You could go to www.google.com (my favorite search engine) and type in "tying up syndrome in horses" you'll find a ton of info.
I had a mare that used to ty up all the time. I'm sure yours is more of an isolated incidence. Maybe needed electrolytes? Maybe over worked for his condition?
You should also go to Susan G's web site, she has some good info:
http://www.shady-acres.com/susan/beetpulp.shtml
Personally, I would take her off the oats, and put her on grass hay only. No reason for all those oats. A high fat, low carb, diet is supposed to help.