore, oxygen should not be applied routinely to patients who are not hypoxic. Although evidence is lacking to support use of supplemental oxygen for frostbite, oxygen may be delivered by face mask or nasal cannula if the patient is hypoxic (oxygen saturation <88%) or at high altitude above 4000 m. (2 – Weak, C)

Similar recommendations apply to hospital or field clinic treatment of hypothermia before frostbite treatment (see previous). (1 – Strong, C)

Similar recommendations apply in the hospital or field clinic regarding hydration (see previous). ( 1 – Strong , C)

Similar recommendations apply in the hospital or field clinic regarding LMWD (see previous). ( 2 – Weak , C)

Frozen tissue should be assessed to determine whether spontaneous thawing has occurred. If tissue is completely thawed, further rewarming will not be beneficial. Rapid rewarming should be undertaken according to the field protocol described previously if the tissue remains partially or completely frozen. (1 – Strong, B)

Clear or cloudy blisters contain prostaglandins and thromboxanes that may damage underlying tissue. Hemorrhagic blisters are thought to signify deeper tissue damage extending into the dermal vascular plexus. Common practice is to drain clear blisters (eg, by needle aspiration) while leaving hemorrhagic blisters intact. Although this approach to frostbite blister management is recommended by many authorities, comparative studies have not been performed and data are insufficient to make absolute recommendations. Some authors argue that unroofing blisters might lead to the desiccation of exposed tissue and that blisters should only be removed if they are tense, likely to break or be infected, or interfere with the patient’s range of motion. In a remote field situation, draining or unroofing blisters may not be under control of the provider. Blisters most often will have been broken by the patient’s boots. In this case, the most important treatment is applying aloe vera and a sterile dressing to the unroofed blister. Debridement or aspiration of clear, cloudy, or tense blisters is at the provider’s discretion, with consideration of patient circumstances, until better evidence becomes available. (2 – Weak, C)

Topical aloe vera cream or gel should be applied to the thawed tissue before application of dressings. Aloe vera is reapplied at each dressing change or every 6 h. (2 – Weak, C)

Frostbite is not an inherently infection-prone injury. Therefore, antibiotic administration specifically for preventing infection during or after frostbite injury is not supported by evidence. Some authorities reserve antibiotics for situations when edema occurs after thawing because of the notion that edema increases skin susceptibility to infection by gram-positive bacteria. However, this practice is not based on evidence. Systemic antibiotics, either oral or parenteral, should be administered to patients with significant trauma, other potential infectious sources, or signs and symptoms of cellulitis or sepsis. (1 – Strong, C)

Tetanus prophylaxis should be administered according to standard guidelines. (1 – Strong, C)

If NSAIDs have not been initiated in the field, ibuprofen should be administered at a dose of 12 mg·kg^-1 divided twice daily (to inhibit harmful prostaglandins but remain less injurious to the gastrointestinal system) until the frostbite wound is healed or surgical management occurs (typically for 4 to 6 wk). (2 – Weak, C)

The goal of thrombolytic therapy in frostbite injury is to lyse and clear microvascular thromboses. For deep frostbite injury with potential significant morbidity, angiography and use of either IV or intra-arterial tissue plasminogen activator (tPA) within 24 h of thawing may salvage some or all tissue at risk. A retrospective, single-center review by Bruen et al. demonstrated reduction in digital amputation rates from 41% in those patients who did not receive tPA to 10% in patients receiving tPA within 24 h of injury. The 20-y series presented by the Regions Hospital group found that two-thirds of patients who received intra-arterial tPA responded well and that amputation rate correlated closely with angiographic findings. The Massachusetts General Hospital group has proposed a screening and treatment tool for thrombolytic management of frostbite based on a case report and their evaluation of the Utah and Minneapolis experiences. Twomey et al from Hennepin County Medical Center have developed a specific protocol based on a small group of good outcomes with intravenous tPA. Further study is needed to compare intra-arterial vs IV tPA on tissue salvage and functional outcome. Animal studies demonstrate benefit from thrombolytics.When considering using a thrombolytic, a risk-benefit analysis should be performed. Only deep injuries with potential for significant morbidity (eg, extending into the proximal interphalangeal joints of digits) should be considered for thrombolytic therapy. Potential risks of tPA include systemic and catheter site bleeding, compartment syndrome, and failure to salvage tissue. The long-term, functional consequences of digit salvage using tPA have not been fully evaluated.
Thrombolytic treatment should be undertaken in a facility familiar with the technique and with intensive care monitoring capabilities. If a frostbite patient is being cared for in a remote area, transfer to a facility with tPA administration and monitoring capabilities should be considered if tPA can be started within 24 h of tissue thawing. Time to thrombolysis appears to be very important, with best outcomes within 12 h and ideally as soon as possible. Recent work from Hennepin County has found that each hour of delay of thrombolytic therapy results in a 28% decrease in salvage. Rare use of tPA in the field has shown variable success and should only be undertaken with extreme caution because bleeding complications may be impossible to detect and treat. If other treatment options are limited or unavailable, tPA should be considered for field treatment only of severe frostbite extending to the proximal interphalangeal joint or more proximally (eg, Cauchy classification grade 3 to 5).

