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Heat: Adjust, hydrate, stay safe

August 2008 – Vol. 12, No. 8

Editors: Janet M. Pollard, MPH; and Carol A. Rice, Ph.D., R.N.

“Your body is always working to keep balance between how much heat it makes and how much it loses. Your brain is the thermostat. It sends and receives signals to and from parts of your body that affect temperature, such as the spinal cord, muscles, blood vessels, skin, and glands that make substances known as hormones. Too much heat causes sweating. When sweat dries from your skin, the surface of your body cools, and your temperature goes down.”¹ If we allow our bodies to adjust (PDF) to the heat and take precautions (e.g., getting enough fluids, taking breaks from the heat, etc.), our bodies can adapt and adjust. If precautions are not taken, we become susceptible to heat illness.

Avoiding Heat Illness: The adverse effects of heat

Excessive exposure to a hot environment, especially while active or working, can bring about a variety of heat-induced disorders.¹⁰ “Being hot for too long can cause many heat illnesses, all grouped under the name hyperthermia (hy-per-ther-mee-uh).”¹

Let’s take a look at some of these conditions so we can learn how to avoid them and how to treat them when necessary.

Heat cramps are painful, involuntary muscle spasms, usually in the abdomen, arms, or legs, typically occurring during heavy/ strenuous exercise or activity in hot environments.^2,3 Heavy sweating is usually involved in heat cramping. The sweating depletes the body of moisture and salt. Low levels of salt in the muscles may be the cause of heat cramps.³

Treatment: Apply firm pressure or gentle massage to the cramping muscle to relieve the spasm. Stop all activity, and sit quietly in a cool place. Drink clear juice or electrolyte-containing sports drinks to replenish salt and fluids (PDF). If vomiting occurs, discontinue fluid intake. Practice gentle stretching of the area, and apply ice if necessary. If the cramps don’t go away within 1 hour, call your doctor.^2,3,4,5

Heat edema is a swelling of the ankles and feet when you get hot.¹

Treatment: Putting your legs up (elevating them) should help. If that doesn’t work fairly quickly, check with your doctor.¹

Heat exhaustion is the most common heat illness and often comes on suddenly. It is caused by decreased blood volume due to dehydration. Symptoms may include dizziness/feeling faint, headache, nausea, profuse sweating, clammy/cool skin, rapid/ weak pulse, body temperature at or slightly below normal, low-grade fever, low blood pressure, and ashen/pale appearance.^2,5,6

Treatment: Get the victim out of the sun immediately. Lay the person down, elevating the legs and feet slightly. Loosen or remove the person’s clothing. Cool the person by applying cool, wet cloths (changing them often) or spraying or sponging him/her with cool water. Move the victim to an air-conditioned environment, or fan him/her if air conditioning is not available. Give sips of cool (not iced) water or a sports drink containing electrolytes. If nausea occurs, discontinue the drink. If vomiting continues, seek immediate medical attention. Monitor the person carefully. Heat exhaustion can quickly become heat stroke if left untreated. Call 9-1-1 if fever is greater than 102 °F, fainting, confusion, or seizure occur.^2,5,6

Heat rash is a skin irritation caused by excessive sweating during hot, humid weather. It can occur at any age but is most common in young children. Heat rash looks like a red cluster of pimples or small blisters. It is more likely to occur on the neck and upper chest, in the groin, under the breasts, and in elbow creases.⁴

Treatment: The best treatment for heat rash is to provide a cooler, less humid environment. Keep the affected area dry. Dusting powder may be used to increase comfort. Treating heat rash is simple and usually does not require medical assistance.⁴

Heat stroke is a life-threatening medical emergency. It can result in permanent disability or death if emergency treatment is not provided. Heat stroke occurs when the body is unable to regulate its temperature.³ The body’s temperature rises rapidly; the sweating mechanism fails, and the body is unable to cool down. Body temperature may rise to 106°F or higher within 10–15 minutes.⁴ Warning signs vary but may include:

