HEAT DISORDERS

By Trevor Shewfelt, Pharmacist at the Dauphin Clinic Pharmacy

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The information in this article is intended as a helpful guide only. It is not intended to be used as a substitute for professional advice. If you have any questions about your medications and what is right for you see your doctor, pharmacist or other health care professional.

A few years ago, I was volunteering at Country Fest and working at the Kinsmen Bar. It wasn’t that hot out, maybe 25 C. The work area was shaded and I was allowed to take breaks. Apparently, I didn’t take enough of them, and didn’t consume enough fluids. At the end of my shift I was dizzy, and nauseous. What was wrong with me? What did I do? First, let’s talk about different heat disorders. Having your body get too hot is dangerous. To see how heat leaves the body, let’s go back to high school physics.

It takes energy for water to go from a liquid state to a vapour. When the thin film of perspiration on your skin changes into water vapour, it takes heat energy away from your body and you cool down. Heat loss through perspiration accounts for about 30% of the body’s heat loss. This is why you feel much cooler if it is 25oC and 0% humidity than if it is 25oC and 100% humidity. At 0% humidity you can think of the air as empty of water vapour, so the perspiration on your skin can easily change to vapour, and take heat away from you. At 100% humidity, the air is full of water vapour so the perspiration on your skin stays as liquid water and doesn’t cool you down. So if you exercise when it is warm and humid, your body will produce extra heat, but your perspiration won’t be able to remove it and you can dangerously over heat.

What are some of the heat disorders? Heat edema is quite mild and is when the hands or feet swell. Heat cramps are caused by sore muscles especially in the arms, legs, and stomach. Heat cramps can be the first sign of heat exhaustion which is more serious. Heat syncope is dizziness or fainting from the heat and is more serious. Heat exhaustion has symptoms like weakness, dizziness, nauseau, vomiting, and headache. It is when the core body temperature rises above 38 C but less than 40.5C. Heat stroke is a medical emergency. People die from heat stroke. It is when the core temperature goes above 40.5 C. Get heat stroke patients to an emergency room.

So what actions should be taken for which symptoms? If the person losses consciousness, is confused or hallucinating, has convulsions, has trouble breathing, is vomiting a lot, or has hot dry skin with no sweat, it could be heat stroke so get the person to an emergency room or call an ambulance. If the person is nauseated and vomits a little, has headaches, cramps, dizziness or tiredness this may be heat exhaustion. Take off excessive clothing and get the person somewhere cool. Have them drink fluids. Wet the skin with cool or lukewarm water. Elevate the feet or hands if they are swollen. If the person doesn’t recover in 2-3 hours get them to an emergency room. Again, if in doubt about how serious the heat disorder is, assume heat stroke and get them to an emergency room.

Some medication can make it more likely to have heat related problems. Certain antipsychotics and antidepressants, diuretics and beta-blockers can inhibit sweat production. Cocaine constricts the blood vessels to the skin which can lead to over-heating. Amphetamines (including Ecstasy) can disrupt the hypothalamus which is the part of the brain that effects heat regulation.

To prevent heat disorders:
• drink plenty of cold water on hot summer days, especially before and during heavy physical exercise
• avoid heavy outdoor activity from 10 am to 3 pm
• stay out of the sun if possible and take lots of rest breaks (drink fluids during these breaks)
• get used to hot weather slowly over several days by gradually increasing you activity out in the hot weather

So what did I do when I got heat exhaustion? I had a cool shower, stayed where it was air conditioned and drank Gator Aid. I should have been smarter and drank more fluids before and during my activities.

As always if you have any questions or concerns about these conditions, ask your pharmacist.