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Everything you need to know about heat stroke and heat exhaustion

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Margaret Butler was enjoying a backyard barbecue last summer, barely aware the heat of the day had risen to sweltering temperatures. All of a sudden, she felt dizzy, tingly in the fingers, and a bit nauseated. She tried to communicate these symptoms to her husband, but she couldn’t find the words. “I knew I wasn’t drunk, because I’d had only a glass of lemonade,” recalls the Vancouver mom. “But I felt confused. I didn’t know what was happening and I started to panic.”

Thankfully her husband did know what was happening: Butler was exhibiting the classic signs of heat exhaustion. Her husband quickly moved her into the shade, held a cool, damp washcloth to her face and neck and insisted she drink a glass of water. Butler recovered because she had a moderate encounter with one of the three stages of what health professionals call “heat injury.” If her symptoms had gone untreated, that happy backyard barbecue could have turned tragic.

The three stages of heat injury

Heat cramps are the mildest form, and can strike anyone who exercises rigorously in high temperatures. Painful muscle spasms, usually in the calves, arms, back and abdomen, are due to a loss of fluid from heavy sweating. Stop what you’re doing, rest, replace your fluids with water or a drink containing electrolytes, and gently massage and stretch the afflicted muscles.

Heat exhaustion, in which symptoms include headache, dizziness, weakness, nausea, heavy sweating and a rapid pulse, worsens with high humidity and physical activity. You can usually get the these symptoms under control by moving to a shady spot or, ideally, into air conditioning, a cool shower or bath, applying cold compresses, and replacing lost fluids. If you don’t feel better in an hour, your condition may have progressed to heatstroke, the most serious.

Symptoms of heatstroke include a body temperature above 104 F, confusion, agitation, slurred speech, irrational behaviour, dry, hot skin, rapid pulse, nausea, headache, racing heart, seizures and unconsciousness. Left untreated, heatstroke can damage your brain, heart and kidneys and even be fatal, so immediate medical attention is critical.

Avoid boiling point

“Your body temperature can only function in a very narrow range,” explains Lib Mendonca with the Ottawa St. John Ambulance. “As your body temperature elevates, it loses the ability to control that temperature. It depends on sweat evaporating off your skin to cool you down, and if it’s humid that could be impaired. If you can’t cool yourself down, you could lose consciousness, have seizures and go into convulsions.”

Mendonca says Butler received all the right remedies: moving to a cool space, replenishing her fluids slowly so as not to cause vomiting, which could affect an airway if she’d passed out, and cold cloths on vital points. “Pay particular attention to the arteries that are closest to the surface of the body,” says Mendonca. “Around the neck, the armpits and the groin.”

Mendonca says the quickest way to cool someone suffering heat exhaustion or heatstroke is to immerse him or her in cool water, either a bathtub or pool, but if that’s not possible, cold compresses will help. “If you’ve called 911 and you’re waiting for the ambulance, you can do a pretty good job of cooling the person down.”

At the hospital, emergency room personnel may immerse you in ice water, or use evaporation techniques, such as misting cool water on your skin while fanning warm air over your body. They may also wrap you in special cooling blankets and apply ice packs to your groin, neck, back and armpits. You may also require intravenous fluids and/or a muscle relaxant to stop you from shivering, which increases body temperature, compromising treatment.

Although some sources recommend salt water or salt pills, Mendonca believes they’re unnecessary in most cases since we don’t lose excessive amounts of salt through sweat, and it’s readily replaced through an average diet. As for electrolyte drinks, he says serious athletes and marathon runners may benefit, but simple water is best for the rest.

Hot jobs

Mendonca says those whose jobs require them to work outside — roofers, flag people, road workers, etc. — should take frequent breaks out of the sun, stay fully hydrated and use cooling techniques such as fans and misting. Firefighters are at particularly high risk of overheating because of their heavy clothing and close proximity to fires. Mendonca says the Ottawa Fire Department has pioneered an ingenious method of protecting themselves.

“They created this simple, folding chair that, instead of arm rests, has a trough full of cold water,” he explains. “When the firefighters cycle out of rotation at a fire, they strip off their gear, expose their arms, and sit there with their arms immersed in the cold water trough for 15 minutes or so. It very dramatically reduces their core temperature, keeping them from heat stress.”

Cool it

While most of us are unlikely to improvise a firefighter’s cool seat, we can still avoid any kind of heat injury by being cognizant of our time in the sun and how we’re feeling. Stay inside or in the shade during the middle of the day when it’s hottest; keep plenty of fluids (not alcohol) on hand, but not too cold, which could cause stomach cramps; apply sunscreen; wear loose, light-coloured clothing and a wide-brimmed hat. The very old, the very young, those with certain medical conditions, and the overweight are particularly susceptible to the sun’s punishing rays. Some medications, such as those to treat diabetes, depression or ADHD, can also exacerbate the effects of high heat.

And, according to Health Canada, over the next three decades, the number of extremely hot days in a year is expected to more than double in some areas of the country. For tips on how to prepare and protect yourself from the rising mercury, check out Health Canada’s website.