I just read a little bit on it, I wonder if this particular runner had issues with his kidneys...

"Intoxication with salt-substitute, potassium-containing dietary supplements, or potassium chloride (KCl) infusion. Note that for a person with normal kidney function and nothing interfering with normal elimination (see above), hyperkalemia by potassium intoxication would be seen only with large infusions of KCl or massive doses of oral KCl supplements."

I have not heard of this happening before otherwise.

That is some scary stuff.

Wow! This endurance stuff is risky business.
If you don't exercise it will kill you and if you exercise it will kill you. ;-O

OH, btw, if you press "post comment" twice while your computer is hanging, then it will post twice. And, you can't delete the post. Anyways, that explains this second post.

I cannot believe I am reading this. About 5 years ago, I was trained and ready to complete my first marathon when a common cold came over me. I went to the school health center who thought this might require blood work (?) as they believe any symptom does. Anyway, the results came back that I was extremely hyperkalemic, bordering on fatal levels of potassium in my body. Of course, I thought this to be a bunch of crap but they insisted I see every doctor under the sun and forbid me to run. Once I stopped running, my potassium levels normalized and there was never another connection made but that it stemmed from my training. I have now began running, swimming and biking again and have not had my levels checked but think maybe I should consult some medical supervision? I am eager to see any follow up on this situation that anyone finds.

I did some reading about this mostly on emedicine. There are 2 (at least) articles on hyperkalemia. There are many causes.
Trifly, if you had such extreme results with a health center that you don't seem to have much confidence in, it may have been an artifact of the blood draw technique. Of course, if you may have taken something for your cold symptoms that included something like aspirin or ibuprofen, that could have contributed to an actually high potassium level. And since it's easy to become dehydrated when you have a cold, it would probably easy to concentrate your salts including K+. If a runner had any mild cold symptoms before a race and was slightly dehydrated, and took something for the cold and then used salt and/or potassium tablets in an attempt to try to feel normal again (mistaking dehydration symptoms for symptoms of low electrolytes), it would be easy to throw things way off balance (the body is amazing about keeping salts and hydration levels just right, in spite of all the things we try to do to thwart it). As a grad student in pharmacy, Nickel could probably have explained this to us best.
Potassium is measured in the plasma (blood), but it moves in and out of the plasma and other tissues/cells.The wiki article cites a Sports Med article about potassium regulation in plasma and skeletal muscle during exercise. The abstract says that during exercise, potassium is released from working/contracting skeletal muscles into the plasma. The amount released depends on things like level of training, medications, and caffeine (this release of potassium may also affect our feelings of fatigue). Potassium is in turn also taken up by non-contracting tissue, which "may be important in preventing plasma potassium from rising to excessive levels." When exercise stops, especially if it was intense, there is a steep drop in plasma potassium (as it goes back into muscles). "The rapid increases and decreases in plasma potassium with onset and cessation of exercise, respectively, has been implicated in altered myocardial function and sudden cardiac death." Another potential cause of this for Nickel may have been rhabdomyolysis (=breakdown of muscle fibers which causes leakage of potentially toxic cellular contents [such as potassium] into circulation), which "may occur after excessive muscular activity, such as ... sporadic strenuous exercise (eg, marathons)." It can also be caused by viruses like flu and bacterial infections like strep. Whatever happened to Nickel, my minimal understanding of these things suggests that it was probably some unfortunate exquisite coincidence of very particular random things.