Interesting observations from 70.3 medical tent re: sodium (Page 3)

From a medical standpoint, you want something that's iso-osmolar or a bit hypo relative to your blood, containing roughly equal parts glucose and sodium, with potassium and chloride thrown in there, with a few others like citrate etc.  That's actually the standard set by the WHO for oral rehydration therapy in terms of content.  Note this kind of formulation is studied within the context of treating diarrhea (aka from Cholera) and not endurance sports.  But the physiology behind why is the starting point for every sports drink manufacturer.

As a general comment, it's actually pretty hard to become hyponaturemic. Pretty much every other electrolyte needs to be out of wack before you start affecting your blood sodium levels.  The exception being severe hyperglycemia (ex diabetics), which can cause a pseudohyponatremia (the sodium is actually hiding in your cells because of the high glucose levels), but you're not sodium deplete.  Granted you have bigger issues to worry about if you're hyperglycemic to that extent anyways.  As mentioned before, you're homeostatic systems pretty much need to be shutting down to get seriously hyponaturemic.

edit: I should probably add that a lot of this might go completely out the window for a long, long IM given the stress it's putting on your body, but I'm still not surprised at the numbers cited earlier for natremia.  Last year volunteering similarly for our city's marathon, hyponatremia was never an issue.

This can be an extremely dangerous line of thought in warm conditions. Read AdventureBear's post above. It's an effort to stay hydrated when it's warm.

I'm getting out of my league here, but it's hard to go hyponatremic at rest. During exercise it's a little different, but your comments are similar to this doc:

http://www.rice.edu/~jenky/sports/hyponatremia.html

note what the former top kona doc says at the bottom...

"Dr. Doug Hiller's experience and observations on triathletes at the Ironman in Hawaii have shown that most hyponatremic athletes in this hot climate are both dehydrated and hyponatremic. Thus, fluid restriction is really not a practical consideration.

Increased salt ingestion is the most prudent course. As long as there is not a medical reason to restrict sodium intake, then increasing your salt intake is perfectly safe. If you consume more sodium than your body needs, then your kidneys simply dump the excess.

In summary, eating salty foods, is a very safe, effective treatment and preventive strategy for exercise associated hyponatremia."

I raced yesterday in galveston and here was my nutrition plan and I pr'd by a large margin.  I had ZERO problems....

starting Friday morning I went on into hyperhydration mode.  I drank from sun up through the night at a ration of 2 24ounce bottles of water to 1 24 ounce bottle of Accelerade Hydro with base performance mineral salts (3 scoops) each drink.  ( I was peeing about every hour)

drove to Galveston Friday afternoon with the wife....continued the above protocol.  went out to dinner and stayed in the room the entire night sipping on my drinks or as we started referring to it as "sippin on some medicine" or my "purple drank".

woke up Saturday and 1 cup of coffee and ate breakfast and started on the drink protocol again. I ran 2 miles (easy) and swam 500 meters in the ocean.....that was the only time I spent outside...from my balcony I could see racers running...walking on the beach and my favorite sitting out at the pool all day. I rode my bike from the hotel (San Luis) to the expo to check it in and then my wife picked me up and we went to dinner. I was in bed by 9:30pm 

woke up at 5 and started drinking my pre race drink which is Pedialyte. I drank 24 ounces of Pedialyte and 48 ounces of water by the time I hit the water. I ate two gluten free waffles (not celiac but gluten makes me feel bloated) with peanut butter and ate two cups (packages) of gerber baby food bananas. I took 1 gu in 20 min. before the swim.

after exiting the mosh pit...i mean water. I jumped on the bike which I had a 24 ounce water bottle in the aero bars and a speedfil with Energylabs Execute. 4 scoops for 40 ounces with 6 scoops of base performance mineral salts.

on the bike course I drank 1 bottle of water (24 oz) between each aid station along with roughly 10oz of my speedfil between them.  I never waited till I was thirsty. I just drank. I also took in 3 gu's at mile 20, 35 and 50.

When I got off the bike I hit the run and felt great. no issues except hammies were a little tight in first 2 miles but went away quick.  on the course for the first 8 miles I drank at each aid station 1 perform and 2 waters...I also grabbed ice or sponges and put in my top over my heart or in my crotch ( so much so that my wife asked when I was done if I was happy to see her or just glad to be done racing..hahahah)...the last 5 miles I went to straight coke. I never cramped once or ever walked at all during the entire run. 

This post wasn't meant to brag but to say I think way to many people don't pay enough attention to PRE RACE hydration and pre race activity and the humidity. also I thought people were walking around pre race WAY to long in their wetsuits before they went in the water.. Granted I am coached by someone who has more experience in this type of racing at these distances than anyone on here....except for himself. He knows who he is and you would too. I will let him out himself.

