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The Hype of Dehydration and Heatstroke
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Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Re: Re: The Hype of Dehydration and Heatstroke on 04/09/2013 20:50:16 MDT Print View

I saw the difference first-hand when I was in Army training during the summer at Fort Polk, Louisiana (read: hot and humid). They picked a warm day for us to do our 15-mile road march. One guy collapsed around nine miles out. They dragged him off the road and into the shade, then rubbed his skin with cool water while they got him to drink more fluids. He was conscious, so they hauled him back to base. That was heat exhaustion. The second guy was too stubborn to quit, so he was going until about 12 miles out where he collapsed. They dragged him off the road and into the shade, but he was unconscious. His skin was hot and dry, so they were not able to revive him. Once he got to the hospital, he was revived, but he had some brain damage. That was heat stroke. Not good.

I think our goal here is to drink more fluids and maybe electrolytes so that we never collapse in the first place.

Too many hikers will try to cross the desert without carrying enough water (weight). You have to have the experience to know what works and what doesn't work.


Craig W.
(xnomanx) - F - M
Re: Re: Re: Re: Re: The Hype of Dehydration and Heatstroke on 04/09/2013 21:07:21 MDT Print View

"I think our goal here is to drink more fluids and maybe electrolytes so that we never collapse in the first place."

But that's the crux of it.

The entire premise of the article I linked is that heat stroke (and death from it) and dehydration do not necessarily correlate. Too many examples of people dying of "heat stroke" too early in an event or race to have been dehydrated. Nobody critically dehydrates in less than 5K, yet people die from "heat stroke" in the beginning miles of events on a regular basis.
In addition, there are plenty of cases of death and illness attributed to "heat stroke" that occur when it's not particularly hot and the victim was not exerting themselves very hard, thus leading to the question of how many of these supposed "heat stroke/dehydration" cases are actually due to some other issue.

This article is not arguing that heat stroke and dehydration do not exist; it's saying they are too loosely used to describe medical emergencies people are having that could have entirely different causes.

Dan Durston
(dandydan) - F

Dehydration & Heat stroke on 04/10/2013 13:20:10 MDT Print View

Great thread going here. This is something I've been meaning to get a better understanding of.

Perhaps someone can offer some insight/diagnosis on my situation last August. I planned a 1 night 60 miler that consisted of 15 miles one evening and then 45 miles the next day. The second day I hit the trail at 6am feeling good. It was a warm day and I was on a quick pace, so I sweating decently. I was trying to drink water, but I was probably falling behind. Then I got to an uphill forest fire burn area that offered little shade, which left me exposed to the mid day heat (full sun, 80 F) at the same time I ran out of water (poorly planned). This section was about 5 miles and I couldn't find my hat before the trip, so I felt like I was withering in the sun. I started to get a headache, which isn't that abnormal for me. I was sweating quite a bit - I remember marvelling at all the white sweat stains on my shirt and pack.

Anyways, in the late afternoon the headache remained and I started getting nauseous but forced down some water. All had been eating that day was energy bars and a tiny bit of jerky. I realized I was probably low on electrolytes so I finished the salty jerky, but it wasn't much. Even though the day cooled after dinner I still felt really hot and I was getting muscle cramps. My hands would clench and I couldn't release them - first time that had happened to me. By 5pm I really felt like crap: headache, nausea, overheating. I pushed on for a couple more hours and called it an early night (8pm) after ~35 miles. In camp I tried to sip water but I puked it up. The evening had cooled off but I was hot, so I laid naked in my tent with my heart racing. That was the weirdest part - my heart was probably up around 120 and it wouldn't slow down. I realized I could keep water down if I just had a wee bit and waited 20 minutes, so I worked on hydrating that way. I figured the biggest problem was maybe electrolytes, so I opened a foil pouch of tuna and drank only the salty brine (way too nauseous for food). I laid there barely sipping water from 8pm to probably 2am with my heart rate up for the first ~3-4 hours. The next morning I got up around 7am. I didn't feel so great, but I wanted to finish that last 10 miles before the heat of day.

So is this standard dehydration/low electrolytes? Or something else? For me the weirdest part was laying there while my heart was cruising along and refusing to come down. I heard that when you're low on water, heart rate can elevate to pump blood to help with cooling the body, so perhaps it was dehydration plus some overheating?

Edited by dandydan on 04/10/2013 14:21:10 MDT.

jeffrey armbruster
(book) - M

Locale: Northern California
"The Hype of Dehydration and Heatstroke" on 04/10/2013 14:01:22 MDT Print View

Dan: this past winter I went nordic skiing pretty hard for three days. Highish altitude, cold dry air and a stove in my cabin at night. On the fourth night I woke up at 1:30 with my heart racing and erratic. It didn't stop. I ended up in the ER and was cardioverted--electric shock to the heart, not fun--at which time I reverted to normal rhythm. Docs called it idiopathic, which means they don't know what caused it, but the best bet was dehydration. Very very scary.