• an extremely high body temperature (above 103°F, orally);
• red, hot, and dry skin;
• no sweating;
• rapid, strong pulse or heartbeat;
• rapid, shallow breathing;
• elevated or lowered breathing;
• throbbing headache;
• dizziness;
• nausea;
• confusion;
• irritability; and/or
• unconsciousness.⁴

Treatment: Have someone call 9-1-1 while you begin cooling the victim in whatever way you can. Here are some steps to take (time is crucial, so use/do what is at hand):

• Get the victim to a shady area.
• Cool the victim rapidly using whatever methods you can. For example, immerse the victim in a tub of cool water; place the person in a cool shower; spray the victim with cool water from a garden hose; sponge the person with cool water; or if the humidity is low, wrap the victim in a cool, wet sheet and fan him or her vigorously.
• Monitor body temperature, and continue cooling efforts until the body temperature drops to 101–102°F.
• If emergency medical personnel are delayed, call the hospital emergency room for further instructions.
• Do not give the victim fluids to drink.
• Get medical assistance as soon as possible.^4,7

Heat syncope is a sudden dizziness that may come on when you are active in the heat. If you are not used to hot weather or take a form of heart medication known as a beta blocker, you are more likely to feel faint when in the heat.¹

Treatment: Putting your legs up and resting in a cool place should make the dizzy feeling go away.¹

Dehydration: Our bodies’ need for fluid

One of the major contributors to heat-related illness is dehydration. Dehydration is a condition that occurs when you don’t have enough water in your body to carry out normal functions.¹⁰

“Water is your body’s principal chemical component, comprising, on average, 60 percent of your weight. Every system in your body depends on water. For example, water flushes toxins out of vital organs, carries nutrients to your cells, and provides a moist environment for ear, nose, and throat tissues.”¹⁰

If we don’t keep water in balance, it can lead to dehydration. For our bodies to function properly, we must replenish its water supply by consuming beverages and foods that contain water (PDF).

But how much water should we drink each day? How much should we take in through food? Do we need 8 glasses a day?

Approximations of water needs for the average healthy adult living in a temperate climate come from looking at how we lose and take in fluids. Every day, we lose water through our breath, sweat, urine, and bowel movements (typically about 2.5 liters are lost each day). Food accounts for about 20 percent of total fluid intake per day, so we need to replenish the remaining 2 liters (8–9 cups) by consuming water or other hydrating beverages. Note: Men may need to consume slightly more than women—up to 3 liters (13 cups).¹⁰

These guidelines are rough estimates and don’t take special circumstances (PDF) into account. Actually, water needs depend on many factors, including your health status, your size, how active you are, and where you live.¹⁰ For instance, when you exercise, you need to keep hydrated. An extra 1 or 2 cups of water should suffice for short bouts of exercise, but intense exercise lasting more than an hour (for example, running a marathon [PDF]) requires additional fluid. How much additional fluid is needed depends on how much you sweat during the exercise, but 13 to 26 ounces (or about 2 to 3 cups) an hour will generally be adequate, unless the weather is exceptionally warm.”¹⁰ Hot or humid weather can make you sweat and requires additional intake of fluid to help lower your body temperature and replace what you lose through sweating. Heated indoor air can also cause your skin to lose moisture during wintertime, increasing your daily fluid needs. You may need more water in wintertime if you sweat when wearing insulated clothing. Further, altitudes greater than 8,200 feet (2,500 meters) may trigger increased urination and more rapid breathing, which use up more of your fluid reserves.^10,11

Are You Getting Enough Fluids? Monitoring your body

To make sure you are getting enough water, you can monitor your body in the following ways:

Check your urine. If your urine is dark yellow or amber in color¹¹ or small in quantity, it is likely concentrated with metabolic wastes, and you need to drink more fluids. Your urine should be a pale yellow color and normal quantity when you are getting enough fl uids. If you are not going to the bathroom every 2–4 hours, you are not drinking enough.

