Hi,
This has happened to Heather. When she had her PEG tube inserted, it was to be a "twilight" anesthetic, so she would be awake, but not aware. Well, she was definitely aware. She said it was like she was wide awake. She saw and heard everything they did.
When she was 7 and had her tonsils out, the stuff they gave her to relax her instead did the opposite and she was bouncing off the walls. And after her surgery last September, when they gave her Adavan (sp?), instead of helping her to sleep, she had nightmares and was hallucinating. According to the doctor, she had what is called a paradoxical reaction. I'm sure it's more complicated, but I think basically it means you get a reaction opposite to what is expected.
I don't have an explanation as to why this happened to you now and not before, but I wonder if they used a different med this time. I would definitely let the doctor know and make note of what med it was, so you know for the next time.
Rainbows & hugs,
Rosie