For those working in cold environments, it’s important to know that a number of medical problems falling under the category of “cold stress” may be faced. This can affect those working in freezing or near freezing temperatures, either outside or inside in unheated spaces.
The most life-threatening cold stress injury is hypothermia. Hypothermia is the fall in body temperature that affects all body systems, especially the brain where it lowers the ability to react and think clearly to avoid danger. Wet skin increases the conductive loss of heat by about 30 times, but the major loss of heat with dry skin comes from radiation loss.
Initial symptoms include shivering, loss of coordination and confusion, and lead to slow pulse, slow breathing and coma. Shivering as a means of preserving body heat occurs at a body temperature of about 95 degrees Fahrenheit, but is lost as the temperature falls below about 90 degrees. Unconsciousness will follow at a body temperature below about 82 degrees.
Treatment includes moving the victim to a warm area and covering them with warming blankets, especially the core of the body (trunk, neck and groin). Wet clothing should be removed and the victim should try to drink warm fluids, but not alcohol, if they are awake enough to swallow safely. If there is no pulse, call 911 immediately and begin CPR. The heart becomes sensitive to rhythm problems below a body temperature of 86 degrees. If the victim is unconscious, avoid excessive movement of the body that can set off arrhythmias. Cold-water immersion would be treated the same way with the extra caution not to move the body.
Frostbite is another cold stress injury that presents a major threat in cold work environments. Fingers, toes, nose and ears are most susceptible to frostbite since they readily shunt blood to the core in cold environments. Wind chill and wetness accelerate the damage. When skin temperature falls below 50 degrees, sensation in the skin is lost, and freezing occurs when skin temperature falls below 32 degrees. Damage occurs to cells due to direct cold injury, ice crystal formation and damage to small blood vessels in the skin.
Symptoms include numbness, tingling, dull ache and waxy and pale skin. As the area rewarms, swelling of the tissues and large blisters appear. Blood-filled blisters, blackened areas and lack of swelling in rewarmed tissues are all signs of poor recovery. Rapid rewarming, which can take 45 to 60 minutes, is most desirable and should be accomplished with water just above body temperature, about 104 to 108 degrees Fahrenheit.
However, if out in the field where there is a chance of rewarming and refreezing, avoid attempts at rewarming until danger of refreezing is eliminated. There will be considerable pain with rewarming and this may need to be treated. Forced air rewarming may also be possible in the field. Remove any wet clothing and avoid rubbing or massaging the areas as well as walking on frostbitten feet or toes. In the field, you can use warmer body parts to start rewarming, such as placing the fingers under the armpits. All cases of frostbite should ultimately be treated by medical personnel, because frostbite can result in permanent problems.
The key to a safe work environment in the cold is the use of layered clothing, mittens instead of gloves, covering of face and ears, avoidance of wet clothing and reducing time in the cold.
Dr. Scott DeHart is the medical director of Mount Nittany Physician Group Occupational Health.