“Can I prevent constipation after anesthesia?”

Yes
Keep hydrating and you can add a laxative to help for the first few days after the operation

If its not a bowel surgery you should not have a problems with constipation. Anesthesia is not causing that problem. But surgery and dehydration could. Especially ileus after bowel procedures. Surgeons usually have a protocols that they follow postop to stimulate the bowel. That includes hydration, early ambulating postop, as well as diet with plenty of fiber and laxatives.

Stay hydrated with electrolyte water. Drink at least 1,000 ml of probiotics every day. Take magnesium, vitamin d and evening primrose oil daily.