Electrolytes and "hitting the wall"

when I did my 16 miles on Monday, I felt like I was goinmg to pass out several times.
This was because when a person runs that far, he or she must replace sugars and elctrolytes, often done through a swig of Gatorade. I hadn't had any and by the time I got in the shower after the run, I nearly blacked out.

Runners running beyond 18 miles must replace sugars. And death can occur when an unprepared individual hits the "wall". The human body was not meant to run this far and artificail replacement of this nutrients is absolutely essential. This is often done with gels and forms of bars. At the Chicago marthon, these are passed out at mile 18.

I've leaned my lesson this time...