Good day, I'm about to have an operation to remove a cyst, I can't tak…

Good day, I'm about to have an operation to remove a cyst, I can't take it anymore, so I need to transfer her to IV, she is only 4 months old, has anyone had such experience? How to make the transition less painful? Only breast milk for her, she doesn't have anything like she falls asleep only with breast or hangs there for hours, but still scary.