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By Christopher V. Flores, M.D.
As seasonal temperatures rise, we get our cars serviced to ensure their radiators and cooling systems work properly, and we schedule our home air conditioner maintenance. But we seldom prepare our bodies for the hot weather ahead. Every summer, heat-related illness and heatstroke befall thousands of people, often fatally. We can curb most of these situations by planning our summer health just as we prepare our homes and automobiles for high temperatures.
Handling the Heat
The human body is designed to maintain a temperature of about 98.6 degrees. There are two main ways we keep ourselves from overheating: radiation and evaporation. In the first, we give off heat to the surrounding environment, especially when the air is cooler than our body. In the second, glands in our skin produce a salty, watery liquid when we are hot; as this fluid evaporates into the surrounding air, we lose excess heat.
There are two additional ways we cool our bodies: convection, the diversion of blood circulation to move heat from our inner core to the surface area of our bodies; and conduction, in which we directly transfer heat by touching a cooler object with our skin. In a hot environment, where the temperature is greater than 98.6 degrees, evaporation is really the only mechanism we can use to keep cool. Genetic and hereditary factors influence how each of us handles heat stress. Several medical conditions (and their treatments) can limit our ability to rid our bodies of excess heat. Fortunately, we can help our bodies adapt to the heat and improve our performance in hot summer weather — and minimize the risk of heat-related illness while we’re at it.
How We Adapt
Research shows that the human body adapts well to hot environments. In order to maximize the effect of radiation, circulation to the skin increases and our hearts pump more blood to the surface of our bodies.
To better exploit evaporation, our skin increases the volume of sweat it can produce, while decreasing the concentration of salt in our perspiration. How-ever, this adaptation will not occur without adequate time for the body to adjust and adequate water intake to increase blood volume and sweat output. This is why acclimatization and hydration are so critical to preparing our bodies to deal with heat.
Acclimatization and Hydration
The better our physical fitness is before a heat wave begins, the easier we adapt. Studies have shown that regardless of a person’s age, good physical conditioning decreases the likelihood of heat-related illness and heatstroke. Also, the higher our body mass, the more difficult it is for us to dissipate heat from our body surface; tall, thin people usually have an easier time keeping cool than short, heavy individ-uals. Preseason workouts to improve aerobic conditioning and promote weight loss ease our transition to the summer.
Once the heat kicks in, it takes at least six or seven days for us to begin to adapt to increased ambient temperatures. The optimum time we should allow for our bodies to acclimate is two weeks, so that we are fully adjusted to the hot weather. We should limit our activities and realize that even at rest our bodies are taxed when we are dealing with scorching summer days. One-and-a-half to two hours of activity per day during the first week gives our skin and circulation time to ramp up their functions to adapt to hot weather. Stepping up activity slowly over the next week maximizes our acclimatization.
Ideally, we should minimize our reliance on air conditioning, because retreating into an overly chilled environment works against our efforts to acclimate. All our hard work at ac-climatization will be wasted if we sleep in a frosty room at night. Keeping the thermostat set at 80 degrees or above will not only save us money, but also preserve our hot-weather adaptation.
Hydration is critical for successful adaptation to days when the temperature exceeds 100 degrees. Just sitting in the hot sun, we can lose a liter (about a quart) of water from sweat every hour. If we walk or perform some other exercise, we can double or triple this amount. It is important to drink adequate water before any physical activity and replenish regularly, even if we do not feel thirsty. Waiting until we are thirsty is like waiting until the engine shuts off before putting fuel into the car. It takes a while for our thirst sensors to realize that we are getting low on water, so it is best to keep ahead of trouble and drink about a liter per hour — and more if we are working in extreme heat for long periods of time.
Individuals with certain medical conditions, such as heart or kidney disease, often must limit their water intake. They should check with their doctors about how much water they can safely drink.
Plain water is the best form of hydration. However, after several hours of heavy sweating, we begin to lose salts in the form of so-dium and potassium, and we crave energy in the form of carbohydrates, so sports drinks like Gatorade and PowerAde are useful after strenuous activity.
What Might Stand In Your Way
Common medications can work against our bodies’ efforts to adapt to the heat. Over-the-counter drugs like Benadryl (taken for allergies) and Sominex (a sleeping aid) contain diphenhydramine, which has anticholinergic effects that interfere with our biological mechanisms to cool off. Many off-the-shelf treatments for colds and seasickness have the same side effects. A pharmacist can help individuals decide which medications are best to avoid in the middle of summer.
Some prescription medications also impair our physical ability to vent excess heat. Heart medications like beta-blockers and diuretics can limit our capacity to increase blood flow to the skin, and drugs that help with diarrhea and bladder control can also inhibit our bodies’ cooling measures. Certain antidepressants and antinausea medications can also make it harder to cope with high temperatures. Ask your doctor if any of the medications you take will hinder your ability to tolerate heat. It may be possible to switch to a drug without this side effect.
Alcohol and caffeine, which act as diuretics, can contribute to dehydration and overheating. They are best avoided on hot days that include activity.
It’s Your Move
By following these tips and seeking the advice of a healthcare professional, you can safely and effectively chill out this summer. The hot climate is something we have to deal with living in the Coachella Valley, although preventive maintenance will help us cope when the heat is on.
Christopher V. Flores is board certified in family medicine.
He is on staff at Eisenhower Medical Center and has a private practice in Rancho Mirage.
Chill Out!
*Keep bottles of water handy, and carry them with you when venturing out in the heat.
*Schedule activities in the early morning when the day is coolest.
*Wear loose, lightweight cotton clothing to allow air to circulate around your skin and evaporate sweat effectively. Tight-fitting, occlusive materials will raise your body temperature dangerously on a hot day.
*Wear white or light colors to reflect the sun’s energy; dark colors trap heat and increase body temperature.
*Wear wide-brimmed hats and sunscreen. Sunburned skin cannot sweat effectively, and the inflammation increases skin temperature.
*Review medications that you take with your pharmacist or doctor.
*Avoid alcohol and caffeine.
Treating Heatstroke
Heatstroke is a medical emergency, and rapid treatment is essential. Symptoms of heatstroke include headache, dizziness, nausea, confusion, fatigue, fainting, hot dry skin that is flushed but not moist, and rapid heartbeat. If heatstroke is suspected, call 911. While waiting for help to arrive, move the victim to the coolest, shadiest space available. Having them lie down with legs elevated will aid circulation to vital organs. Placing cool, moist towels or cloths (ice bags if available) on the body, especially in the armpits and groin areas, will help reduce body temperature. Spray mist on the victim and fan them to simulate sweating. Making a heatstroke victim drink water may make things worse; if their mental status is impaired, they may choke or aspirate liquid into their lungs. They require intravenous fluids to cool them down and replace lost water and electrolytes. |
