It's not that unrealistic for a transplant specialist to have psychological issues. I don't think I could do it. You literally have to decide (albeit by a very numbers-based approach, but still...) who lives and who dies whenever an organ becomes available. Someone has died, and there are organs coming from that person; Those organs will determine the outcome of many other peoples' lives. You are charged with determining whose life changes and whose life ends. Could you bring yourself to terms with the idea that someone else dies because you elected to give the organ they needed to someone else?
I sometimes wonder if my kidney donor would think I am worth his life, or if the people who died waiting for the kidney I was given would think I am worth their deaths.