We talk about the dangers of working in the heat frequently, but rarely discuss the cold. Since I live in the desert we see extremes of both. Surprised? The desert often sees a 40-plus degree drop as the sun sets in the winter.
The cold injures workers and is just as dangerous as the heat. Interestingly enough, workers will try to tough out both heat and cold injuries; often only notifying the employer when significant damage has already been done.
Certain factors predispose to cold stress injuries. Lower temperature and increased wind speed are well known as the “wind chill factor” (10 degrees or less and 25 mile-per-hour winds are a treacherous combination). Physical exhaustion, poor physical condition, and disease (hypertension, diabetes, low thyroid) are all risk factors. Wet or inadequate clothing will considerably shorten the time it takes to get into hypothermia trouble.
Humans are warm-blooded, and burn enough calories to stay around 98.6 F. This is your core body temperature, which allows optimal function of your heart, lungs, and brain among other things. Your body will defend your core temperature even if it means the loss of toes or fingers. As your body starts to cool due to low environmental temperature, you will start to shiver, using your muscles to generate heat. You are feeling cold at this point, but everything still works.
Drop a few more degrees, to a 95-degree core body temperature, and you will stop shivering, and the blood from your extremities will be shunted to keep the core warm. This, of course, makes the temperature of the limbs drop faster and can put fingers and toes at risk of freeze damage (frostbite). You are getting confused and uncoordinated at 95 degrees, but you still have blood pressure and circulation, so you have a good chance of surviving. Cool a bit more and the breathing becomes shallow and the pulse weak. You cannot help in your own rescue because you are too weak to stand and walk, and may be unconscious. Death is not far away.
Frostbite is freezing damage to the tissues. It usually starts at the thinnest body parts (high surface area to mass), and the most distant from the heart – the toes and fingers. There may be only exposed skin damage, or the toe or finger may literally freeze. Despite the immense fortunes optimistic people spend to keep their bodies in liquid nitrogen, freezing tissue makes cells rupture and cannot be reversed. That means dead tissue, most frequently a toe. Amputation keeps infection from spreading and killing more tissue.
Mountaineering stories tell of a frozen, dead climber with his coat and gloves discarded nearby. That is the profound confusion that can occur with low core body temperatures.
Many people spend time in the outdoors, because of work or play: Police, construction workers and firefighters as well as skiers, snowmobilers and skaters. Hypothermia is preventable with some preparation. Think plenty of layers, and wear a hat. It takes a lot of blood to grow hair, so the scalp is a natural radiator – cover it and you loose a lot less heat. Layers on the trunk and extremities trap warm air and insulate you in the same principal as a thermos. More layers means more trapped air; a better thermos. Watch friends or colleagues for signs of hypothermia, and be willing to intervene if necessary.
Treating a person with hypothermia involves evacuating them to a warm, dry place. Remove any wet clothing and wrap them in multiple layers of blankets. Put hot packs under the arms, at the sides and at the groin. Then, wait patiently for the paramedics (whom you called first).
Be careful out there.
Donald Bucklin, MD (Dr. B) is a Regional Medical Director for U.S. HealthWorks and has been practicing clinical occupational medicine for more than 25 years. Dr. B. works in our Scottsdale, Arizona clinic.
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