I had to go 48 hours w/o nursing my then-2 mo last month. Fortunately I knew it would happen since before he was born since it was a scheduled thing (MRI with contrast - the contrast i s the problem). Unfortunately, I had understood it would 24 hours and had stored up exactly 50 ozs by then, then the day of found out it would be 48 hours and DS probably should have had more milk than I had saved. It was hard for me bc DS kept wanting to nurse and it made me cry that I couldn't let him. He'd take the bottle, and fast, but then still turn to the breast and it was so sad. Then after two days of bottles, it took some extra time and effort to get him back to nursing well. Hopefully your experience will be better and a much shorter timeframe.
The anesthesia is waht matters. What are you having for that? If you get general anesthesia, they usually say wait 24 hours to nurse again. If you get local, no wait time necessary.
If you';re gonna need to bottle feed, start pumping and storing today. A lot of ppl recommend pumping once after baby goes to bed if you're still awake, right before you go to bed. Then after baby's first morning feeding since you'll probably have more milk then. You can also pump after every feeding, you mihgt only get .5 oz but it will add up quickly over the day and stimulate more production.
If you're in dire need to get more saved fast, and baby is sleeping four or more hours, get yourself up to pump every 2 hours while baby sleeps.
For feeding, try a bottle on baby today. Most babies will take it esp if it has a level one nipple. If not, try cup feeding with a little medicine measuring cup, slowly so baby doesn't choke on it. Cup feedings are done for LO's right after birth who need bottles to avoid nipple confusion, so your LO should do fine at this age.
Good luck with the procedure and the restarting of nursing! Hope you don't end up in too much pain!
ETA: to keep your supply up, pump every time baby eats during the bottle-feeding hours. So if baby eats every 2 hours, pump every 2 hours. Easiest to do right after baby eats so you're on the same schedule.