Hydrate and stay cool to avoid heat illnesses

The National Weather Service reports. . . that among natural hazards, heat kills more Americans than lightning, hurricanes, tornadoes, floods or earthquakes. Winter's cold, a natural hazard also quite familiar to the state's rural community, is the only hazard causing more deaths.

Hard physical labor during periods of high heat and humidity are a given for Nebraska's farmers. While producers can't control the weather, often they can mediate its effects on their health by taking a few precautions.

"As much as you can, help your body become acclimated to the heat. That can help when we get to the hottest part of the summer," said Dr. Bob Muelleman, a University of Nebraska Medical Center professor and chief of the Nebraska Health System Section of Emergency Medicine.

Working up to a good sweat for an hour or two a day for 10-14 days can help your body become accustomed to the heat and initiate its own safety measures. The body will start sweating at a higher volume and at a lower temperature and will reabsorb its sodium, Muelleman said. Then when a heat wave hits, your body will be better prepared to deal with the extreme temperatures.

"The body is pretty good at maintaining a normal body temperature through evaporation of sweat," Muelleman said. On really hot days, with maximum exertion, you can sweat up to two quarts an hour. However, if it's too humid and the sweat can't evaporate, your body won't be able to cool down as well and there is an increased health risk.

"When people ask me if it's the heat or the humidity [making it uncomfortable], it's the humidity," Muelleman said. As the relative humidity increases, it feels warmer than the actual air temperature because you can't sweat and naturally cool your body.

Predicted air temperatures on weather reports can indicate a potential problem, but it's important to account for the humidity. To help people recognize when they may be more at risk of heat stress, the National Weather Service (NWS) now issues heat index warnings when the temperatures and humidity are expected to be high.

Calculating the heat index

To estimate the heat index in your area. . . use the calculator on the National Weather Service site at http://www.srh.noaa.gov/elp/wxcalc/heatindex.html

For example, the NWS heat index indicates that with an air temperature of 90^oF and a relative humidity of 40%, it will feel like it's 91^oF outside — not much of a difference. However, the same 90^oF temperature with a relative humidity of 75% will feel like 109^oF and put an individual at risk for heat stress. During periods of high heat and humidity, local weather stations often include predicted heat indexes in their forecasts so you can plan accordingly. If the heat index is 90-105° F, there is a risk of heat illness. When the heat index is 105-130°F, heat stroke is possible and if the heat index is over 130°F, heat stroke is likely.

Effects on the body

A person can develop a heat-related illness on any hot, humid day, given a variety of health and climate factors. When your body temperature rises, your body tries to compensate. Your heart starts beating faster, you breathe faster, and your blood vessels dilate to bring more blood closer to the surface to cool.

These physical changes that develop when working outside in the heat also can increase the risk of complications from other illnesses such as coronary artery disease, congestive heart failure, emphysema or asthma, and it can make it harder to control diabetes. Some individuals also will be at higher risk for heat illnesses or heat stroke, Muelleman said, if they're taking drugs which inhibit sweating. These might include antihistamines; drugs prescribed for some psychological illnesses, blood pressure medicines; or any stimulants or drugs that increase your metabolism. When in doubt, ask your pharmacist if any medications you're taking may affect your ability to sweat or be in the heat for an extended time.

Symptoms of heat illnesses

Heat-related illnesses range from fatigue and cramps to heat exhaustion and heat stroke.

• Cramps due to excessive sweating typically develop in the thigh muscles and indicate a deficiency of electrolytes. Taking in electrolytes through fruit or sports drinks can help alleviate this.
• Heat exhaustion symptoms include nausea, chills, dizziness and dehydration. Once you notice these symptoms, stop what you're doing and cool off. Apply wet rags to help your body cool.
• Heat stroke is much more serious. Symptoms include a lack of sweat, headache, rapid pulse, altered mental state, confusion, lethargy, seizures, and even unconsciousness and a body temperature over 101^oF.

If the body temperature isn't quickly lowered, heat stroke can be fatal, Muelleman said. If you suspect someone is suffering from heat stroke, seek medical help and take immediate action to start lowering his or her body temperature. While you wait for an ambulance, help the person into the shade or to a cool place, wet their bodies to increase evaporation and provide them with water.

While you can't control the heat and humidity, you can control your activity level. When you begin to notice the first signs of heat illness, reduce or stop activity, get in the shade, remove any excess clothing you can, apply cool cloths to help lower body temperature, drink fluids and take it easy. If children are helping you in the field, be sure to watch for warning signs and let them take a break and cool down when they need it. The first signs of heat exhaustion for children are when they become flushed, crabby, and don't feel well.

Drinking plain, old-fashioned water works well to replace fluids if you've been outside a couple hours, but if you've been sweating profusely for more than a few hours, you'll need to replace electrolytes too. Eat a banana, drink fruit juices, or drink a sports drink that provides electrolytes. You may need to replace up to two quarts of fluid for every hour spent in strenuous exercise. Avoid drinking alcohol or caffeinated beverages.