Back in the 90s while developing software for blood banking, I was surprised to discover that it was not uncommon to administer blood transfusions to dead patients. If a patient is brain dead (IOW would not survive unaided for more than a few minutes), they would keep them on life support until their organs could be harvested. It was usually only a day or two and the goal was to ensure that the organs would be viable.
I worked in a 72 bed OR that was a major transplant center. Virtually all the nurses I worked with, including myself, refused to be organ donors. Viable organs can’t be harvested from a dead body.