This may or may not be related but look into "water poisoning"
From
http://chemistry.about.com/cs/5/f/blwaterintox.htm
"Water intoxication and hyponatremia result when a dehydrated person drinks too much water
without the accompanying electrolytes."
I rode with a gal who had this happen to her, it is very scary and deadly in it's most sever
form. You get drilled into your head to drink drink drink, but they never talked about the
need for electrolytes.