Here, I'll speak from emotion, and not legal. I do not believe so. There is always the DNR advance directives of elderly, and not so elderly, people, currently in good relative health, who do not want what I have heard described as "heroic efforts" to save them, if they expire. If I understand them correctly, when it's "their time", that is it. Let them go, they are going to "a better place".
Tangent, here: Momma B has expressed her desire, when it is "her time", that any body part that can be used in a transplant, be so utilized, as at that point, she won't be actively needing them. In a weekly newspaper column we write, she has mentioned that doing so is her bit attempt at immortality, even if it is only a corneal transplant that will live on.
When my father died, his eyes went and helped at least 2 other people, and his skin was used as temporary dressing on a burn patient.
Momma B and I are signed up as organ donors, and suggest if you want that bid at immortality, also, that you, also do so.