The Rim-to-Rim-to-Rim trip thread was getting contenous regarding possible mechanisms of developing hyponatermia which is low sodium levels in one's blood serum.

I posed some questions about hyponatremia to a double-board-certified, American College of Physicans member, hospitalist/internist M.D. (who I met on a backpacking trip in 1993 and married in 1997).

Summary of our discussion:

How could an extreme hiker/runner get hyponatermia?

Short Answer: By drinking far too much water.

But the kidneys are very good at maintaining sodium levels in a tight range with greatly varying hydration levels. Yes, you can drink so much water that in absence of any salt intake, you could flush your kidneys of sodium which would in turn deplete your blood serum of sodium.

She then went on to list numerous medical conditions that could also lead to hyponatermia which shouldn't apply to anyone thinking of a long hike much less a R2R2R.

Could a person develop hyponatermia from excessive use of electrolyte/runners drinks?

No. They could get volume-overloaded (especially with various (mostly serious) medical conditions) and that could create other issues, but since that water went in with sodium, it wouldn't deplete sodium.

Extra credit question from the chemical engineer in the room: If you took potassium salts to excess in the absence of sodium, could you develop hyponatermia?

Extra Credit Answer: Potentially if you were giving only potassium salts but all runners drinks and supplements that have potassium have a balanced amount of sodium. She wasn't sure, but suspected that serious, even fatal results (potassitum chloride is used in pet euthanasia) of high potassium would result before low sodium became an issue. i.e. you'd be dead of a potassium overdose before you developed hypothermia, but that was her guess - not a situation she's managed or could imagine developing unintentionally.

She then discussed how they put a bit of salt and a bit of baking soda in water when they do oral rehydration therapy because the water is absorbed more quickly that way. Sugars also help the water be absorbed more quickly. So I suppose if you WANT to induce hyponatermia, huge volumes of salt-free, sugar-sweetened water without any salt in your solid foods would be most effective. So don't do that.

I'm not doing 30-40 miles on free-range, low-sodium, steamed veggies and a few gallons an hour of pure water. I'll be eating a lot of solid food - a fair bit of it prepared/processed with salt, maybe a bit of gel, some runner's drink mix and lots of pure water to the point of peeing regularly. But HYOH, DYOD, EYOL.

-David

(hike your own hike, drink your own drink, eat your own lunch)
But, as I've posted under the trip thread, I will be bringing micro-brews to share, so you don't have to BYOB. Nor fish - I'll bring the smoked salmon.

Edited by DavidinKenai on 02/13/2012 13:52:57 MST.

David
thanks for your input, it seems to partially disagree with my understanding yet not totally disagree, as water is the culprit. need to digest it a bit.

water retention is a common issue and concern in ultras and seems to be associated with excess salt intake. A common understanding is that this is a forewarning of a hyponatremia issue. Perhaps this is not really the case.

Edited by asandh on 02/13/2012 14:36:41 MST.

Thanks David, that is some great info. Best i could do was ask my friend who is a nurse who agrees with what they said. I could have asked my college adviser (who has a phD in athlete's nutrition) if i had a dog in the fight but i'm not going to call her over an internet debate.

I did not mean to have that get Chaffy but when someone calls ME out questioning my medical credentials (which i have) when that person does not I don't take it very well :)

seriously, have a kick@ss run/hike

Art: Thanks for your civility and grace.

You're right that too much salt can lead to too much water in the body. And that too much water can lead to hyponatermia.

But those aren't sequential - the first is under conditions of excess salt/water and the second is in cases of excess water/salt.

Maybe the bigger message for anyone who could seriously consider a R2R2R (i.e. decently healthy) is that quite large ranges of salt to water are tolerated just fine. Almost all of us get an excess of salt everyday but handle it fine. Most of us underhydrate around town and really need to hydrate better while on the trail. And my sense of the participants is that we've all got the miles under our belt to be reasonably safe.

I really liked Torrey's post about not skimping on water or food to save weight. You can finish a BPing trip without eating on the last day. You can't push yourself on a R2R2R if you short yourself in any way. The exertion, elevation, dryness, sun, and heat are all stressors that add up.

If you want to look this up, you will find it easier as "hyponatremia."

--B.G.--

On longer hikes (longer than ten days), I carry a small whirl-pak of oral rehydration salts (ORS), which I made using a modified version of the WHO low-osmolarity oral rehydration salts recipe (I replaced the glucose with a mix of carbs). If you want to buy commercial ORS (ie, Ceralyte), it will cost you a fortune, but you can make several pounds of it yourself for a couple of dollars. I keep it in my first aid kit to prevent salt imbalance in case I get giardia/crypto on the trail.

Colin, would you mind posting your recipe?

An excerpt from a Runner's World interview with Tim Noakes MD, author of "The Lore of Running"
RWD: How and why do distance runners get hyponatremia?

TN: By drinking too much fluid during very prolonged exercise. We usually find that athletes who develop the condition drink between 1,000 and 1,500 ml per hour [between one and one and a half quarts] during exercise but sweat at much lower rates, perhaps 700-1,000ml per hour. As a result they develop a progressive fluid overload.

RWD: Who gets it most commonly and in what kinds of events?

TN: Women are at much greater risk than men for reasons that we don't yet understand. I think it is purely a size effect; women are smaller and more likely to develop a fluid overload simply because it takes less fluid for small people to become overloaded. Alternatively, it is clear that a big part of the problem is the inability of the athlete to excrete the excess fluid perhaps because of high levels of fluid-retaining hormones. It may be that woman have larger amounts of these hormones, the nature of which remain uncertain.

RWD: How can marathoners make sure they are getting enough fluids but not so much as to be at risk for hyponatremia?

TN: You have to drink a lot for a long time to develop a fluid overload. If runners are drinking less than 1 liter per hour, they are unlikely to develop the condition. Since you need to keep drinking for 5 to 6 hours or more, only very slow marathon runners and ultradistance endurance athletes are at risk.

The best thing for athletes to do is to weigh themselves before and after a hard training workout to determine their usual sweat rate. Then they can plan their fluid intake during a race accordingly.

RWD: How can runners or medical personnel spot hyponatremia in another athlete?

TN: Aside from some medical conditions that are usually well recognized, there are really only two conditions specific to sport that cause an altered level of consciousness during prolonged exercise: heat stroke and hyponatremia. Measuring body temperature is the first step in the differential diagnosis. If the body temperature is above 42 degrees Centigrade, the diagnosis is heatstroke, and the athlete must be placed in an ice-water bath for 5-10 minutes to lower his or her body temperature. If the temperature is normal [i.e., 38-40 degrees Centigrade], then the most likely diagnosis is hyponatremia. The diagnosis can be confirmed by measuring the blood sodium content, and obtaining a result below 129 mmol per liter.

End excerpt.

Dave

Hi All,

There is one other thing to think of that I have come across not mentioned above. Athletes don't always admit it, but some have hypertension and are taking diuretics. These drugs frequently cause hyponatremia, as the patient will be urinating salt water at about 60 mEq/L under the influence of the drug, then they get dry and thirsty. They replace the deficit with water, thus diluting the serum sodium. I have seen the sodium less than 120 mEq/L rarely from this alone.

It is true you can just drink too much water. I saw a man when I was still in medical school who drank 13 liters of water daily. He managed to wash out his kidneys quite nicely and his sodium was very low. Obviously, he worked at it, but even lesser amounts of overindulgences can drop the levels down.

Not everyone is up front about their medications. Overall, diuretic use is close to number one on the causes of hyponatremia list and we see it all the time.

If someone has mental status changes from hyponatremia, I put them in the hospital quickly.

Thanks, steve