Method of administration

Dosing is typically a 3 mg bolus (30 mL of 0.1 mg·mL^-1 solution) followed by infusion of 1 mg·mL^-1 (10 mL·h^-1) until specialists (eg, vascular, burn, radiology) recommend discontinuation. Heparin is administered concurrently: 500 units·h^-1.Intra-arterial angiography or IV pyrophosphate scanning should be used to evaluate the initial injury and monitor progress after tPA administration as directed by local protocol and resources. As of the end of 2018, the following have been published on tPA use in frostbite: 1 randomized controlled prospective trial (tPA plus iloprost, 16 patients), 3 retrospective cohort studies (59 patients), 8 retrospective case series (130 patients), and 3 case reports. Although further studies are needed to determine the absolute efficacy of tPA for frostbite injury and to compare intra-arterial tPA to IV prostacyclin, we recommend IV or intra-arterial tPA within 24 h of injury as a reasonable choice in an environment with appropriate monitoring capabilities.

(1 – Strong, C)

In patients with delayed presentation (4-24 h from the time of the frostbite thawing), noninvasive imaging with technetium pyrophosphate or magnetic resonance angiography can be used at an early stage to predict the likely levels of tissue viability for amputation. Cauchy et al. described the combination of a clinical scoring system and technetium scanning to successfully predict subsequent level of amputation on day 2 after frostbite rewarming. Single photon emission computed tomography (CT)/CT combines the anatomic precision of CT with the functional vascular information obtained from multiphase bone scintigraphy. Kraft et al used single photon emission CT/CT for 7 patients with frostbite and found it improved surgical planning for deep frostbite injuries by enabling early and precise anatomic localization of nonviable tissues. If available, appropriate imaging should be used to assess tissue viability and guide timing and extent of amputation.
If available, appropriate imaging should be used to assess tissue viability and guide timing and extent of amputation. (1 – Strong, C)

Iloprost, a prostacyclin (PGI2) analogue, is a potent vasodilator that also inhibits platelet aggregation, down-regulates lymphocyte adhesion to endothelial cells, and may have fibrinolytic activity. Intravenous iloprost was first used for treatment of frostbite by Groechenig in 1994, in 5 patients with second- and third-degree frostbite. He infused iloprost daily, starting at 0.5 ng·kg^-1 and increasing to 2.0 ng·kg^-1 total dose over 3 d, and then continued for between 14 and 42 d. Recovery without amputation was achieved in all patients.
A randomized trial by Cauchy et al assessed the efficacy of aspirin plus: 1) buflomedil, an alpha-blocker vasodilator; 2) iloprost; or 3) intravenous tPA plus iloprost. Forty-seven patients with severe frostbite, with 407 digits at risk, were randomly assigned to 8 d of treatment with the 3 different regimens. Iloprost alone (0% amputation rate) was found superior to tPA plus iloprost (19%) and buflomedil (60%) groups. A limitation of this study was that ischemia was not documented with angiography or technetium scanning before treatment; groups were randomized according to clinical severity.
A Canadian study documented full recovery of grade 3 frostbite when iloprost was started within 48 h of injury in 2 long distance runners. In a Finnish study, iloprost was partially beneficial with digit salvage rate of 78% in 4 persons: 2 with contraindication for tPA, 1 with failed tPA therapy, and 1 with vasospasm without thrombosis on angiography. One patient with minimal response to tPA had complete reperfusion with iloprost.
Despite the limitations of these initial studies, iloprost has shown consistently favorable effects. Extending the treatment window, Pandey et al. reported good results with iloprost therapy up to 72 h after injury. In 5 Himalayan climbers with 34 digits at risk, 5 d of daily iloprost infusion produced excellent outcomes in 4 of 5 patients. Treatment delayed beyond 72 h has not been beneficial except in 1 patient. No serious side effects have been noted in these studies.
Intravenous iloprost should be considered first-line therapy for grade 3 and 4 frostbite <72 h after injury, when tPA is contraindicated, and in austere environments where tPA infusion is considered risky or evacuation to a treatment facility will be delayed. Field use of both iloprost and IV tPA has been advocated to reduce delay in treatment for mountaineers who will invariably take >48 h for evacuation to a hospital. In these situations, iloprost may be the safer alternative. The IV form of iloprost is not approved by the US Food and Drug Administration, however. Consider iloprost for deep frostbite to or proximal to the proximal interphalangeal joint; within 48 h after injury, especially if angiography is not available; or with contraindications to thrombolysis. Expedition physicians should consider adding iloprost to their medical armamentarium, especially if it can be safely sourced and when treatment is occurring outside of the United States. (1 – Strong, B)

No evidence supports use of low molecular weight heparin or unfractionated heparin for initial management of frostbite in the field or hospital, although climbers and practitioners in many regions use these medications. Evidence supports use of heparin as adjunctive therapy in tPA protocols, as described previously. Heparin has been used in conjunction with iloprost as well; the 5 patients in the 1994 Groechenig iloprost study,
the 1 Israeli traveler with excellent outcome in the Kathmandu study, and 4 patients in the Finnish study were treated with low molecular weight heparin (enoxaparin) in addition to iloprost. Whether low molecular weight heparin offers additional benefit when combined with iloprost requires further investigation; currently data are insufficient for a recommendation on this combination. (, U)

Certain vasodilators have the potential to improve outcomes and can be used with minimal risk. However, as discussed earlier, data demonstrating benefit are limited. Iloprost is the only vasodilator with reasonable scientific evidence supporting its use. (, U)