Today, we were talking about hypoglycemia, and if you talk to people who finished their training only a few years ago and you'll hear the words, "Hyperglycemia doesn't kill anyone. Better to be high than low." This has been dogma until recently, when several nice studies have shown that poorly controlled glucose in critical patients increase mortality up to 15%. Now, the thinking is the opposite. I've actually told patients that hypoglycemia is the price you pay for good glucose control.
Then, there's pulmonary artery catheters. 4 years ago, this was a bread and butter procedure for internal medicine residents. Now, I don't know any resident that's done more than one. Looking a little further back, there's beta blockers in heart failure, the use of thrombolytics, stenting versus CABG, anti-TTG Ab versus duodenal biopsy.
My point is that medicine is a field of constant change, and not little change. Big change. Talk to a doctor 15 years ago, and if you told him that you thought that his heart failure patient didn't need a Swann and should be on a beta blocker, he'd accuse you of malpractice (and 15 years ago, he'd have been right!).
Some people like fields that are understandable and consistent. Medicine is not such a field. If the thought of continually keeping up with the changing world of medicine scares you, then you'd best stay away.