Home Forums Hunting & Shooting Hunter's Campfire Medical Realities of "Heat Illness"

One thing I noticed that has helped me a bunch with after exercise cramping is some stuff called "Sport Legs". It has calcium and magnesium salts of lactose, I think?
I did a 9 hour, 50 mile mountain bike ride last Saturday and I didn't have any cramps after the ride-normally I would be fighting cramps for a few days afterwards.

Good idea, Seafire. Since we instituted the before-and-after-practice weigh-ins with our student athletes and made it a rule they have to drink enough to replace half their weight loss, we've cut our heat illness incidence to dang near zero. We're 7 years into it now and have only had one case of heat illness since then. This includes football, soccer, cross-country, well over 250 athletes per year total each late summer/early fall.

We had a cross-country runner slip thru the cracks last week and she got pretty sick from it, but it was only because she "cheated" on the weigh-in sheet.

Pat Powell's recent experience with heat illness, and the various well-intended but sometimes wild-azzed suggestions for treating it, have prompted me to (for once) post a serious, non-tongue-in-cheek post about the medical realities of heat illness.

FYI, those who don't know, I'm an ER doc with a large side-practice in sports medicine, a member of the Am College of Sports Medicine, and Head Team Physician for a Div. III NCAA school. Heat illness used to be one of our biggest problems. Research and practical experience by a number of NCAA colleges and sports medicine researchers has put that to an end, for the most part.

"Heat illness" encompasses a group of terms, including heatstroke and heat exhaustion, neither of which is very specific and hence mostly useless, as well as encompassing the electrolyte disorders that may accompany exertion in a hot environment. It's simplest just to lay aside these terms and concentrate on the general concept that "heat illness" means body fluid and electrolyte imbalances brought on by our bodies' response to heat, or more often, response to exertion in heated conditions.

Here's the basic physiology: all the cells in the human body are bags of water with lots of dissolved electrolytes (ions). The two most important electrolytes are sodium and potassium, which are the essential ions for all muscular and neurological cell function. Other electrolytes such as calcium, magnesium, and phosphate are also important, but they don't fluctuate much in heat illness.

When you're hot, your body tries to cool off by sweating, by radiating heat from the skin, and by blowing heat off in exhaled air (primarily... there are other means). Sweating's the main thing. Sweat is basically water and sodium, so if you're sweating, guess what you need to replace? That's right, water and sodium. When you're exerting yourself in heat and sweating, you're also depleting glucose and glycogen stores as your metabolic rate rises to meet the demands. So you need to replace glucose, as well.

As long as you keep your water, sodium, and glucose reserves adequately replaced, you're very unlikely to experience heat illness. This is the most important single concept to hang on to.

However, if your water and sodium levels (and in endurance events, glucose) become depleted, your ability to cool yourself becomes exhausted very quickly, and your core body temperature will start to rise rapidly (especially with exertion). It's not uncommon for endurance athletes with heat illness to have core temperatures in excess of 108 degrees, and some athletes have survived core temperatures of over 110 degrees. When your body temp rises above 104 or so, you will experience symptoms that progress from flu-like inconvenience to truly life-threatening: weakness, lethargy, dizziness, feeling like you might pass out, confusion, loss of bowel/bladder control, ataxia (loss of coordination), coma, and, eventually, death. If you want to see video of what it's like, go to YouTube and do a search of marathon runners. This clips shows a fairly typical case of severe heat illness:
http://www.youtube.com/watch?v=8ceoSotrLpc&feature=related
Anyone remember that horrifying scene at the 1984 LA Olympics, with that female marathon runner staggering around the Coliseum while the whole world watched her dying, the commentators talking about her bravery and resolution, and no one making an effort to get her to treatment to save her brain and/or life? I can't find the clip, but if someone can, please post the link. It's truly horrifying, but truly educational as well.

Treatment of heat illness of any degree involves two things: first, restoring depleted water and electrolytes, and second, bringing the core body temperature down. For most Campfire members, the latter will likely never be necessary, but if you need to cool off, get into some cool water a.s.a.p. Get a rectal temp and if over 106 degrees get thee to a hospital.

Which brings us to the problem of fluid/electrolyte depletion and replacement. First, in the majority of fluid/electrolyte depletion cases, the problem started BEFORE the heat stress. Most people with heat illness are inadequately hydrated BEFORE they go out into the heat. So the best thing you can do for yourself prior to going out in the heat is make sure you're not dehydrated from drinking beer the night before, or from going out day after day in the heat and failing to replace your fluids and electrolytes before going back out into the heat. How do you do this? Easy. 1) Weigh yourself before you go out to work/play in the heat. 2) Weigh yourself when you come back in from working/playing in the heat. 3)Drink one Imperial pint (20 oz) of water or sports drink for every pound you lost in the heat, and don't go back out into the heat until you've replaced AT LEAST HALF of your weight loss.

But what if, like Pat, you're already hooped, loopy, and feeling like you've got a concussion from the heat? Well, you've now got fluid/electrolyte imbalances in the brain, and you aren't going to be able to correct that in a few hours. Most people with neurological symptoms due to heat illness can expect to have a recovery period much like a person who has sustained a concussion (2 to 7 days) because the biochemical changes in the brain due to heat illness are similar to those of concussion.

Treatment in this case involves lots and lots of balanced electrolyte solutions (Pedialyte, dilute Gatorade, Gookinade, etc) and REST in a cool A/C environment. Gatorade has more sugar than you need and Gookinade has slightly more potassium, but other than that there's not much to choose between them. (I'm not sure why Miss Lynn's doc got all pizzy about her drinking Gatorade, as it's a well-accepted sports drink in the sports med field and there's lots of research to show it's better than plain water.) In most cases IV fluids aren't needed, oral rehydration/replacement works just fine. But just because you've corrected your water/electrolyte problem in your bloodstream doesn't mean you've corrected it in your brain and muscles... that can take days, as I've noted above.

Better yet, try to avoid having to treat heat illness altogether: make sure you're staying hydrated/electrolyte-replaced while you're out in the heat. The simplest guideline is that if you're not peeing, you're not drinking enough. And if you're drinking straight water, make sure you're getting electrolytes from other sources (food, V8 juice, etc). Too much sweat without sodium replacement can lead to "water intoxication". Don't sweat the science, you really just have to drink electrolyte-replacing fluids.

Research shows people drink more fluids if the fluids are 1)cold, and 2)sweet. Hence the sugar in sports drinks... it encourages drinking, and provided you're not diabetic, you're not going to injure yourself by drinking a few grams more glucose than you normally would. My recommendations are, in order, Gookinaid, dilute Gatorade, and chuck the rest. Pedialyte is too expensive to use routinely, IMHO.

Personally, I use Gookinaid crystals mixed slightly dilute with ice in my Camelbak, or I mix up Gatorade half-strength the same way. One of my buddies freezes two quarts of Gatorade in his Camelbak the night before, then adds 2 quarts of full-strength Gatorade in the morning. Keeps it cool all day long. And BTW, a Camelbak or similar hydration pack is worth its weight in gold IMHO. I use mine every time I go to the range, at every class, and it's usually on my back at every sporting event I attend as a physician.

Hope that takes some of the mystery out of the heat illness deal.

Oh, and BTW, now that I've passed 3000 posts, my word has even MORE weight to it, doncha know? Just ask Isaac. He'll tell ya.