So I just bought a steripen and will carry it along with a collapsible nalgene in my GG belly pack. This is to make it as easy as possible to drink water during the day during my hikes.

You don't want this to happen for a ton of reasons, but one more is that now there's a higher likelihood of recurrence. Also, apparently this sort of racing/atrial fibrillation (did you have that?)often onsets at night while you're sleeping.

It never occurred to me that I was overdoing things; in fact I felt great for the three days of skiing. But I live at sea level and ski at 7,000 feet. Age is catching up to me. Now I have to watch things.

Scary, no? I bet that you'll remember this and not do that hike again.

Craig W.
(xnomanx) - F - M
Re: "The Hype of Dehydration and Heatstroke" on 04/10/2013 14:14:17 MDT Print View

Both scary stories.
Jeffery, your experience is sort of what the article is talking about. The author raises the idea that many people are actually having some sort of cardiac event during exercise. Since the cause of the cardiac event is hard to pinpoint and could have to do with some existing pathology, a lazy answer is that it must have been due to dehydration or heatstroke, which both can present many of the same symptoms as a heart issue.
But if your bodyweight wasn't compared before and after the event and no actual tests on your fluids were done, how would anyone know that dehydration had anything to do with it beyond simple speculation?
Same goes for heatstroke; unless your core temperature is being monitored, most serious cardiac issues would present the same symptoms that heat stroke would.

But hey, I'm no doctor, (was a former working EMT with wilderness first aid training)
but I find it an interesting topic.

Sort of scary, because there have been many studies in recent years on endurance athletes and sudden cardiac issues or lasting damage supposedly done through endurance sports.

Dan Durston
(dandydan) - F

Cardiac on 04/10/2013 14:19:01 MDT Print View

Scary stuff indeed. My heart was fast but not erratic - so steady but alarmingly high while I laid there for hours. My guess was 120 BPM whereas I normally measure 55-65 at rest.

Edited by dandydan on 04/10/2013 14:22:45 MDT.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: "The Hype of Dehydration and Heatstroke" on 04/10/2013 14:30:54 MDT Print View

Many years ago I was leading a peak climb on skis. The group got up to the midway camping point during the first day, and the plan was to bag the summit early on the second day. That first evening we were sitting around eating dinner, and then we retired early to sleep before the 4 a.m. wakeup call. Late that night one of the crew came over to my tent to wake me up. His tentmate was having some sort of stress and could not sleep. I checked the guy out, and he had a fast pulse. His respiration was not shallow and rapid (which might point to hyperventilation), but in fact it was deep and rapid, and he had plenty of oxygen. There was not a great deal that I could do for him, so I gave him one pill, had him drink some water, and then try to sleep. That worked. At 4 a.m., the rest of us got up to prepare for the summit, and this guy decided to stay in camp, even though he felt better. We all left the mountain by the afternoon of the second day.

What was the pill? A salt tablet, perhaps as a placebo.

What was the ailment? Hard to say. Maybe an anxiety attack. Maybe dehydration. Maybe low electrolytes.


Paul McLaughlin
(paul) - MLife
Re: Dehydration & Heat stroke on 04/10/2013 16:54:04 MDT Print View

Dan, I can't diagnose what happened to you, but I can safely say that if I had done what you did while eating and drinking as you describe I would have felt like crap at best. Saltier food and more water would be my recipe for a better result - it's what I have done in the past in similar situations. Walking across the Grand Canyon in a day in midsummer, I drank all the water I could get(around 3 or 4 gallons) and ate a lot of salty peanuts. That worked out well. My feet were trashed by the end, but no ill effects from the extreme heat (110 at the river) and low humidity.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Dehydration & Heat stroke on 04/10/2013 17:00:47 MDT Print View

Hi Dan

> some insight/diagnosis on my situation last August.
I am NOT a medico, but ...

To me that sounds a bit like a combination of heat stress (not heat stroke) and a viral infection. I suspect that without the virus you might not have been affected at all.


Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: The Hype of Dehydration and Heatstroke on 04/10/2013 17:08:07 MDT Print View

A highly trained endurance athlete is a lot different than us mere mortal backpackers.

I agree that we focus too much on drinking water and to never, never feel the least bit thirsty.

