JW's do this in prisons as well and they've been doing it in hospitals for a long time. I'd rather be told I could live on a paradise earth than burn in hell. Although, depending on which day it is or who you're sharing a hospital room with that might not be the case.
Funny thing is: I've heard many a story of non-Witnesses who don't want blood transfusions say they are witnesses to their doctors so they will use other methods. And if a witness goes and talks to that person, because the docs say they are a witness too, lo-and-behold they are not. Very strange.