What could cause sudden changed in my mom's mental state?

My mom is 81 and had been doing pretty well with what I considered very minor alzheimer or dementia. We just saw her Dr. about a month ago and at that time she was doing fine. By fine, I mean that she had her memory issues but nothing that affected her daily living as long as I handle her money and medicines etc. She lives on her own in a small senior apartment and had actually been doing even better than normal.

Well, recently mom had some episodes of blood in her stool and I eventually ended up taking her to the hospital. They ended up doing a colonoscopy and putting a camera down her throat to check for ulcers, In the end they found an ulcer in the upper GI that we are now treating with meds. The problem is that since this happened she seems to have a lot less snap then she had before. I am thinking that the drugs used to put her to sleep for these tests have done something to her mentally. This makes sense to me because her Dr. had previously not wanted her to take Ambien or sleeping pills because he says they are not good for people with memory problems.

Has anyone else had this problem and if so do you think her memory will improve again or should I consider this permanent? Also, if this is reality wouldn't you think Dr's would be very cautious about putting someone under that already has ALZ?