Frostnip is distinct from frostbite in that it is associated with intense vasoconstriction, no intra-or extracellular ice crystals, and no tissue destruction. Frostbite is classified into four degrees of injury based on physical findings and imaging after rewarming (see Table 2) 1,2. However, in the field a two tier classification scheme is preferred to simplify. Certain preventative strategies are recommended: maintain body hydration, minimize medications or diseases the decrease perfusion, cover all skin and scalp to avoid vasoconstriction, minimize tight clothing which constricts blood flow, maintain adequate nutrition and use oxygen if in hypoxic conditions. Exercise is protective up to the point that exhaustion causes collapse and subsequent rapid heat loss. Hand or foot warmers are highly recommended to maintain peripheral warmth, and if frost bite is suspected the extremity should be warmed by placement in the axilla or on the abdomen 2.
Table 2. Classification Schemes of Frostbite
1st Degree Numbness, erythema; slight epidermal sloughing
2nd Degree Superficial skin vesiculation, blisters with clear/milky fluid, erythema, edema
3rd Degree Deeper, hemorrhagic blisters; injury beyond dermal vascular plexus
4th Degree Injury completely through dermis, involves subcutaneous tissue, necrosis to level of bone
*Superficial Minimal anticipated tissue loss (1st – 2nd degree)
*Deep Deeper injury, anticipated loss (3rd-4th degree)
*Two tier classification scheme
Once a digit or extremity is deemed frozen, all jewelry should be removed. Now, to thaw or not to thaw? If there is a possibility that the digit is going to refreeze, then it is much safer to keep it frozen until it can be thawed indefinitely. Do not purposefully keep the digit at below freezing temperatures, and allow spontaneously thawing if possible, but avoid refreezing at all costs. Fluids should be administered if possible, given orally unless the patient has nausea with vomiting or AMS. If possible, warm any oral or IV fluid before infusion or intake. Low molecular weight dextran can also be given to decrease blood viscosity and improve perfusion 2. Pain management should also be started, with ibuprofen preferred over aspirin. Start the patient on 12mg/kg/day divided into two doses to a max of 2400 mg/d divided into four doses 2,3. No evidence supports placing a dressing over the affected digit or extremity if it is to remain frozen, but the affected part should not be used (climbing, walking (with the exception of a single frostbitten toe), etc.). If you must use the extremity, pad or splint it to minimize movement and additional trauma 2.
If definitive care is over two hours away, rapid rewarming in a water bath at about normal body temperature is advised 4. Again, this should be done only if the frozen part can be kept thawed. A good endpoint to the rewarming is when the digit turns purple or red and is soft to the touch. Allow it to air dry or gently blot-dry it with a towel. Blisters should not be debrided, but can be aspirated and covered, with the exception of hemorrhagic bullae which should not be aspirated or debrided. Loose, dry dressing can be applied to thawed parts, anticipating probable edema which can be lessened by elevating the extremity above the heart. Aloe vera has theoretical benefits and should be applied to thawed tissue before dressing 3.
Once at a hospital, treatment can mirror field treatment with regards to hydration, low molecular weight dextran, rapid rewarming of tissues (if still partially or completely frozen), aloe vera and blister management. Systemic antibiotics should only be administered if there is significant trauma or another source of infection, but tetanus prophylaxis is recommended. Low dose ibuprofen (6 mg/kg twice a day) should be continued 4-6 weeks or until the wound is healed. Use of thrombolytics (IV or intraarterial tissue plasminogen activator (tPA)) should only be used if there is a risk of significant morbidity to the limb, and should be given within 24 hours. It should never be used in the field since bleeding complications cannot be monitored. The prostacyclin analog iloprost has been shown to reduce amputation rate and should be a first line agent if available. Imaging including magnetic resonance imaging or technetium pyrophosphate can be used to determine viability of the tissues and predict the need for amputation. The limb should be monitored for signs of compartment syndrome, and unless infection occurs, and amputation should be delayed for 1-3 months until definitive demarcation 2.
1. Cauchy E, Chetaille E, Marchand V, Marsigny B. Retrospective study of 70 cases of severe frostbite lesions: a proposed new classification scheme. Wilderness & environmental medicine 2001;12:248-55.
2. McIntosh SE, Opacic M, Freer L, et al. Wilderness Medical Society practice guidelines for the prevention and treatment of frostbite: 2014 update. Wilderness & environmental medicine 2014;25:S43-54.
3. Heggers JP, Phillips LG, McCauley RL, Robson MC. Frostbite: experimental and clinical evaluations of treatment. Journal of Wilderness Medicine 1990;1:27-32.
4. Malhotra MS, Mathew L. Effect of rewarming at various water bath temperatures in experimental frostbite. Aviation, space, and environmental medicine 1978;49:874.