Hyperthermia Injury
-----Original Message----- From: "Bill Vickers, M.D."
Date: Thu, 17 Jul 2008 22:07:48 Subject: Hyperthermia Injury
To: William Vickers
This weblog started a few years ago with the idea of fostering the development of individual health thru exercise. Over the years, it has become more oriented toward sponsors and team adventure racing. Hopefully, it will get back to it's grassroots ideology as I take a step back from active adventure racing.
The first topic I figure is pertinent to this time of year, since just this weekend, I witnessed several participants, including myself, having symptoms of hyperthermia. The main reason I bring it up, is that it can be a rapid and fatal condition. Luckily, it is relatively rare, but it is more common than we know. Every year, athletes and normal people die of hyperthermia.
Unlike hypothermia, hyperthermia can be life threatening in only a matter of 15 minutes. Kind of a bummer.
Case in point. Some 12-13 yrs ago, I did the liberty state park sprint triathlon. It was a 90 deg day, not so bad, but we recently had a storm front passage, bringing with it humidity of 90%. The heat index that day was killer. A large percentage of the participants succumbed to heat stress. One, had severe heat stroke.
For myself, I was actually acclimated to the heat on that day, spending a better part of 2-3 weeks outside running. So, I was ok. However, I usually have trouble in heat when not acclimated. One advantage I have for long events, is that I have a low sweat rate. So, it works well when going long, but I have to be careful if I'm not acclimated. Sweating is very important for cooling. Vice versa, humidity and damp conditions are very much responsible for body temperature elevation, since evaporative cooling is very important. So, those excessive sweaters out there are ahead of the game, unless they forget to keep up with that loss. Luckily, we can all up regulate our sweat glands, with a little training. Just two weeks of short training sessions in 80-90 deg temps can help, if your careful in your exposure. Even mild heat exhaustion from training can be a set back in training.
Back to that triathlon. As usual, triathlon TA's are sometimes near a large body of water, partly contributing to the extra humidity. That triathlon, turned out to be a very memorable day. One, there was quite a bit of personal suffering with that heat index. Also, I had finished 2nd overall and 2nd in age group, making it memorable, mostly since I had a good bike split, breaking the old course record. Something I will always remember. (This was years ago, obviously).
However, what was most memorable, was the events at the finish. Only 10 meters from the finish, I witnessed a guy having what looked like a seizure. I took my timing chip (believe that was the first race that had those) and threw it to the volunteer, actually never crossing the line. The guy who collapsed happened to be right on the finish line. He nearly made it. I had to later contest my finish position, hours later.
At first, I was unsure what was wrong with the guy. So were the EMT's and volunteers who had stepped in. But it became clear he was having bonafide seizure activity and vomiting. He was a serious risk for pulmonary aspiration, since he was unconcious. His pulse was barely palpable. We got the fella in an ambulance and placed him on a monitor. The EMT's thought he was having a heart attack, since he was pale, unconscious, had dry skin, and had an abnormal ECG tracing. To me, it was memorable, since knowing his diagnosis saved his life. He was actually having hyperkalemia (high potassium) induced heart arrthymia. Which is treatable if caught early. At the time, I had a NJ medical license, and after some serious insisting, I was able to accompany him to the hospital, placing intravenous lines and working on stabilizing his airway from aspiration. And EMT ambulance (different than paramedics in those days), has little treatment options, and we couldn't control the heart problem till at the hospital. At that time, the ambulance folks were not certified to place intravenous lines either. He ended up having a temperature of 106 (after some initial cooling by us in the ambulance) and went into renal failure from cellular breakdown. (Called rhabdomyolysis). Not that it is pertinent, but it was the strangest thing being in an ER playing doctor but wearing a triathlon unitard. The ridiculous part of it didn't hit me until I was asked to leave and the ER doctors took over, everyone looking at me strangely in that outfit.
About three weeks later, I got a call from this guy wife, thanking me for saving his life. What I learned was, he was in intensive care for one week, and on dialysis for nearly that. He and some buddies had signed up for the race after a late night drinking challenge. Got to love those... He apparently was way out of shape, weighed about 210 #'s at the time, and doesn't remember ever doing the run part, but was feeling very heat exhausted getting off the bike. I told him and her, what impressed me most, was the fact that he ran that whole 5K, apparently unconscious the whole way. He was one tough dude. He nearly ran himself to death. At least ran himself to the point of seizures, arthymias, and renal failure.
This is in some way similar to the story of the one and only guy who defeated Chris Eatough at the World Championship 24hr MTB race, 2-3 yrs ago. He went into renal failure from the stress. Physiologically, it had to be heat related.
