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Summer’s heat and humidity effects

July 21, 2012
By C. Paul Martin, M.D. , Marshall Independent

One cannot be surprised at the variability in temperatures we experience here in Minnesota! Although we certainly merit national press reports when our subzero temperatures occur in winter, our recent nearly 100 degree readings in late June and July quickly reminded us that this summer has been affecting our health.

Most of us are ill-prepared for the high temperatures and humidity. This predicament underlines the importance of our knowledge regarding the effects of heat on our bodies. Significant illnesses caused by high temperatures, humidity, and sun exposure, even in our mild Minnesota summers, can occur and emphasize the need for all of us to increase our awareness of these potentially serious problems.

The beneficial and harmful effects of the sun on a chronic (long-term) basis have been discussed in this column in past years.

Today we direct our attention to the often uncomfortable and sometimes severe results of high temperatures and resultant sun exposure, namely heat edema, heat syncope, heat cramps, heat exhaustion, and heat stroke. These conditions are precipitated by high temperatures and sun exposure and modified by pre-existing factors of age, infirmity, illness, medications and alcohol use.

Heat edema is a common yet usually minor result of the warm temperatures of spring and summer on dependent venous flow. Increased fluid retention in the lower legs or "shin" areas and mild discomfort in these areas are often experienced by middle-aged and older females and men and women with varicose veins. Moderate ambulation, support hose and/or leg elevation in a cooler environment is therapeutic for this self-limited illness. Medications are not usually required.

Heat syncope (fainting) is a sudden loss of consciousness, usually related to increased skin blood flow to cool the skin, superimposed on mild dehydration from sweating or medication. People using diuretics or beta-blocking agents for blood pressure control may experience this sometimes frightening but minor occurrence. Fluid replacement with water, clear liquids or Gatorade-like beverages and moving to a sheltered and cooler place will treat this problem and prevent recurrence.

Heat cramps or painful muscle contractions, especially in the lower legs, are usually related to salt depletion. The person is calm, cool, with normal vital signs. Vigorous activity in the sun usually precedes the cramps. Treatment includes a cooler environment, oral liquids with salt replacement using Gatorade or similar liquids, and rest from activity. Note: Salt tablets are now no longer recommended for any heat-related illness.

The two more serious heat-related illnesses include heat exhaustion and heat stroke. Heat exhaustion is related to prolonged activity in a sunny, hot environment and often causes weakness, thirst, headache, fatigue and an anxious state of mind. Findings in heat exhaustion are a mildly elevated temperature (100.4 degrees), a fast pulse, moist skin (sweating is present) and some muscle discomfort. Treatment is a cool environment, increased fluids orally, salt replacement as above and active cooling with fans, ice, etc. These people are ill and must be watched carefully!

Rarely, people affected with heat exhaustion progress to heat stroke, a life-threatening emergency, in which they exhibit hot, dry skin, minimal sweating, an elevated temperature (105 degrees), and impaired consciousness. This situation may be seen in the older population, the debilitated, and those persons taking medications that decrease sweating or interfere with temperature regulation, e.g., some blood pressure medications. Vigorous work or exercise, increased alcohol or sedating drugs, and a hot, closed work environment are also contributing factors. People in this situation require hospitalization and intensive care to rapidly reduce their temperature.

We can partially modify the external environment. Avoid prolonged sun exposure, certain drugs and alcohol. Don't forget your hat, protective beach clothing, sunscreen, and, most important, use COMMON SENSE when outdoors!

At the present time, we can greatly modify our inside environments because of the invention of air-conditioning, usually associated with the work of Willis Carrier. His invention of air cooling by the evaporation of liquids is probably one of the most significant socio-economic domestic improvements in the history of the United States. An intriguing and succinct history of the development of air-conditioning in homes and workplaces has recently appeared in the Wall Street Journal Opinion section (WSJ, 10 July 2012). It is a good read!



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