[whatshisface]

>Is there an outside definition of medical ethics that can really be impartially compared from generation to generation?

That's a legitimate criticism of doing anything, but the problem is that it applies to, well, anything. Anything you do today could be seen as a horrifying atrocity by future generations, unless there exists some kind of boundary on what ethical stances a culture might adopt. There could be limits, but in that case there is an outside definition of medical ethics. If there isn't an outside definition then maybe in 100 years haircuts will be seen as mutilation[0].

[0] There are some cultures with strict rules about facial hair, so even though this example might sound ridiculous it actually serves to illustrate the point.