Sunday, June 30, 2013

Taking Care of Yourself in High Heat

Chris Carlson/AP

Today is Sunday, June 30, 2013.

The heat wave continues in the West.

In the photo, tourist Cheng Jia from China posed next to the Furnace Creek Visitor Center in Death Valley National Park on Friday.  I have trouble imagining what 128˚F feels like, but at least the humidity in Death Valley is low.  Dry heat is much, much easier to deal with than heat plus humidity.

Lots of record temperatures are being recorded this summer.  The record high temp of all time on earth is 134˚F in Death Valley, California, on July 10, 1913, just short of 100 years ago.  No one will be very surprised if the Death Valley record is broken this summer.

I've talked about heat before.  Everyone's body is a little different in the amount of heat it can take, based on how used to the heat your body is.  There are basically four factors to keep in mind when talking about heat stress. They are temperature, humidity, radiant heat (from the sun or from a furnace, for example, and wind speed.

Wind speed tends to make the air temperature seem cooler to the human body, which is why the weatherman talks about the "wind chill factor" in the winter.  We all know the power of a cooling breeze in the heat of summer.  That's why it's important, if you don't have air conditioning, to at least have a fan to keep air moving around you.

Heat Index Chart: Temperature in Degrees Fahrenheit
Humidity (the relative amount of moisture in the air) tends to make the air temperature seem warmer to the human body, which is why the weatherman talks about the "heat index" in the summer. Besides lowering the air temperature in a room, air conditioning tends to reduce the humidity in the air.  Some people also run dehumidifiers in their homes to deal with excess humidity.  Since dehumidifiers literally pull the water right out of the air, it's important to check your machine often to dump out the water collected in the tray.

 As you can see from the chart produced by the National Weather Service, even at a fairly low relative humidity (40%), caution should be used when the temperature goes above 80˚F (26.6˚C).   The humidity in Furnace Creek, CA, was only about 8% when the picture above was taken.

Radiant heat is also a factor.  We all know that it's much hotter in direct sunlight than it is in the shade.  The expression "100 degrees in the shade" reflects the wisdom that if it's hot in the shade, it's even hotter where the sun is shining.  Firefighters deal with radiant heat from direct exposure to flames in their work.  To protect from radiant heat, a source of shade is essential.  Protective and reflective clothing is also important.

The human body has three ways of defending itself from heat: breathing, sweating, and changing the blood flow.

When it's hot, blood must be circulated to the skin,  which increases skin temperature.The body can then give off some of its heat.  If you're doing heavy work, the body must also make sure plenty of blood gets to the muscles, which means less blood can go to the skin.

Sweating helps the body cool off, but only if the humidity is low enough to allow the sweat to evaporate.  The water and salts lost through sweating must be replaced.

It's important to know the signs of the various levels of heat stress and what to do about them.

Heat rash is the least dangerous heat stress condition.  When the humidity is so high that sweat cannot evaporate, the sweat glands become plugged, and cannot function, and a rash can occur.  The rash will look like small pink or red bumps on the skin,  and the skin will itch or feel prickly.  Getting out of the direct sun is the best cure for this.  Bathing, drying the skin and resting in a cool place will eventually make the rash go away.  Wear loose, cotton clothing, and use lotion to ease the pain or itching.

Fainting, or heat syncope, can happen when blood vessels in the skin and lower part of the body become enlarged.  Blood pools in the legs, reducing the amount of blood to the brain.  The person needs to lie down to restore blood flow to the brain.  To avoid this condition, if you must be on your feet in the heat, keep moving, rather than just standing still.

The next most dangerous condition is called heat cramps.  These are muscle spasms which usually affect the arms, legs and stomach.  Heat cramps are usually due to working too hard in high heat and not enough fluid intake.  The cramps can occur while you're working, after you finish working, or even hours later!  The most important thing to do is rest in the shade and cool down.  Try to drink an electrolyte-replacing drink such as Gatorade.  If the cramps are severe or they do not go away after an hour, seek medical attention.

Electrolytes are minerals in your blood and body fluids that carry an electric charge.  They affect the amount of water in your body, your blood's pH balance (acidity in the blood), and muscle function, among other things.  Common electrolytes include calcium, chloride, magnesium, phosphorous, potassium and sodium. Problems most often occur with levels of sodium, potassium or calcium. If the amount of electrolytes is low, your body becomes dehydrated.  If the amount is too high, your body is overhydrated. 

If you need more potassium in your blood, eat a baked potato or grab a banana for immediate relief.  Prunes and raisins are rich in potassium, and are a good snack to take to the gym.  Calcium-rich foods include broccoli, kale, pinto beans, and wild salmon.  Milk, yogurt and low-fat cottage cheese are good options, too.  For magnesium, add wheat germ, brown rice, avocado, and spinach to your diet.  Magnesium works with calcium to help bones and muscles function properly.  Most of us get too much sodium, rather than too little, so use salt sparingly, but increase your salt intake after strenuous exercise in hot weather if you feel weak, cramp up, or have excessively dry mouth.

Here's a simple recipe for an electrolyte-replacement drink:

1 quart water
1/2 teaspoon baking soda
1/2 teaspoon sea salt
3 to 4 tablespoons raw sugar
1/4 teaspoon salt substitute (potassium chloride)

Combine and stir until all ingredients are dissolved.  For flavor, ad three or four tablespoons of lemon juice.  Serve as is or iced.