Each individual is much, much different. A while back Craig and I did an all day hike through the desert. I consumed probably 1/2 the water he did and probably was less thirsty. At the time Craig was doing a lot of long distance running training and I am about 30 years older than him. My body just works differently, not to mention I am more attuned to water needs since I hike in deserts a lot. In addition Craig is bigger than me with lot more muscle. Neither of us were in any kind of danger or was water a problem, just want to point out that each body is different.

I normally stop to drink about once an hour, and sometimes longer between stops... even when it is hot. But I have a lot of experience hiking were water is a precious commodity and am acclimated to the conditions -- if there is such a thing a acclimation.

The other thing to consider is the ambient temperature. Anyone running a 5K in 90F temps is going to have a different experience than running it at 100F.

I remember Colin Fletcher posting a table showing how long a person could last with different amounts of water. At 120F during the day and only walking at night, the average person will die in 1 day with no water, 2 days with a quart of water. If they sat in the shade at 120F and did nothing to exert themselves, the average person will die in 2 days. Move the ambient temperature down to 70F and death occurs in 10 days for no movement and 7.5 days if hiking at night.

Almost every year people die from "heat stroke" where I live when it gets hot. Most of these die on day hikes on strenuous trails. Of course we don't know about any pre-existing conditions or their physical condition. There have been several Marines from the 29 Palms Marine base, where they do desert training, who have had to be rescued on the Skyline Trail here, when they have hiked less than 7 miles and ran out of water and became too ill to continue.

I guess the bottom line is that we need to know what the hell we are doing when hiking. Articles like this a good, but we need to be prepared.

jeffrey armbruster
(book) - M

Locale: Northern California
"The Hype of Dehydration and Heatstroke" on 04/10/2013 19:07:17 MDT Print View

Elevated heart rates will often revert to normal rhythm on their own. You really want this to happen. But think this through: someone like Dan, obviously young and fit, crashed his body to a point where his heart went crazy for many hours. This is a warning sign. If it happens to you, and your normal rhythm returns, you might want to take it easy for a couple of days.

Look, Dan's "one night sixty miler" without a hat in high temperatures and not enough water: that's extreme. This would be extreme--in my estimation-- even with the hat and water etc. I mean, I couldn't do it. Sometimes everything works right and you get away with pushing the envelope. But if you watch (or play) enough basketball, for example, you realize that the human body has peaks and valleys. Performance varies. Everyone on this forum has bonked for no apparent reason, etc. And you can't always predict things beforehand.

Sometimes mental determination overrides the body's needs and messages.

I used to think that I couldn't exert myself too hard; it was always healthy to push the limits. I'm backing off on that philosophy. But then I'm becoming an old guy.

p.s. they did instantly put me on fluids in the e.r. and say that I was dehydrated.

Edited by book on 04/10/2013 20:18:13 MDT.

Larry De La Briandais
(Hitech) - F

Locale: SF Bay Area
the link on 04/10/2013 21:18:40 MDT Print View

I always thought that the link was when you became dehydrated enough to stop sweating your temperature began to rise. If it got high enough then you could suffer heat stroke. Anyone know? And anyone know what heat stroke actually is?

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: the link on 04/10/2013 21:35:47 MDT Print View

Generally there is a maximum body temperature, maybe 106 F, and that is where irreversible brain damage occurs. Maybe it will be a little. Maybe a lot.


Michael Ray
(topshot) - MLife

Locale: Midwest
Re: The Hype of Dehydration and Heatstroke on 04/10/2013 21:53:35 MDT Print View

I wish the author explained more of what they found in the runner that kept gaining heat in the ice bath.

Fascinating subject since my son and I will be doing Grand Canyon and a little Death valley this summer. I don't recall noticing my sweating in dry desert heat though I suspect it's just because it evaporates so fast and the air temp negates the evaporative cooling effect. That was decades ago so maybe I don't recall correctly. I do remember having the windows down while driving felt like standing in front of a furnace duct. :)

Ian B.

Locale: PNW
Dunno on 04/10/2013 22:01:22 MDT Print View


Without being there to take your vitals over a period of time, and BP checks supine and standing, all I can offer is pure speculation.... And I'm not a Dr.

My first guess is hypovolemic shock exacerbated by hyponatremia/kalemia.

Second guess is SVT.

Third guess, all of the above.

