Department of Family Medicine
Heat Illness: Ten Questions and Answers
Heat Stress Index
-- Apparent Temperature Chart --
This table shows how relative humidity and temperature interact. For example, on a day when the air temperature is 90 degrees Fahrenheit and the humidity is 70%, your body reacts to an apparent temperature of 106 degrees F.
*Conditions of 113 degrees Fahrenheit or more signal danger of heat stress..
WHY IS HEAT ILLNESS IMPORTANT?
It can result in heart attack, stroke or death. Its effects are very subtle and difficult to detect by the person who is experiencing the gradual stages of early heat illness.
WHEN DOES HEAT ILLNESS OCCUR?
It occurs under conditions of high humidity and temperature. See the "heat stress index" table.
WHY IS HUMIDITY SO HARMFUL?
It blocks one of the major body defenses against heat illness -- the ability to perspire and evaporate moisture from the body surface.
ARE SOME PEOPLE "IMMUNE" TO HEAT ILLNESS?
No one is immune, but healthy, conditioned outdoor workers such as farmers, laborers, utility workers or athletes who are dressed appropriately (loose, porous clothing), who are well-nourished, well-hydrated, well-rested, and who take frequent work breaks will tolerate heat better than others.
WHO IS AT SPECIAL RISK?
Anyone with heart or lung problems, diabetes, obesity, history of previous heat illness, cardiac arrhythmia, neurological problems including stroke, cystic fibrosis, late pregnancy or the very young or old person is at special risk.
WHO ELSE IS AT SPECIAL RISK?
Persons who are young, conditioned and overconfident. These people tend to push the limits of human endurance. The heart, kidneys, adrenal, sweat glands, muscles, metabolism, and brain are easily overwhelmed by continuous heavy work under conditions of high heat and humidity.
WHAT ARE THE WARNING SIGNS OF HEAT ILLNESS?
Cramping of the muscles in the arms and legs or abdominal muscles is an early sign of heat illness. Heat cramps are helpful because they force a person to stop and rest. Muscle massage, rest and replacement of lost body fluids will relieve cramps.
WHY DO SOME PEOPLE FAINT OR LOSE CONSCIOUSNESS?
Heat exhaustion or heat collapse is a result of a sudden drop in blood pressure. The skin will be clammy from perspiration. The person will feel weak and may experience fainting. The body temperature will be normal or slightly elevated. The symptoms are due to dehydration. The victim should be moved to a cooler area or into air conditioning. Loosen or remove clothing and bathe in cool water. If the victim is conscious, give fluids such as a glass of water in which a half teaspoon of salt or baking soda has been dissolved. If a rapid improvement is not observed, seek medical assistance.
CAN A PERSON DIE OF HEAT STROKE?
Heat stroke (also called sun stroke) is a medical emergency. Death may occur. The body temperature climbs to 105°F or higher and the skin is flushed and red. Sweating has usually stopped and the victim is often unconscious. The body can no longer control its temperature. The victim requires emergency treatment with rapid body cooling, fluids for shock and CPR if breathing has stopped. The victim should be transported to the nearest medical care facility. While awaiting transport, cool the body with running water, wet cloths or ice packs. Do not force fluids if the victim is unconscious.
CAN HEAT ILLNESS AFFECT A WORKER ON THE JOB?
Operating machinery, power tools or farm equipment requires coordination, quick reflexes and good judgment to prevent injury. Early stages of heat illness together with fatigue can rob workers of normal brain oxygen. This reduces the ability to think clearly and increases the risk of on-the-job injury.
Six Steps for Prevention
Heat illness is much easier to prevent than to treat, but it takes time and preparation.
Step I: Respect the heat
Plan a work schedule that starts early in the cooler part of the day. Allow yourself frequent short breaks for cooling and thirst quenching.
Step II: Drink one third more liquids than your thirst dictates
Strong tea, coffee or colas may provide too much caffeine and cause frequent urination. Natural juices, milk, soups, diluted thirst-quenchers (mixed half with water) and frequent small sips of water will do the job. One sign of dehydration is dark urine in small amounts. An adequate intake of fluids keeps the urine light colored.
Step III: Nutrition
A well-balanced diet supplies essential protein, calories, vitamins, and minerals for muscle wear and tear. Crash dieting in the summer may be a one-way ticket to the emergency room. Small, frequent meals with plenty of fresh fruits, vegetables, dairy products and poultry will result in safe potassium levels for heart and muscle activity. Salt tablets are no substitute for a balanced diet; they may damage the delicate stomach lining and cause cramps. A handful of raisins has more energy and minerals than a salt tablet or a quart of thirst quencher.
Step IV: Protective clothing
A light-colored loose long-sleeved shirt and trousers reduce solar burn. A wide brim, open-weave hat will help to keep the entire head cool.
Step V: Look for early signs and symptoms of heat illness
Headaches, dizziness, confusion, slowed speech or reflexes, unusual irritability, lack of concentration, hot dry skin or lips, and dark concentrated urine are all early warning signs.
Step VI: STOP, REST AND COOL OFF
If any of the early signs develop, don't take any chances! Learn to respect the heat and live with it. Remember it takes two weeks for the body to become conditioned to periods of high temperature and humidity. No one is immune to heat illness.