Heat exhaustion is more serious than heat cramps.  This occurs when the body's internal cooling system is overworked, but has not yet shut down.  It happens because the body has lost too much water and salt.  Symptoms include cool, moist skin, gray or ashen complexion, headache, intense thirst, dizziness, feeling faint, low-grade fever, heavy sweating, feeling weak or tired, and rapid pulse rate and/or low blood pressure.  Move the person to a cool location and have them lie down with feet elevated.  Loosen or remove clothing, apply cool, wet cloths to the body, and direct a fan towards them. Have them drink cool water or an electrolyte-balancer such as Gatorade, but make sure the liquid is not too cold.  Avoid caffeinated beverages such as coffee, cola, or iced tea.  Monitor the person closely, because heat exhaustion can quickly become heat stroke, a very dangerous condition.  If the person has a fever of 102˚F (38.8˚C), faints, exhibits confusion, or has seizures, call 911 (or the emergency number in your country) immediately. 

Heat stroke is life-threatening, and must be dealt with immediately.  It occurs when the body has depleted its supply of water and salt, and can no longer regulate its own core body temperature.  The body stops sweating, heartbeat is rapid, breathing is shallow and rapid, the victim complains of a throbbing headache, the victim is confused, or the victim loses consciousness or has convulsions.  The body temperature may be 104˚F (40˚C)  or higher.   Call for an ambulance immediately.  Loosen all unnecessary clothing and place the person on his/her side to expose as much skin as possible.  Move to a cool area if possible, out of direct sunlight.  Cool the skin with wet sponges or spraying the person with water and fan vigorously.  Use ice packs on the groin, neck and armpits.  DO NOT GIVE THE VICTIM FLUIDS TO DRINK. 

How can we avoid heat stress conditions?

1.  Remember that the body needs to get used to the heat.  It takes 2-3 weeks to get adjusted to a hot climate. (Remember this if you take a short trip to a hot place!)

2.  Adjust your activity or work schedule.  Try to save heavier work for cooler days or do your heaviest work in the coolest part of the day.

3.  Try to limit your exposure to machines at work and at home that produce heat.  (Ovens, stoves, irons, clothes dryers, hairdryers, etc.)

4.  Remember that work/rest ratios need to change as the temperature and humidity goes up. If you are in the GREEN zone (use the chart at left), use caution and rest when you need to as long as you are doing light work.  (What is meant by "light" depends on how fit you are.)  If you are doing moderate work, the ratio should be 10 minutes' rest for every 50 minutes' work.  This is a good ratio if you are doing yard work on a hot day.  For strenuous work, a 30-minute rest for every 30-minute work period is essential.

If the heat index is in the YELLOW zone, reduce your work to a 40-minute work period followed by 20 minutes of rest for moderate work, and 30 minutes' rest after 30 minutes of hard work. 

When the heat index is in the PINK range, you may need to follow a work/rest ratio for light work if you are out of shape. Listen to your own body.  For moderate work go to 30/30 work/rest, and for strenuous work, rest for 40 minutes after 20 minutes' work.

If you must be active when the heat index is in the RED zone, you must rest for at least 10 minutes after every 50 minutes very light work, even if you are in good condition.  For moderate work, rest for 40 minutes after every 20 minutes' work, and for heavy work, when you cannot avoid it, rest for 50 minutes after every 10 minutes' work.

In all cases, make sure to rest in a shaded place (ideally air-conditioned) and reduce activity to a minimum.  If your clothing is heavy, add 5 degrees (F) to the heat index and work/rest accordingly.  Use a buddy system when doing intense work in extreme heat.

4.  Keep your body hydrated.  Drink 1/2 quart (2 cups) of water per hour in the GREEN zone (using the chart above).  3/4 quart (3 cups)  per hour in the YELLOW and PINK zones, and 1 quart (4 cups) in the RED zone.  Do not drink more than 1 and 1/2 quarts (6 cups)  per hour or 12 quarts (48 cups) per day.   Remember that when you are working, Gatorade helps, but don't overdo the Gatorade if you don't need it, because of the amount of calories.   The key is to drink BEFORE you are thirsty. 
Avoid caffienated beverages such as cola, black or orange tea, or coffee.  Also avoid alcohol. (Herbal tea that contains no caffeine is OK.)  If you are out in the hot sun, beverages should be cool, but not too cold.   If you have epilepsy, kidney or liver disease, or are on a fluid-restricted diet, check with your physician before increasing liquid intake.

5.  Wear light-colored, loose clothing made of natural materials, such as cotton.  Wear a hat with a brim to keep the sun out of your eyes and off your face.

6.  If you engage in heavy physical work for a living, monitor your body weight.  If you lose more than 1.5% of your weight from sweating, you may be at higher risk for heat exhaustion or heat stroke.  As an example, if you weigh 150 pounds and lose more than 2.25 pounds from sweating, you need to be careful.

7.  Keep electric lights off or turned down low.  Stay in the shade, and stay on the lowest floor of your home.  Open windows during the coolest part of the day and close them when it gets hot. 

8.  If you don't have air conditioning, plan to spend time in air-conditioned areas, such as a shopping mall, public library, or movie theater.

9.  Take a cool bath or shower periodically, or cool down with wet towels.  Keep wet washcloths in the refrigerator or freezer (in plastic bags) to use when you need them.

10.  Avoid eating heavy meal, and avoid eating hot foods in warm weather.  Stick to light, regular meals.

11.  If you are on prescription medications, find out whether any of the medications has particular side effects in hot weather.

12.  Never leave a child or a pet in a car, even if the windows are rolled down, when the heat index is high. 

13.  Never leave a child or a pet sleeping outside in direct sunlight for any length of time when the heat index is high.  (Babies' skin can sunburn, even if the heat index is not that high.)

14.  Avoid walking your pet on blacktop surfaces in hot weather, as their paw pads will burn.

15.  Check on family and friends, especially elders, who spend time alone and do not have air conditioning.  

Stay cool!  :-)

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