As or the post about it being in the "mid 80s only"....heat index was over 90 and the "wind" felt like a blowdryer in your face..especially near hope road and on the runway..

as for the high Potassium...it could be from all the bananas they had on the race course and people were shoveling them in I guess. I never had a gu or fruit on the course stayed strictly to liquids.

hope this helps anyone as it did me and I raced great...I was fine when I was done and am today (except for the broken middle toe I have from kicking that stupid ramp they had coming out of the water and tripping me)

Almost all medical professional will disagree with you on this. There is no value to hyper-hydrating. Yes, there is danger in under-hydrating on a hot day, so you should not wait until you're parched, and if you really are sweating, start drinking before you're really thirsty. However, again, thirst is one of our most powerful drives and is the best indicator you have for your hydration status. Forced drinking while not thristy led directly to that hyponatremia scare in marathons a few years back when slow athletes kept drinking even when they weren't thristy - several cautions were promptly issued from medical associations to NOT do this and to go by thirst. 

I'll be we are on the same page in practice - if it's hot and humid out, you better believe I'll be aggressively hydrating even if I'm not thirsty (but fully expect to be.) However, there's no way I'll continue hyperhydrating in low-swewat conditions. 

Interesting information, Luke--thank you for volunteering and posting your observations here!

I also am not surprised, although I am wondering about seeing a lot of acute renal failure--was that a determination made from observed high BUN and creatinine?

I, too, see the irony but I still want to know about the acute renal failure!

On a very subjective and somewhat side note ... apparently quite a few people made it into the med tent with hypothermia at IM Melbourne. Since I found myself with a couple hours to diddle around in there, I had some good chats with the med tent head (a physician), a nurse, and two paramedics. All of them were of the opinion (no cool electrolyte/blood level testing machines) that of the ones who came in with hypothermia, many (including myself) were also dehydrated* beyond what would be normal for even as long as some of us were out there, and that contributed to the hypothermia.

Makes sense to me; any other opinions out there?

*I'm quite sure this was indeed true for me as it is very hard to suck up liquids (from an aerobottle) with frozen lips, and though I was trying to take hits off my downtube bottle, those are very hard to handle with numb hands ...

No one really wanted to answer the renal failure and high potassium, since most of the talk was about salt. But they are all linked and make perfect sense.  So here it goes:

First, the dehydration was due to isotonic fluid deficit.  Basically, the salt and the water levels remain an isotonic solution, where neither salt nor water is out of whack individually, but both are low together.  Water follows salt, so it makes sense both would be low.  If you just took in salt, you still won't correct the problem unless you take in water with it.  That way, you can have a temporary isotonic fluid excess, thereby balancing out the deficit and getting normal fluid levels. 

Second, the acute renal failure and hyperkalemia (extra potassium) are linked.  Acute Renal Failure has 3 different classifications: Pre renal, intra renal, or post renal.  Post renal acute failure is due to a blockage downstream from the kidneys, like a kidney stone jamming up the urethra.  And Intra renal is due to necrosis of the kidney cells.  But this is usually drug induced or due to ischemia.  I doubt this is the case with athletes.  Also, you would see a salt imbalance since the kidney cells aren't working and the salt is getting excreted, not maintained.  So the problem is Pre renal acute kidney failure. 

Pre renal is due to a few different causes which decrease the rate that the kidney filters blood.  These can be: chronic heart failure, shock, hypotension, and hypovolemia.  All attack the filtration rate of the kidney by decreasing it.  The first three listed, are likely not the causes at the race.  But since everyone was dehydrated, they were experiencing hypovolemia, a lack of blood volume due to isotonic fluid deficits.  The kidney will try to correct this by keeping in salt so the filtration rate can get back to normal (water follows salt, so more salt, more water, more water in blood means the blood volume can get to normal, and the kidney can have the normal fluid volumes to filter).  Salt levels remained normal since the kidneys were definitely not excreting it. But the people still did not take in enough water, so the hypovolemia created a lack of filtration by the kidneys, creating the renal failure.

Hyperkalemia was due to the pre renal acute kidney failure.  When the body undergoes kidney failure, like it was in these people's cases, it will undergo a process called the Renin-Angiotensin-aldosterone system.  You can google how it works, but basically its a hormonal process to maintain proper blood fluid volumes, blood pressure, and kidney filtration rates by keeping in salt, keeping in water, and constricting blood vessels..  However, with this system, potassium is expelled.  The cells are being hit with hormones telling them to release potassium.  The potassium is supposed to be excreted by the kidneys.  However, since the blood volume is low, the kidneys are not filtering, which means they aren't excreting anything. Potassium is staying in the blood creating the hyperkalemia. 

To compound this, if the people didn't train enough, or if they pushed it harder than they should have, they could have created a temporary hydrogen imbalance as well.  CO2 levels and hydrogen are linked, so an increase in CO2 in the blood means an increase in hydrogen levels.  An increase in hydrogen ions creates acidosis, which is pretty bad news and will shut down the body pretty quickly. To compensate, the the body uses respiration and cellular ion shifts for a quick fix.  You will breath quicker (to get rid of CO2, thus hydrogen) and the cells will absorb hydrogen ions so they aren't all pooled around in the blood to cause acidosis.  Hydrogen ions though replace potassium ions in cells.  The potassium is released into the blood, thereby creating hyperkalemia as well. 

