Non-Freezing Cold Injury - The Basics
Non-Freezing Cold Injury (or “NFCI” for short) has several names—“immersion foot,” and “trench foot,” the term coined to describe the ailment which caused over 29,000 British casualties in Word War I, are just two. Though perhaps not as familiar as the “freezing” injuries like frostbite, NFCI is quite serious and can potentially lead to permanent nerve and muscle damage. In extreme cases, tissue damage may be sufficiently severe to require even amputation. Essentially, NFCI is a localized injury to the body’s lower extremities—like the legs and feet—caused by prolonged exposure to wet and cold conditions just above freezing temperatures (typically between 32° to 55° Fahrenheit).
Medically speaking, NFCI is the result of microvascular endothelial damage, stasis and vascular occlusion. In simpler terms, this means that the feet are exposed, via soggy or sweaty socks, to moisture and cold for a prolonged period of time. When improperly protected from the elements, the human body naturally loses heat. In response, the body’s blood vessels constrict, which reduces blood flow to extremities like the toes and feet. As a consequence, cells in the toes and feet are deprived of essential oxygen and nutrients carried in the bloodstream. If feet are not properly warmed and dried after an extended period of time, the oxygen deprivation can cause nerve damage.
It is generally thought that NFCI tends to occur after about one to three days of exposure, though avid outdoorsmen attest that these injuries may develop much more rapidly, depending on the individual and the weather conditions. Indeed, there are documented cases of NFCI which occurred after grueling three hour hikes in wet conditions.
Signs and Symptoms
In a textbook NFCI case, the result is cold, swollen and numb feet—patients have described the sensation as a foot which feels “wooden.” The feet may appear mottled or even somewhat shiny or waxy. Both capillary refill time and tactile sensitivity can be measurably reduced. In some cases, though, symptoms may be less obvious at the onset—swelling may be mild, and rather than appearing mottled, the injured skin may simply be pale, cool, itchy, or tingly. Pain may also not fully develop until several days after exposure. When the feet and toes are warmed, the skin typically becomes warm, dry and red, or again itchy and tingly. The injured area may also exhibit marked sensitivity to cold—sometimes permanently. Blisters, ulcers and gangrene may develop and the recovery period may last weeks. Some patients simply experience sore and achy feet; some are completely unable to walk or to even wear shoes. In some cases, patients endure months of pain and disability. In the short term, patients should avoid walking on injured feet. Elevating the feet helps to reduce swelling and ibuprofen is recommended for inflammation.
Like most injuries, the best way to treat NFCI is simply to prevent its occurrence. The most important step is to keep feet warm and dry. As it is possible to develop NFCI in just a single day’s hike in wet socks, socks certainly play a crucial role and should be kept as dry as possible. Hikers recommend changing moist socks and airing out the feet systematically, and suggest drying wet pairs against the skin (inside the shirt while hiking, or draped across the chest or belly while sleeping) or by hanging them in the sun or over a campfire. Feet should also be kept warm and dry while sleeping, as just one night in cold, wet socks also can cause NFCI. Even minor symptoms should be taken seriously, as the effects of NFCI can linger for years after the initial injury.
Wearing Drymax socks may also be a big help in preventing NFCI, since they are able to keep feet far drier than any other socks!