Gregory Allen
(Gallen1119) - M

Locale: Golden, CO
Re: Re: the link, "Waterlogged" on 04/10/2013 22:01:23 MDT Print View

I'm reading Noakes book now and it is slow going with lots of detail and references. It is a VERY well documented and referenced book. I think the key is drinking when thirsty and not forcing water, or a "sports drink", past that point. It is very clear that ultra endurance athletes are much different than us mere mortal BPL-ers, but how much different I don't know...maybe not as much as we think. We do respond in a similar fashion to water loss, but the human body is well equipped to handle that water loss, elevated HR, and even some moderate elevated body core temperature and recover without untoward effects. Metabolic rate, or level of exertion, seems to be the key and not what has been hammered into our heads about hydration, electrolytes, etc over the last 30-40 years, is the key. The body will adjust itself with a fairly wide margin of safety. Even ER docs have been duped my the pseudoscience propagated by the market gurus on the payrolls of the sports drink and supplement companies. Pushing too far past what our bodies tell us is dangerous, but maybe not as dangerous as what we have been led to believe marketing and industry. Moderation, and doing what your body tells you, is key. Slow down when it tells you to slow down, and drink when it tells you rhat you are thirsty. Keeping it fueled with balanced nutrition is far more critical that some "cocktail" of electrolytes or excessive water.

Lynn Tramper
(retropump) - F

Locale: The Antipodes of La Coruna
Re: The Hype of Dehydration and Heatstroke on 04/10/2013 22:19:28 MDT Print View

Though I don't doubt the hype of heatstroke caused by dehydration, for me, even mild dehydration can cause a migraine. I am not alone in this. So I drink regularly, before I am actually thirsty, to prevent migraines. My migraine-free comfort has improved immeasurably since I have been using a hydration bladder instead of waiting until I stop to access a stream or bottle on my pack. We are all different!

just Justin Whitson
To Dan on 04/10/2013 23:26:15 MDT Print View

Dan, i'm not a doctor, nor professionally trained anything medical, but i have had a long time interest and research in diet, natural health, etc. because i was forced to treat myself due to a mysterious childhood condition. Necessity is the mother of invention, AND applied knowledge.

It sounds like possibly one contributing factor was you were consuming too much protein on too hot of days. The combination of energy bars, jerky, and tuna equals a lot of protein (depending on the energy bars, some seem to have a lot and others not so much). Protein requires a lot of water to digest, hence it can speed up and/or exacerbate dehydration.

Not only that, because it tends to be harder to digest in general, it generally raises your metabolism making you feel hotter, hence you will sweat more, internal temps may more easily become critical, etc. Plenty of trained, knowledgeable people have advised to limit your protein while very active on hot days and stick more to carbs. Save the proteins for when it's cooled down and you're more inactive.

Anyways, there may be more contributing factors than that which helped to create a perfect storm of body imbalance.

Dan Durston
(dandydan) - F

Protein on 04/11/2013 06:54:14 MDT Print View

I didn't actually eat the tuna - I just drank the liquid brine to get some salts into me. My jerky was pretty minimal too - not more than 2oz. I'm not sure how much protein was in the energy bars.

Rob E

Locale: Canada
Re Protein on 04/11/2013 07:53:17 MDT Print View


I'm no doctor, nutritionist, or anything like that, just my own experience with endurance sports, but here is my take: I would suspect a combination of dehydration, electrolyte imbalance, and not enough calories getting digested properly (note, not eaten, but digested and absorbed). I've had almost identical symptoms quite a few times in the past. The last time I experienced it was a few years ago training in the heat for an ironman distance triathlon. For me the trigger is some dehydration, plus the wrong combination of foods, then trying to push through it basically shutting my body down eventually: bad headache, nausea, overheating, waves of chills, cold sweats, elevated heart rate, inability to sleep.

To cover that distance in those conditions, the speed, trail time required with the heat, you have strayed from the hiking to an intensity that would be an endurance sport. Hang around the finish line at any all-day endurance event and you'll see a lot of similar symptoms to what you describe. At higher intensities, a little bit of dehydration, or the wrong combination of foods shuts down their digestive system, they can keep eating, but things aren't getting digested, glycogen stores get burned up, blood sugar drops, dehydration kicks in and the results can be nasty.

Endurance sport forums have many posts from people who are very physically fit and well trained, but are wondering what the heck happened to them when they pushed themselves further/farther/faster in tough conditions and they basically shut down. The lesson on those forums is that muscular endurance and fitness is only one aspect of the training, and that nutrition is critically important and is an aspect of endurance sports that must be trained and dialed in as well. Basically everyone has to experiment in exerting themselves all day in tough conditions and find the right combination of foods and fluids that works for them. I know this forum can think of gatorade, gels and other sports nutrition as simply marketing hype, but in tough conditions at higher intensities, the stuff really works well, at least for me, but it took over a year to fully dial in my nutrition plan to find the combination products, intake rates and timing that really worked for me.

I will say though, pretty impressive mileage in tough conditions to gut it out like that.

Edited by eatSleepFish on 04/11/2013 07:55:30 MDT.