Cold weather injuries of the feet can be broken down into two basic categories; damp/cold and dry/cold. Damp/cold is a much more common foot injury. The reason water is so important in cold weather injuries is that it carries a higher clear-cut heat than air. This means that water may absorb much more heat, far greater than air. As a result, damp/cold injuries are a much more common and problematic injury. Most damp/cold injuries occur at or just below the freezing point and really do not require a big drop in the mercury. Damp/cold injuries go by many names including frostnip, immersion foot, trench foot, chilblains and pernio. Dry/cold injuries, what we usually call frostbite and hypothermia, require a much colder environment to cause damage to the foot.

Theres a number of ways that the body looses heat. Heat could be lost by conduction. Water is a nice conductor of heat. Heat is also lost by windy conditions (convection) and contacting a cooler surface (radiation) such as standing on snow. And forget all the old tales about peppermint schnapps. Alcohol, hunger, anemia and cardiovascular disease all build you more susceptible to heat loss and cold weather injury.

The cells that make up our bodies consist of 75-85% water. In cold weather injuries, damage occurs as the water in these cells begins to freeze. Freezing results in interruption of normal cell function and eventually ruptures of the cell by expansion. Some refer to this process as dehydration of the cell. Ultimately, blood flow is arrested and even shunted away from the threatened area. Heres a comparison of dry and damp cold weather injuries;

Dry Cold Injuries (frostbite)

Typically more superficial (2-3mm) tissue damage (skin, nails, superficial subcutaneous tissues) Tissue damage more severe and apparent Damaged cells will heal over time Local wound care is necessary following the injury Infection is common

Damp Cold Injuries (immersion foot)

Tissue damage usually deep (nerves, arteries subcutaneous tissue) Damaged cells may not heal and cause chronic pain, edema and blotchy discoloration of the skin Superficial wounds (gangrene) and infections are uncommon

Prevention measures, although also apparent, are often overlooked. Remember, 30% of heat loss is from the head. Its OK to wear a hat.

The initial symptoms of cold weather injuries of the foot are obvious but generally ignored. Symptoms include toes that are damp, pale cold and clammy. Swelling and maceration are common. Discomfort upon warming suggests tissue damage. After several days, bubbles and blisters may occur in cases of superficial damage. Superficial gangrene will appear over several days to a week depending upon the extent of tissue damage. Actual assessment of the damage caused by a thermal injury is commonly not possible until several days have lapsed following the injury.

Treatment of cold exposure and thermal injuries consists of gradual warming. Be sure to warm the feet slowly with luke warm water at approximately 104-106 F. Re-warming does not take long and may generally be completed in less than 30 minutes. In severe cases, care of soft tissue gangrene and infection should be managed by your doctor. Wound care may add antibiotics, anticoagulants or other medications to reverse platelet aggregation and decrease blood viscosity. Hyperbaric oxygen and sympathetic nerve blocks are also employed to aid in wound healing. Pain management is also essential. Most surgeons will defer treatment of frostbite for several years to offer mother nature a chance to heal the majority of the injury. There is no known treatment for the long term pain following damp/cold tissue injuries.

Treatment Tips

Caution; feet that have sustained a thermal injury are unable to sense the temperature of the warm water and are therefore susceptible to burns. If you become caught outside with a cold weather injury to of the foot, wait to warm the foot until you might rest in one spot. Warming the foot and then walking distances will cause more pain and tissue damage. Delay surgical care until the wound has become well demarcated. This can mean several weeks to decades following the injury.

Button up, its cold out there.