[pct-l] Hyponatremia

[waynekraft at verizon.net (Wayne Kraft)]

I am not a doctor, so maybe you shouldn't listen to me.  However, in the 
last four years I've run six marathons, at least a dozen half marathons, one 
50k ultra, one 200 mile relay race, dozens of 20 mile training runs, 
participated as an assistant coach in a marathon training group and read 
everything I could find on proper hydration.  Based on all that, I am 
surprised to see hyponatremia mentioned here.

Among all the problems that occur in this area, dehydration and insufficient 
carbo replacement are far, far more common than hyponatremia. In my 
experience hypnatremia occurs when someone engages in a serious endurance 
activity and rehydrates only with water, avoiding sports drinks and food.  A 
hiker with normal metabolism who walks, snacks on carbs and something with a 
little salt in it should never experience hyponatremia.  Unless you are 
pressing very hard for a long time in hot weather and ingesting nothing but 
water, I would be leary of blaming physical problems on hyponatremia; 
however, the usual treatment for it (drink some sports drink and have a 
salty snack) are not going to hurt you even if you aren't experienceing 
hyponatremia.

I am aware of one situation in which a physician sued the directors of an 
marathon race because he had hyponatremia induced siezures while on a plane 
returning from the marathon which resulted in brain damage and ended his 
career.  The doc claimed that the race directors were at fault for providing 
TOO LITTLE water and I'm guessing that the doc thought he was dehydrated 
after the race and rehydrated copiously with water alone.  I don't know how 
the lawsuit came out, but every marathon in which I've participated provided 
sports drink and snacks to participants.  IMHO, the doc should have been 
able to avoid hyponatremia just by availing himself of these offerings. 
Personally, I carry a water bottle on a waist band with a few carbo gel 
packs and some electorlyte replacment caps whenever I go long so I'm never 
dependent on someone else.

I did perform one bizarre, ill-advised personal experiment in this area.  I 
ran a half-marathon after two weeks on a zero carb diet and ingested nothing 
but water for the first 10 miles on a pleasant, cool spring day.  I was fine 
for the first 9 miles (90 min. +/-) and between mile 9 and 10 the lights 
went out. This was quite sudden and obvious.  I began to experience tunnel 
vision and poor balance and was reduced to a  walk. I gobbled a gel pack and 
was back to a jog in about 10 minutes and was able to finish the race.  A 
cheeseburger, fries, microbrew and nap returned me to normal within a few 
hours.  This was clearly an example of extreme carb depletion, not 
hyponatremia.

If you rehydrate reasonably and take in food regularly, I would be very 
surprised if anyone would experience hyponatremia while backpacking. I've 
tried to imagine a situation where hyponatremia might sneak up on you over a 
period of several days of reduced food intake, but given the sodium content 
of the stuff we normally pack with us, this really seems unlikely.

Wayne Kraft