It is a great story. I picked up a German reprint (in English) of the 1974 London printing not long ago.
As for the blood credits, according to the story, Buk got the transfusions after mentioning his father to either a nurse or doctor. His father had apparently donated blood in the past, so he had credits that Buk could use. It's interesting that Buk doesn't seem to have a bit of gratitude toward his father for that. To me, that has always effectively sealed Buk's resentment toward his father based on childhood experiences, largely written about in Ham on Rye. Whether or not that resentment was completely justified is, of course, another matter.