The Effects of Heat

Staying cool is a challenge during Mississippi summers but paying attention to your body's signals that it's becoming overheated is important. In this Health news segment, MPB’s Karen Brown spoke with Dr. Robert Allen Sheely, Jr. Baptist Health Systems in Flowood, about the dangers of heat related illnesses starting with the differences between them.

Dr. Sheely: You’ve got heat exposure which is brief. When you get fatigued and sweaty and you feel tired and very thirsty. And then you’ve got heat exhaustion which is a little worse. That’s where you have to go sit down and take some time out and then you have heat stroke and that’s when your core temperature goes up because you can no longer radiate heat or get rid of heat through sweating. You basically have sweated out all you can sweat and your core temperature basically goes up. And heat stroke can actually lead to very serious problems; the most serious would be what’s called Rhabdomyolysis which is muscle breakdown. If you get to the point where you can’t evaporate via sweating and radiate heat off of your body you get muscle breakdown and your urine will turn reddish like Kool-Aid. The problem with that is that Rhabdomyolysis can cause some electrolyte abnormalities as well as heat stroke because your potassium, chloride, sodium and so forth are all out of balance. The myoglobin which is a protein from your muscles will actually clog up the kidney. That can lead to renal failure. You may have to have dialysis.

Karen: Who’s most vulnerable to heat?

Dr. Sheely: The very young and the very old.

Karen: Why?

Dr. Sheely: As you age your skin thinks and your percentage of body fat goes up. Your ability to reclaim salt and water from your kidney goes down and your ability to sweat goes down. Basically, your physiology begins to fail. Your reserve and your physiology are very, very, very low.

Karen: Is there also an inability, as you age, to tell when you’re in trouble?

Dr. Sheely: That is also a problem. The, what are called “osmostats” in the brain which tell you “you’re thirsty so drink” don’t work as well, especially if you have organic brain syndrome or Alzheimer’s. A normal function of age is to have less hunger and less thirst. The very young are vulnerable because they’re smaller and their skin is thinner. They perspire harder and have less reserve.

Karen: If you’re outside for a long period of time what are they symptoms you’re going to feel that indicate you need to get out of the heat.

Dr. Sheely: Your heart rate will pick up, you’ll feel light headed. You’ll feel dizzy. You’ll get a headache, possibly nausea. You can get cramps. Most commonly you’ll get cramps in your calves or your abdominal wall … extreme thirst.

Karen: Let’s say you’re past that point and are no longer able to tell you’re in trouble. If you’re with someone who is exhibiting these symptoms and they suddenly stop sweating or they become quiet as well …

Dr. Sheely: Quiet, they obviously won’t be sweaty. They’ll be very hot. Predominantly this kind of thing is seen in football players who are brought into the ER. Basically, a lack of perspiration. The actual color is another variable. Typically you become more pale as your body tries to clamp down. In the emergency department we use cooling blankets and fans and chillers if someone’s core temperature is high and we also pump them full of fluids to get their kidneys functioning.

Karen: But if you’re outside and you can get them in water, would that be a good thing?

Dr. Sheely: Water is probably the best way because water absorbs heat as it goes from a liquid to a gas. Get them to drink more liquids and remove any heavy clothes and get their skin to where they can actually have evaporative cooling.

Karen: How much water should we be drinking if we’re going to be outside for an extended period of time?

Dr. Sheely: At least an 8 oz. glass of water every fifteen minutes when the temperature gets about 95 degrees. If you’re going to be out for longer than an hour, typically you need to start replacing electrolytes, sodium, potassium, chloride and also glucose. Sports drinks like Gatorade or PowerAde and that sort of stuff.

Karen: They’re actually preferable to drinking water?

Dr. Sheely: If you’re going to be outside actively working or exercising for more than an hour in high, ambient temperatures. Most people don’t feel like they need to drink that much liquid when they’re outside in the heat but you begin sweating within a few minutes of being outside in high heat. Probably the biggest mistake people make is not drinking enough and not listening to their own body’s thirst.