We've had two, the first was without sedation because she was pretty young. I hated it, she cried herself to sleep in there eventually and it was just awful. The second time she was a little older and they did sedation, it wasn't full sedation but close- they let me hold her as it was administered and she went noodle limp and totally asleep which is alarming to feel. She needed surgery and that was full sedation, they gave her some medicine to help keep her calm and wheeled her away while she was awake and happy before administration. Both the partial and full anesthesia she was pretty 'normal' after, but kinda groggy for a few hours. I would plan to just let them nap after if they want and call the day a wash as far as keeping to a tight nap schedule. Is it at a children's hospital? I know it's so scary but just keep asking questions, even your unhinged ones, your team likely has heard it all and understands and will do their best to give you some comfort.
I would defined try to schedule around morning depending on your little one’s age as there will be a cut off time before sedation from food and liquids. My son had an MRI in the NICU so i can’t really help there but he just had a renogram at almost 10 months (a different machine he had to be still for) and they did moderate sedation. We BF and so he had to stop feeding 4 hours before check in and all clear liquids 2 hours before check in it is longer for formula. It may also differ for levels of sedation and by hospital. We were able to be with him while they administered the IV and the catheter and walk him to the scan but had to stay in a separate waiting room while they did the actual scan. He was awake pretty soon afterwards but sleepy most of the day but he didn’t sleep too much more than normal that also will depend on each child.
Both of my twins had an MRI at about 2 months corrected age, they didn't use any sedation, they were just settled to sleep and had a little nap while the MRIs were done. I didn't find the actual MRI stressful, it was just the worry of what they would show that got to me.
My son was 7 when he had one so no advice for a baby sorry - but I know the anxiety.l and it’s not nice. They will be lovely and reassuring on the day to help settle your nerves. I hope all goes ok for you and your little one x