DD has had one, and I'm not sure it is this way at every hospital, but we were at Seattle Children's for ours.
DD had the hardest time with the fasting. We were scheduled for 11:45 and ended up waiting 3 hrs before the actual procedure...horrible to wait over lunchtime, so try to schedule 1st appt early in the morning, it was this way for our other procedures at a normal hospital where the baby got priority over the adults (not possible at a children's hospital).
So, anyway, DD was fine after the wait was over. She had general anesthesia and I was able to hold her as she went to sleep with the gas, then they started the iv after I put her down on the bed. They move very fast at that point and we were taken to her recovery room to wait at that point. She came back asleep still and we were with her as she came to. She was STARVING but we had brought her fav snacks so she ate and drank water right after waking back up. Overall, it was fairly easy but the wait was difficult, to say the least.
GL!! T&P headed your way.
My daughter had one when she was 2.5 years old. Try to get an early appointment so the fasting won't be such a big deal.
It took about 40 minutes or so and it was not bad at all. I was a nervous wreck before the procedure so I definitely understand your concern. Try not to worry.
J's had a few brain MRIs done. In fact, he has to have an MRI done tomorrow for cysts on his spine. They always tell us, no milk or solid foods after midnight and he can have all the jello and clear fluids (pedialyte, apple juice, water) that he wants until three hours before the scan time.
I suggest telling them to use the gas to put her under before they put the IV in. Otherwise she will probably fight the IV and she'll get a bruise around the IV site. J HATES being held still and would fight them so bad they couldn't get a good stick. His first two or three MRIs, he came home with bruises on both ankles and both wrists from that.
The scan usually takes an hour for us, but ask the technician just to be sure. I also suggest making sure they call you as SOON as she's out of the scan room, so you can be there when she wakes up. They won't let you in the scan with her. The second-to-last time J had an MRI, he woke up under a bright light with three nurses, but no one he recognized and they called me into the room with him absolutely freaking out and they couldn't calm him. It took me almost a full hour to get him to settle down. He was almost two at the time. At his last MRI (age three), they called me the minute they pulled him out of the scan and into recovery, so I was there when he woke up and we didn't have that issue.
She'll probably be groggy from the anesthesia. They'll tell you to watch for extra sleepiness and to call the emergency room if she won't stay awake, but we've never had a problem once he's up. J doesn't like to eat for a few hours afterward, and when he does eat he wants something easy to eat, like Jello and juice.
She'll be fine, and so will you. Be sure to bring something with you to occupy yourself while you wait - a book, magazine, something.