Outdoor recreation in the winter, including backcountry skiing, cross-country skiing, snowshoeing, and mountaineering, can be rewarding and enjoyable, as long as precautions are taken to mitigate risks. Freezing cold injuries, such as frostnip and frostbite, can quickly turn an adventure from a fun time into a serious incident. These types of injuries occur when heat loss in tissues exceeds the body’s ability to adequately perfuse them and prevent freezing (blood flow = heat). In cold temperatures, blood is shunted to vital organs in the core and away from the extremities, thus increasing the chance of a freezing injury.
Prevention is always better than treatment. Prior planning and frequent assessments are key to frostnip and frostbite prevention.
Frostnip is the precursor to superficial frostbite. Prior to warming, skin is cold, numb, and can have the appearance of frost on the surface. After warming, skin becomes red. With quick action, frostnip is easily reversible and results in no tissue damage.
Superficial and Partial Thickness Frostbite
If frostnip is not treated, freezing begins to occur in subsequent layers of tissue, and more permanent damage is possible. Signs of superficial frostbite include pale, “waxy,” skin, numbness, and tingling. The tissue may have no sensation and will feel cold to the touch. After rewarming, tissue will swell and become painful. In the case of partial thickness frostbite, clear, fluid-filled blisters appear.
Deep frostbite affects all layers of skin, and in severe cases can cause damage to muscle and bone. When frozen, tissue can appear frosted, and is stiff to the touch and does not have sensation. Once rewarmed, deep frostbite is characterized by hemorrhagic blisters or necrotic (black) skin. It can take weeks to months before demarcation of damaged tissue is complete, which often results in amputation. Before rewarming, it is difficult to differentiate between superficial and deep frostbite.
Frostnip – Rewarm the affected tissue by covering exposed skin (e.g., putting on gloves, covering your face clothing or a scarf), direct contact (e.g putting cold hands in your armpits), and finding shelter/limiting exposure to the elements.
Frostbite - If there’s a possibility of refreezing, or if evacuation necessitates a walk-out, it’s better to keep the body part(s) frozen than to rewarm them. Refreezing substantially increases the risk of permanent damage and defrosted appendages are often swollen, blistered, and painful. However, tissues should not be intentionally kept frozen (i.e., the affected area should not be packed in snow) as it can result in further damage. If there is no chance of re-freezing, there are two rewarming options:
Rapid rewarming (preferred) - Rewarm the tissue in a water bath kept consistently between 98.6 and 102.2°F (bathtub temperature). Circulating water helps to keep tissues at the correct temperature. Rewarming time depends on the extent of the freezing, but is complete when tissues are re-perfused and soft/pliable. After rewarming, dry the affected tissue with gentle blotting or let it air dry. Keep blisters intact, and if they drain spontaneously, provide basic wound care.
Passive rewarming – While not as ideal, passive rewarming options can also be effective. These methods include moving to a warmer environment (sleeping bag, cabin, sitting next to a stove), or using body heat (placing affected tissue against someone else’s abdomen, or placing hands in your own armpits).
Any individual who experiences a frostbite injury that cannot be rewarmed should be evacuated immediately. If the tissue is rewarmed, provide wound care and evacuate in a timely manner.