September 24, 2010
The cold, hard, truth...
Unlike many in Hollywood and Washington DC who pretend to have PhD's in environmental science, we admit that what we know to be a fact about global warming can be written on the head of a pin with a jackhammer. But we are darn sure it has been cold these past few weeks and that it will get colder before it gets warmer again. So we thought now was a good time to discuss a specific type of injury that can occur when exposed to freezing temperatures. Cold injury runs the gamut from inconvenient to life threatening. Prevention is obviously best and early intervention and treatment is essential to prevent these potentials from becoming reality.
There are three general types of cold injury: Chilblain, Immersion foot (trench foot) and frostbite. Only frostbite involves the actual freezing of tissues as part of actual injury. As you would expect certain co-existing conditions make someone more or less susceptible to cold injury. Also because these injuries pre-date modern medicine, there are myths about treatment that are quite harmful indeed.
Chilblain is cold injury that falls into the irritating rather than the threatening category. It is characterized by red, scattered areas of itching and burning skin, mostly on the back of the hands and feet. This injury is seen almost exclusively in those folks with vascular disorders such as Raynaud's syndrome and other "collagen" diseases. These lesions tend to appear as the weather changes to cold and go away with the spring. There is no treatment per se, except maybe moving to warmer climates.
The very politics of the world we live in has been shaped to a greater or lesser extent by the cold injury known as trench-foot, or less colorfully as immersion foot. This condition has been following the footsteps of the military since before recorded history, but impacts the hunter and hiker as well. What happens with immersion foot is that the body reacts to cold feet in a manner devised to preserve the central warmth of the chest and central nervous system. It does so by shunting blood away from the heat draining feet.
Now this injury requires time to occur and is not a consequence of a few hours of cold feet in the tree stand or waterfowling. Wet or damp feet assist in the development of this injury by making it easier for your feet to lose their precious heat even when exposed to temperatures not far below 50 F (10 C). A period of 10 - 12 hours will usually be sufficient to induce immersion foot in the right conditions. If your toes are toasty, then regardless of outside temperatures, you can't suffer this illness. Layered socks, insulated, waterproof boots that allow for circulation and moisture wicking materials are safe guards here. Cigarettes, alcohol, and conditions that pre-dispose to reduced blood flow are risk factors for trench-foot.
Immersion injury goes through three phases: First as a natural response to hours of cold exposure the body begins to shut down blood flow to the feet. Clinically the feet become swollen, blue (sometimes white) and sensation is diminished. Actual pulses are difficult to detect in the affected lower extremity and naturally the foot feels cold. This lack of blood flow causes damage to nerves, small blood vessels and other tissues if prolonged. When re-warming does occur, the body over compensates the blood starved tissue and the extremity is very painful, hot, dry and red.
This phase can last several days. If the cold exposure was long enough, the tissue doesn't revive and ulcers and gangrene can set in leading to permanent disability and even amputation. Recovery (the last phase) is characterized by a normalization of vascular responses in the foot though there may be permanent skin changes. Excessive sensitivity to the cold may persist for years and tissue damage from more severe cases can result in debilitating nerve damage and resultant pain.
True frostbite results from the actual freezing of the tissues of the body. Feet, hands, ears and nose are the most commonly affected areas of the body. Historically frostbite has gone through several classifications to enhance specific treatment approaches. One such approach is to parallel burn injury with first degree, second degree etc. We feel it is more useful to talk about this serious condition in terms of frostnip, superficial and deep frostbite as the outcomes are very different. The colder the temperature the quicker these conditions can develop. In the Artic, even very brief unprotected exposure to the environment can result in a frostbite injury.
Frostnip is the mildest form of this class of cold injury and does not involve actual tissue freezing. Almost frozen is the best way to think about this complication and therefore the outcomes of treatment are always good. Affected tissues blanch white with a lack of blood flow and sensation is lost. Treatment is common sense: get out of the cold. Tissues quickly re-establish normal blood flow, tingling occurs as nerves "wake up" and resolution is quick and complete.
Superficial frostbite is much more serious and is the result of actually freezing your living flesh. By definition it involves the skin and subcutaneous tissues. There are several technical theories as to the exact cellular injury mechanism, suffice to say having a frozen body part is a bad thing. The frozen tissue is hard and has a waxy white coloration. There is a residual softness to the underlying (non-frozen) tissues, but no sensation or blood flow to the frozen part. Think a pack of burgers in the freezer for an hour or so. The outside is crusted hard frozen, but underneath is still pliable.
The frozen body part is totally without sensation. How much tissue "revives" depends on duration and extent of the injury. It is essential that once you begin to thaw your frostbitten part, you do not allow for re-freezing. For example it's better to walk on a frozen foot for two days than to thaw at night only to have it re-freeze the next day as you are seeking help. This may sound counter intuitive, but is based on extensive observation.
Treatment is literally defrosting your body part. Over zealous exposure to campfire warmth is absolutely not the way to do this. Remember, the affected part won't feel anything and you are most likely to add burn injury to your cold injury! Rubbing snow on the area is a hold over from Napoleon's army and is as useful as most medical approaches from the early 1800's.
Field treatment is not a good idea and is to be discouraged. Focus entirely on getting to medical attention. The frozen area can not tolerate re-freezing without much more serious injury. Please remember de-frosting is going to hurt a lot and the formerly frozen tissues are going to require very specific medical attention. Just for completeness sake, frozen body parts are often accompanied by overall low body temperature (hypothermia), and dehydration, hence the absolute need for formal medical attention.
Re-warming (de-frosting) is best done in a warm water bath with temperatures held constant at around 104 F (40 C). Substantial pain is to be expected during a prolonged healing process. Once de-frosted, the affected
area becomes red and swollen as well as discolored. Large blisters develop at the depth of injury and are to be left alone to re-absorb (photo #1) over the next week or so.
Fingers or toes must be kept separate with sterile bandages (photo #2). A thick, hard, black covering (eschar) develops and healing is from the inside out. This eschar may take a month or so to separate from the healed new tissue beneath. Increased sensitivity to heat and cold can persist for a very long time. Amputation is uncommon and with appropriate treatment that avoids infection and re-freezing, recovery is nearly complete.
Deep frostbite is another story altogether. Think bone-in roast that has been in your freezer for a week. With this situation not only is the skin and subcutaneous tissue frozen, but nerves, large blood vessels, tendons and bones are frozen. This results in a hard, solid and wood like texture. Tissue will be lost either to spontaneous amputation (falling off) during healing or via surgical intervention.
Treatment involves attending the likely co-morbid medical issues and the painful de-frosting procedure. Tissues with deep frostbite do not revive and remain cold, and with a bluish or gray coloration. Blisters eventually develop at the juncture of living and dead tissue. Healing is slow, painful and incomplete with residual and permanent tissue loss.
Needless to say, cold injury is entirely preventable. If you are planning a wilderness trip into the cold, or even a trip in the truck during severe cold weather conditions, prepare for the unexpected. Carry a satellite phone or a homing beacon in case of emergency, more locally a well-charged cell phone. Pack to spend the night even if that is not in the original plan and always have fire-starting tools with you. Extra blankets in the auto are essential this time of year.
As always, be safe, enjoy the outdoors and feel free to contact us anytime via our website www.thehuntdoctors.com