Perhaps that was one case, however, you must admit that blood transfusions are necessary in many cases — especially if you have lost or could lose blood?
Concerns about the safety of the blood supply caused a movement among surgeons to either eliminate of minimize blood use, not out of religious objections but concern for an infection by an agent they couldn't test for except by it's association with Hepatitis C.
Although even heart surgeries had been performed without transfusions since the early 60’s concern over the safety of the blood supply propelled the movement toward bloodless surgery for strictly medical reasons apart from patients religious views. Today bloodless, no blood transfusion, surgery is common, far more so than even 20 odd years ago.
As to the necessity of blood use or not, I'm not a physician but obviously the number of cases where transfusion is considered necessary has diminished by miles just as the percentage of premature babies treated and surviving has grown due to medical advances.
As with abortion due to medical necessity transfusion of blood for medical necessity is a term proving obsolete.