Weigh yourself. By weighing yourself before and after work or exercise, you can monitor the pounds lost during your activity. For every pound lost, you should drink at least 2 cups of fluid. In hot weather, those who work outside or exercise may find that they’ve sweat off as much as 5–8 pounds. This is water loss, not fat loss.

Monitor your feelings. If you feel chronically fatigued, lethargic, or have a constant headache, you may be dehydrated. Monitor yourself and others for impaired performance, heat cramps, chills, clammy skin, rapid pulse, gastrointestinal problems, dizziness, dry mouth, hallucinations, no sweat or urine, swollen tongue, unsteady walk, high body temperature, refusal of water, vomiting, and changes in levels of consciousness. These may all be signs and symptoms of severe heat problems.^12,13

Note: You should always replenish your fluids at regular intervals before you become thirsty. Thirst is not an indicator of when fluids are needed. Some individuals may even refuse water when under heat stress.

When to Be on High Alert: The weather report

If the weather report says we’re having a heat wave and the heat index is 101°F, what does that mean, and how do our bodies adjust (PDF)?

Heat wave. A heat wave is defined as a prolonged period of excessive heat and humidity. The National Weather Service steps up its procedures to alert the public during these periods of excessive heat and humidity.²

Heat index. The heat index is a number in degrees Fahrenheit that tells how hot it really feels when relative humidity is added to the actual air temperature. Exposure to full sunshine can increase the heat index by 15°F.²

Extreme heat. Extreme heat is defined as temperatures that hover 10°F or more above the average high temperature for the region and last for several weeks.⁴

For information on heat and weather concerns in your area, consult the National Oceanic & Atmospheric Administration website. FEMA (the Federal Emergency Management Agency) and the American Red Cross give the following tips if you are expecting or experiencing extreme heat conditions:

In preparation…

• Install window air conditioners snugly; insulate if necessary.
• Check air-conditioning ducts for proper insulation.
• Install temporary window reflectors (for use between windows and drapes), such as aluminum foil-covered cardboard, to reflect heat back outside.
• Weather-strip doors and sills to keep cool air in.
• Keep storm windows up all year.
• Cover windows that receive morning or afternoon sun with drapes, shades, awnings, or louvers. Outdoor awnings or louvers can reduce the heat that enters a home by up to 80 percent.

In the heat…

• Adjust. If you have traveled to a warmer climate than you live in, are beginning work in the heat, or are an athlete (PDF) beginning to practice in the heat after an off season – allow your body to adjust to the heat by limiting your activity in it at first.
• Slow down. Avoid strenuous activity/work during the warmest part of the day. If you must do strenuous activity, do it during the coolest part of the day, which is usually in the morning between 4:00 – 7:00 a.m. Use a buddy system (to watch for signs of heat illness) when working in extreme heat, and take frequent breaks.
• Stay indoors as much as possible, and limit exposure to the sun.
• If air conditioning is not available, stay on the lowest floor, out of the sunshine.
• Consider spending the warmest part of the day in public buildings such as libraries, schools, movie theaters, shopping malls, and other community facilities.
• Wear loose-fitting, light-weight, light-colored clothing. Light colors will reflect away some of the sun’s energy.
• Protect the face and head by wearing a wide-brimmed hat.
• Drink plenty of water regularly and often. Your body needs water to keep cool. Note: People who have epilepsy or heart, kidney, or liver disease; or are on fluid-restricted diets; or have a problem with fluid retention should consult a doctor before increasing liquid intake.
• Drink plenty of fluids even if you do not feel thirsty.
• Water is the safest liquid to drink during heat emergencies. Avoid drinks with alcohol or caffeine in them. They can make you feel good briefly, but they make the heat’s effects worse on your body. This is especially true of beer, which dehydrates the body.
• Eat well-balanced, light, and regular meals. Eat small meals, and eat more often. Avoid foods that are high in protein, which increase metabolic heat.
• Avoid using salt tablets unless directed to do so by a physician.
• Check on family, friends, and neighbors who do not have air conditioning and who spend much of their time alone.
• Never leave children or pets alone in closed vehicles. Even when you crack or roll down windows, temperatures inside a vehicle climb much higher than the outdoor temperature.^2,14

By taking some necessary precautions and being aware of the signs and symptoms of heat illness, we can enjoy the hot outdoors without negative effects…and provide help if heat concerns do arise. For further information, see the following resources:

• Avoid Dehydration during Sports (PDF)
• Hyperthermia: Too Hot for Your Health (PDF).

