Perspectives in Circulation Today

Cold Damage, Hypothermia, Exposure and Frost Bite

Mottled Painful Feet on Presentation

This 50 year old alcoholic male smoker was referred by his vascular surgeon from a nearby hospital when standard therapies there appeared not to benefit him or relieve his pain. His 2-pack/day smoking habit, his case of beer/day habit and a stuporous sleep with an undocumented amount of exposure over a few days were associated with findings of dehydration and polycythemia and blue swollen feet on admission to his local hospital. A there venogram revealed multiple thrombi in his calves. Nonspecific RST changes on his cardiogram and multiple premature beats were thought to be compatible with an alcoholic myocardiopathy. He was treated with heparin, bedrest and subsequently coumadin with a decrease in the swelling of his feet over several days but pain and the changes shown in our baseline photograph persisted. At the time of his transfer to the Bryn Mawr Hospital, his mobility was limited to bedrest and a wheelchair.

Skin Growing under Necrotic Toe Tips

Baseline Doppler studies of his arteries were essentially normal to the midfeet; distally the feet were pulseless. He was treated first with foot soaks containing microfiltered sea water and Betadine. The feet were then pumped in the Miniboot with his feet immersed in isotonic diluted sea water (Sea Soaks TM) containing gentamicin. The soles of his feet improved within the first few days. The necrotic areas of his toes firmed up and then separated as skin grew beneath them. Strong Doppler waveforms were eventually documented in all of his toes. He did well.

Healed, Ambulatory and Pain-free

Comments:The usual therapies for thromboembolism had failed to clear the thrombi from the feet of this man. His toes appeared to be mummifying and his pain had been unrelieved. Such feet are extremely painful, especially in nondiabetics with normal sensation. They may find therapy with their legs extended horizontally in our Long Boots to be painful. They are usually quite comfortable during Miniboot therapy which is accomplished in the sitting position. If they do have pain, it is usually lessened by pumping them with their feet immersed in our Sea Soaks solution. How else might this man's feet have been salvaged? His referring physicians had given his feet up for lost. How did his illness come about? While his health habits were poor, he had no peripheral vascular complaints until awakening from his episode of stupor. Exposure as discussed below most likely played a major role.

Discussion: A soldier is pinned down in a rice paddie with a water temperature of 89 degrees F. The water being a good conductor of heat, he becomes hypothermic and protecting his body core temperature as best he can, he ceases to perfuse his legs. Many hours later he is found close to death with two gangenous feet. A college track athlete finds he returns to his dorm wet with sweat after his evening run along snow-covered roads. He learns he can comfortably run the last half mile wearing nothing but his bathing suit and sneakers if he runs the first two miles wearing his sweat suits and parka to become overheated. Surprising results may be noted depending on wind, water, activity, ambient temperature, time of exposure and particular surface exposed. Historically, nonfreezing injuries have been described: Chilblains (perniones), immersion foot and trenchfoot. Freezing injuries have included frostnip and frostbite. Hypothermia is most always a nonfreezing condition but when advanced a major risk for death.

Hypothermia: The body can commonly meet a moderate cold challenge and adapt to keep its core temperature above 35 degrees C. With more intense or prolonged cold coupled with inadequate clothing, the core temperature may drop producing more severe symptoms with more hypothermia: a sensation of cold and pain in the exposed body parts (mild hypothermia); less pain but increasing numbness allowing injury unappeciated by the victim; muscular weakness, loss of shivering, dilated pupils and drowsiness as the temperature falls below 33 degrees C; coma around 27 degrees, cardiac arrest around 20 degrees C and loss of brain function around 17 degrees. Note that these temperatures are mostly above those found in the modern heated hospital. On occasion the busy and overheated nurse may leave the air-conditioning on in a room of a confused undernourished patient who may kick the blankets off. That very low temperature on the chart may be a real finding!

Frostnip is perhaps a common hazard for skiers. The mildest form of freezing injury, it occurs when the superficial layers of the ear lobes, nose, cheeks, fingers or toes freeze hard and turn numb and white. It is normally reversible with appropriate treatment: gentle rewarming and avoidance of damaging the skin by breaking the ice crystls with rubbing. The extension of freezing through all of the layers of the skin constitutes superficial frostbite and freezing to include muscle and bone constitutes deep frostbite. It occurs when tissue temperature falls below the freezing point due to contact to extremely cold objects (especially metal) or exposure to extreme cold, or if blood flow is obstructed. Local blood vessels may be permanently damaged and circulation cease. Destruction of tissue by ice crystals can lead, for example, to loss of all or a part of a finger, toe or foot. Treatment is begun once the possibility of refreezing is unlikely. The frozen part may be immersed in warm (not hot)water and again rubbing is avoided.

Nonfreezing cold injuries can also lead to tissue loss. Chilblains are generally a mild injury incurred by exposure for several hours to air temperatures from 0°C to as high as 16°C. It is manifested by local redness, swelling, tingling, and pain. Immersion foot has been historically a military problem occurring in soldiers whose feet have been wet and subject to temperatures up to 10 degrees C for days or weeks. Damage to nerve and muscle tissue is associated with symptoms of tingling, numbness, itching, pain and swelling of the legs, feet, or hands. In early cases the skin may be red and subsequently turn blue or purple as the exposure continues. In severe cases, gangrene may develop and limb loss ensue. Trenchfoot, again historically a military problem, is a "wet cold disease" resulting from prolonged exposure to dampness and cold from 0 to 10 degrees C.

Role of the Circulator Boot: This patient benefited from the rapid end-diastolic compressions which (a) stimulate the local producton of fibrinolysins, nitric oxide and prostacyclin; (b) allow each arterial waveform to enter the treated area; (c) empty the veins and lymphatics and (d) disseminate the entering arterial volumes throughout the treated area (much like one disseminates water through a partly wetted sponge when one squeezes it). His skin color and tissue turgor improved daily with his treatments. The plastic boot bag surrounding the leg prevents cooling from evaporation and air currents. The boot may be compared to a heat pump: The air warms up as it is compressed and cools as it expands into the boot. The boot may be used as a means to warm the legs if the compressed air lines are placed in hot water during the treatment. The hypothermic patient with circulatory failure may also benefit from the cardiac-assist action of the Long Boots.

Reperfusion injuries and free radicals: Blaumik et al (1995) reviewed the relationship between cold injury and the generation of free radicals on rewarming and reperfusion. Similar arguments are offered in the surgical vascular literature regarding reperfusion injury after both peripheral vascular and cardiac procedures. In all cases, it serves the patient well to regain adequate circulation to the challenged part as quickly as possible. To those of us in the Circulator Boot world, the common practice of observing an ischemic part to see where it will demarcate is regretable.