What are some outdated medical dogmas that are still taught or practiced?

Hi, I’m a nursing student and I’ve noticed that certain practices in healthcare seem to stick around even when the evidence shows they’re not effective. For example, Trendelenburg positioning for hypotension is still commonly taught in nursing despite being shown to have no real benefit. Or risk of hyperK arrest in someone who’s only been crushed for 30 minutes. I’m curious to hear what other dogmas people have come across that are still being taught or practiced despite newer evidence proving otherwise. Also, how do you confront people about these in a respectful manner, especially as a student?