cryonics seems to require signing up for a DNR
What did you read that makes it seem this way? I haven't run into this before.
A variety of places mention it. Alcor mentions it here. Cryonics.org discusses the need for some form of DNR although the details don't seem to be very clear there. Another one that discusses it is this article which makes the point that repeated attempts at resuscitation can lead to additional brain damage although at least from the material I've read I get the impression that as long as it doesn't delay cryopreservation by more than an hour or two that shouldn't be an issue.
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