When there is rapid or substantial blood loss, whole blood transfusions are routine. In some cases, the plasma component of the blood is removed, leaving only the red blood cells. This packed red cell transfusion is preferred when aiming to restore the oxygen-carrying capacity of the blood. Since blood is a valuable commodity, it is separated into its specific components so that each component can be used where and when it is needed.
Human Blood Groups
It is important to know the blood type of a person because the transfusion of incompatible blood is fatal. The plasma membranes of RBCs bear specific antigens at their outer surface. Identifying the specific antigen present in a person’s RBC determines its blood type.
Since the defense system of the body is so reactive to the introduction of foreign materials, the infusion of an incompatible blood will be interpreted as the intrusion of foreign body. The transfused blood will then be destroyed by the body’s defense mechanism. Thus, blood typing for these antigens should always be done before transfusion.
ABO Blood Groups
Agglutinogens is the specific term referring to RBC antigens since they promote agglutination or clumping. Determining the ABO blood groups are based on the absence or presence of type A and type B agglutinogens. Depending on what a person inherits, his/her ABO blood group will be A, B, AB or blood type O. Blood group O is special since it has no A or B agglutinogen and is the most common ABO blood group. Blood group AB is the least prevalent, having both A and B agglutinogen.
Rh Blood Groups
The Rh blood typing system came into existence after agglutinogen D was found in rhesus monkeys. After conducting studies in humans, the same antigen was found. Among the 45 indentified Rh agglutinogens, only three are fairly common. The three common Rh groups are agglutinogen C, agglutinogen D and agglutinogen E.
Unlike the ABO system antibodies, anti-Rh antibodies are not present in the body. However, if an Rh negative person receives an Rh positive transfusion, then the body will make anti-Rh antibodies. It is important to note that hemolysis does not happen with the first transfusion since there are no anti-Rh antibodies present yet but after the first transfusion, hemolysis can occur.
Transfusion Reactions: Agglutination and Hemolysis
Transfusion reaction happens when a mismatched blood is infused. What happens is that the red blood cells of the donor are attacked and destroyed by the recipient’s plasma agglutinins. The first reaction of the body is to clump together the foreign RBCs. This is called agglutination and it causes blockage on the small blood vessels throughout the body. After being clumped together, the RBCs are destroyed by phagocytes and they rupture, releasing hemoglobins into the bloodstream. The free-circulating hemoglobin poses a very serious threat because it may reach the kidney tubules, causing cell death and then potentially leading to renal shutdown. If this happens, the person may die.