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Electric Fans

Many people who do not have air conditioning use electric fans to try to keep cool. Electric fans do not cool the air, but they can help sweat to evaporate, which cools the body.² Though electric fans may provide comfort, when the temperature is in the high 90s, fans will not prevent heat illness.¹ The fan can cause sweat to evaporate too quickly from the skin and accelerate dehydration.⁸ Additionally, older people don’t usually sweat as much as younger people. For this reason, older individuals should not use fans as their sole means for staying cool because fans work only when we sweat.⁹ In fact, a person who sits inside a closed room with no air conditioning and a fan blowing on them can have increased dehydration; when the room is hot, it actually increases thermal stress.⁸

If you need a fan to stay cool in hot weather, don’t sit directly in front of the fan, and always open a window for ventilation when running a fan.⁸ A better way to stay cool is to take a cool shower or bath, spray the body with water to get cooling from evaporation,⁹ or get to a place that has air conditioning during the hottest part of the day.¹ If you need help finding a place to stay cool or getting transportation, call a friend, family member, or your local health department.

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This document is meant for educational purposes only and is not intended to replace the advice of your doctor or other health care provider.

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References:

1. National Institute on Aging (2005) Age page – Hyperthermia: Too hot for your health. Retrieved August 25, 2006. From http://www.niapublications.org/agepages/PDFs/
   Hyperthermia-Too_Hot_For_Your_Health.pdf
2. American Red Cross (2001). Heat waves. Retrieved August 24, 2006. From http://www.redcross.org/services/disaster/keepsafe/heat.html
3. Mayo Clinic (2006). Heat cramps: First aid. Retrieved August 24, 2006. From http://mayoclinic.com/health/first-aid-heat-cramps/FA00021.
4. Centers for Disease Control (2006). Extreme heat: A prevention guide to promote your personal health and safety. Retrieved August 25, 2006. From http://www.bt.cdc.gov/disasters/extremeheat/heat_guide.asp.
5. National Athletic Trainers’ Association (2003). Activity health tip #1: Heat illnesses. Retrieved August 25, 2006. From http://www.nata.org/consumer/heatillnesses.htm.
6. Mayo Clinic (2006). Heat exhaustion: First aid. Retrieved August 24, 2006. From http://mayoclinic.com/health/first-aid-heat-exhaustion/FA00020.
7. Mayo Clinic (2006). Heat stroke: First aid. Retrieved August 24, 2006. From http://mayoclinic.com/health/first-aid-heatstroke/FA00019.
8. Pirisi, A (2006). Many don’t heed heat advisories. Retrieved August 24, 2006. From http://news.healingwell.com/index.php?p=news1&id=533946.
9. Reinberg, S (2006). Heat-related deaths in the U.S. on the rise. Retrieved August 24, 2006. From http://domains.e-healthsource.com/index.php?p=news1&id=534068.
10. Mayo Clinic (2006). Water: How much should you drink every day? Retrieved August 24, 2006. From http://mayoclinic.com/health/water/NU00283.
11. Mayo Clinic (2005). Dehydration. Retrieved August 24, 2006. From http://mayoclinic.com/health/dehydration/DS00561.
12. Clark, M. (1997). Sports Nutrition Guidebook. Brookline, MA: Human Kinetics, pp 144-163.
13. American Red Cross (1991). First Aid: Responding to Emergencies. St. Louis, MO: Mosby. Lifeline, pp 338-339.
14. Federal Emergency Management Agency (2006). Are you ready? Extreme heat. Retrieved August 24, 2006. From http://www.fema.gov/areyouready/heat.shtm.