Our son had a spinal & brain MRI w/ sedation when he was 3. We were quite nervous about it and looking back, we didn't have much to worry about. We had ours done at CDH. We talked a lot with our son to prep him for what was coming (in particular the IV). We focused a lot on the night before - how it was going to be so exciting to stay up late and watch new movies (he needed to be short on sleep so we had a long movie night). His MRI was first thing in the morning so we didn't have to explain "fasting" to him - he ate an early dinner and skipped breakfast.
We showed up and were escorted into a room and they started prepping right away. He wore sweatpants & a sweatshirt and was allowed to stay in them. They asked me all kinds of questions about allergies, etc. The IV went in quick and he cried a little but nothing too traumatic. They inject the sedative into the IV, I talked with him the whole time and before you knew it he was sound asleep. There was a bit of a back-up that day in the MRI so there was some concern that he would wake up during the MRI. They gave him a little extra in the room but during the MRI, sure enough, he did start to stir as they moved him. They gave him another dose about 3/4 of the way through the MRI so they could finish. Every time he would start to stir they would stop and wait 5 minutes - as you can imagine that really added up and he was under sedation a lot longer that expected. That last does of sedative also meant it was going to take longer for him to wake up. If I remember correctly, he was in the MRI about 3 - 3.5 hours and then it was about 2 hours till we left. When he woke up it was like dealing with a really drunk person (get ready for some really funny stuff to come out of their mouth). He was able to walk out of the hospital but he wasn't steady and I kept an arm under him at all times. We had a bucket in the car - just in case - but he was fine. (he threw up once we got home.) At home, my husband had propped him up on the couch watching TV and left the room to get some water - the next thing we hear is a big "thump". He had slumped right off the couch! Pretty funny, again, kind of like dealing with a drunk. My advice would be to sit on the floor for a while! I think we eased back into food - I had made some jello for him to eat at first (almost like having the flu).
Let's see, a detail I was surprised about: while he was in the MRI I couldn't stay in the room or go with them so I was in a waiting room. That was killing me because I felt really out of the loop. There was a nurse at a desk in the room and I probably asked her for an update every 20 minutes. I did start to get concerned when things ran over the 2.5 hours I was told it would take and no one came out to explain why - hopefully Children's will be better about that!
I just asked my son (who is now 6 1/2) what he remembers: the IV needle going in, he had his blanket, he got Indiana Jones Legos afterwords and he threw up.
I'd be happy to answer any other questions you have - just shoot me a note!