As part of the precautionary prep:
Keep a small notebook and pen with you while in the hospital, and note down as best as you can everyone you interact with at the hospital. If you're feeling too drugged to write, ask the person -- or whatever nurse or assistant might be with them -- to write their name and position down for you. You want to be able to keep track of who actually operated on or touched you or reviewed something for you so later you can check the bill to make sure no one extra appears. In my own case, hospital tried to charge me an extra $10,000ish for an anesthesiologist that never showed up and another few thousand for a doctor who never came to see me. It helped my case that I had notes (including in some hospital staff's writing) to show both were bunk.
Do the same (as best you can) with what meds you take during your stay. Along the $15 toothpaste lines, I was charged $45 for ONE aspirin that I never was prescribed, received, or took.
If you're heavily drugged, the above isn't easy, but do the best you can. If you have someone who can stay with you for periods and do the note-taking, that's also helpful.