Yes I understand that, but what you do not seem to realize is that plasma volume expanders (Ringer’s lactate solution, dextran, hydroxyethyl starch, and others) are used to maintain blood volume thus preventing prevent hypovolemic shock and allowing the transportation of existing red cells to vital parts of the body, whilst it is making new red cells in the bone marrow. These expanders were used on my friends and they recovered very quickly with no post operative complications. Remember that they were told that they would die too.....but they didn't.
Genetically engineered proteins can stimulate the production of red blood cells e.g. EPO (erythropoietin)
Other medications greatly reduce blood loss during surgery (aprotinin, antifibrinolytics) or help to reduce acute bleeding (desmopressin).
Some fluids now being tested can transport oxygen. Scientists have been working to develop artificial blood for years, taking away the dangers and risks associated with whole blood transfusion.