I'm from midwest(1200' elevation)in 2008 did ( attempted) full peak marathon. Just after A-frame 11,000 or so elevation I started to get sleepy, head aches, tired, just wanted to lie down and sleep...And basically is want I did until I was found and given oxygen and then conituned on the rest of the race as a nonm-finisher. BUT up in the high thin air I was just as you mentioned. A couple cards short of a full deck so to say. As soon as I got back down to around 7500" I was good to go once again. I did hydrate the whole way... but guess i'm not a elevation man...
