If you think about it, the purpose of a transfusion is to add hemoglobin to the bloodstream for the body to be able to take in oxygen. This is a means to allow the same thing but it takes longer, usually the JW is given a drug that encourages the body to create more red blood cells at the same time.
Because it takes longer than a transfusion, it is not ususally suggested to the average patient, when time is of the essence, in many cases.
I am not a doctor/nurse, but a quick glance at the procedure seems to indicate that.
I have talked to surgeons about this and it is an effort used mostly with patients that won't take transfusions. They were not too impressed by it since other procedures are more useful and timely.
Blondie