Triathlon specifically has a high risk of heat related injuries. After being on the bike, the body temperature is usually kept reasonable. However, after a TA and commencement of the run, the sudden lack of wind induced evaporative cooling, starts rearing it's ugly head. Nowadays, most triathlons handle this somewhat well thru some guidance of the usat guidance board and medical support. Cooling spray showers are frequently seen on courses nowadays. Sometimes even after the bike. My witnessing one participant of heat stroke, was only one event. It's actually quiet common, although not always so severe. In my race, the race director did not want to mention it to the other racers. Which became an issue since we took him to the hospital as a John Doe. After arriving back at the race, some 2 hrs later, I had to plead with the race director to make an announcement, to see if any of John Doe's buddies, had his gear and his wallet, to ID him. As usual, postrace, no one ever knew that a participant nearly died. What I know from ER colleagues, is that this happens more often than most people admit. Not exposing some coverup, it's just that even the race directors don't know what happens to the participants after being whisked away to an ER.
A few years ago, we had a hot and humidity Annapolis 10 miler, and a well known neonatologist died during the race. Since he was a local well respected physician, it didn't go unnoticed, and the race was forced to make some changes, including the start time and on hand medical personnel, including many members of my group who now volunteer. .
Alot of us also remember the famous Chicago Marathon of last year, where an estimated 100+ participants had to be driven by ambulance to a hospital. No one ever published a death rate, but after the first death, the race was cancelled. Although that is unverified. Or so the untold story goes. Essentially, the city wasn't able to handle the potential and increasing incidence of hyperthermia in participants at all the local hospitals, so, the race was stopped. It was all from a high heat index. In other words, hyperthermia can be serious.
Hyperthermia can be broken down into heat exhaustion and heat stroke, but simply, exhaustion is just a milder form of symptomatology. Actual heat stroke is usually when organ damage is ensuing. Not good when ya get there.
Symptoms are fairly simple. We have all experienced it in mild forms.. Feeling hot (no duh), nausea and vomiting, headache, dizziness. As heat stress takes it's toll, it can escalate rapidly if the heat index is high. Vomiting, dry skin, worsening headache, unconscious, cellular and muscular breakdown, and brain injury. High potassium leading to arrhythmias and death are the end of the spectrum. Hopefully you have gotten help before then. That's why John Doe was very lucky to survive. Kidney damage occurs from the breakdown products of cells, essentially plugging up the kidney filtration units. IV fluids are thus the mainstay of treatment, the earlier the better to help flush the kidneys, in nonmedical terms. The real risk, is that mild heat exhaustion can rapidly convert to heat stroke. Luckily, for most of us, we are not going too hard, and the body just collapses, hopefully cooling us off.
So, prevention is the key and some common sense. Heat acclimation is very important. Most of us all can upregulate our sweating capacity. On race day, staying hydrated and at a comfortable pace, is very important. Of note, once heat stress has started, the GI system is usually ineffective at that point. You usually have to "stand down" and let your body cool off, so the body and gut can begin absorbing fluids. Excessive heat stress essentially shunts blood elsewhere than the gut, making absorption poor. If severe symtoms become evident, seek medical help quickly. Cool the victim by placing cold water and ice on them. Ice in the groin, armpits, and neck area, help cool quicker. Do not have them drink if nearly unconscious. Consider the ABC's of airway, breathing, and circulation, until help arrives. Medically, IV therapy and various forms of advanced cooling exist. Lab tests for renal function, cell count, and electrolytes are important.
Anyhow, we all have done races where we could push harder. Being over heated is sometimes normal. However, just beware on those hot days with high humidity, if your not acclimated and slightly over weight.
Which leads to one petty annoyance of mine. Several years ago, while attending a medical seminar for the Ironman Lake Placid, it was commented on that many elite ironman triathletes were using very high doses of ibuprofen. Often up to 2000 mg of motrin before and during the race. Yikes! The theory from some misinformed coaches was that high doses will "thin the blood", keep them cooler, and increase micro circulation. Not a bad idea, but the theory is not substantiated. Even if there is a benefit, it's very mild. However, appropriate doses are ok to take. The decreased in pain thru reduced inflammation is an important aspect of ibuprofen consumption. Any endurance racer knows the important antiinflammatory effect of motrin and how it can help mentally. A better dose, that many elite endurance paddlers and runners take, is 200 mg motrin every 6 hours. Be careful though if you are having signs of heat stress.
The issue at heart, is that intense endurance racing, carries with it some mild forms of rhabdomyolysis from muscle trauma. Normal and hydrated kidneys have no problem handling that stress. However, motrin in higher doses, is nephrotoxic (bad to the kidneys). If you add on mild heat stress, more rhabdomyolysis, dehydration, and lots of motrin on top of it, you are only asking for permanent kidney damage. Unlike the liver, the kidney can not effectively repair itself. Luckily, we can live on 10-20% kidney function, but that make come to haunt you later in life.
In other words, don't take excessive motrin on a hot and humid day and go racing hard. .
Don't take this to mean that we shouldn't do endurance sports. In my book, the longer the better, and the more suffering, the more virtues. Just do it carefully on high heat index days.
If your interested in more reading on hot weather training, there are a few worthy articles at Chris Kostman's www.badwater.com, giving some tips from previous Badwater Ultramarathon participants.