Hopefully this has explained it in a way that makes sense. 

For all the doubters who apparently think I'm just making up this recommendation by MDs regarding the value of drinking to thirst for endurance sports:

"A group of experts in this condition has issued a number of papers and recommendations, including an international consensus statement on this disorder published in the Clinical Journal of Sports Medicine in 2005. Joseph Verbalis, M.D., Professor and Interim Chair of the Department of Medicine at Georgetown University Medical Center and a member of this group, recently updated the scientific community on the causes of this disorder in the May issue ofSports Medicine. "

The hyponatremia consensus panel has recommended that everyone, including endurance exercisers, should "drink to thirst" " that is, drink only when you feel you need to. Verbalis acknowledges that this advice is controversial, because some trainers and sports physiologists contend that "by the time you're actually thirsty, you have lost enough fluid to already be dehydrated, so they say you need to drink in anticipation of becoming dehydrated. 

"We dispute that notion, and contend that thirst is a good indicator of your body's need for fluids, and that there is a window of time over which you can rehydrate safely," he says. While a person "needs to lose about 1-2 percent of body water before thirst will reliably remind you to drink, losing that little is not sufficient to cause any significant health problems," Verbalis says. "Many of us are often dehydrated to such small degrees, and it does not significantly affect us."

Source: http://www.medicalnewstoday.com/releases/74522.php

(No, it's not the actual science article itself, but it's a summary of the consensus findings.)

Given that this is a CONSENSUS statement, it's pretty good as a recommendation to be followed by most doctors. Thirst is pretty good. 

FOr more reading with scientifically backed statements from the MD field, do a google serach on "drinking to thirst endurance training" or something similar, and there are a lot of similar discussions, from MDs that recommend the same, also from more recent dates.

Wow that is an insane amount of liquid.  I would not do that.  I also raced there and I just drank like I normally do.  All water until race day.  I had one bottle of triple mix Heed on the bike, everything else was water.  I had no cramping either.  Not even a hint.  I am not saying what you did was wrong, clearly it worked for you.  And I do agree that folks neglect their pre-race hydration.  But those are the same people who neglect their hydration all the time. 

I should clarify that the pre race drinking of liquids was not like I just sat and drank and drank and drank.....I just always had a bottle in my hand sipping on it all day..I think I took in close to 300oz each day Friday and Saturday. a little over 2 gallons a day for two days.

So what does a newbie do with all this? I've been training for 3 months now, logged quite a few miles (at least for me). Now I am completely convinced that I DO NOT want acute renal failure or any of the other "hypo/hyper-osis" stuff. 

(Btw-did major in exercise science as an undergrad, did enjoy reading the science behind all this, and "mostly" understood it.)

#confused

This describes me as well.  While I've never actually figured out what my sweat rate is, I can tell you that if I'm not very deliberate about taking in fluids I simply won't do it because I just don't feel thirsty. 

Earlier this year I was having heart palpitations and after a visit with the doc and some detailed discussions it become obvious I was dehydrated.  But I never felt thirsty....

I've also been told the efficiency of our thirst mechanism declines as we age.  No idea if that is true or not though...

That really is what the training is for in terms of also practicing nutrition/hydration strategies during. Starting points can be drinking at thirst and a gel or equivalent calories (these are usually taken with water as well, unless it's already a drink like Gatorade) every hour for stuff over an hour. Chances are that once you start going long (whatever that means to you, 2-3 hour rides or runs for example) you'll have a session where things do not go well or do not work or did not work in terms of eating/drinking, and that's where you start making adjustments.

Most can't. It's easy to say "weigh yourself before and then after exercise to determine", and while that works fine in a controlled environment, it doesn't really offer much in the real world. If you live in Canada and determine your sweat rate in the fall, then go race Ironman Cozumel (a late November race) your sweat rate won't even be close, and you will visit a Mexican hospital if you follow that hydration plan. Same goes for me if I went up and did IM Wisconsin. I would over drink if I relied on my Houston sweat rate. The reality is that your sweat rate will change daily based on heat, humidity, heat acclimation, hydration levels, etc. Not to mention that you lose a decent amount of fluid just by exhaling. That's why experimentation is so important when you train.

Take this site and others with a grain of salt (pardon the pun) or a biased eye. The advice someone gives from a northern climate will vary from what someone from a very hot and humid climate like myself give. Both might be right.

I agree with you. Sweat rate is not an exact measure and should not be calculated from 1 sample. Nor should it be the only criteria used for figuring out fluids.

I do a spot check now and then, different times of the year, treadmill, outdoor....it gives me a rough idea. I only check it on long workouts.