This therapeutic process is one of the most important life saving techniques. Its indication is primarily to replace the blood lost due to injury, burns, surgical operations, etc. Blood transfusion is also indicated in certain anemia, e.g. aplastic anemia.

   Universal donor and recipients

In the past, group O person used to be called a universal donor because group O RBCs do not contain any of the antigens responsible for ABO blood group system. Such type of RBCs when transfused into a person belonging to any of the ABO system are not agglutinated because the recipient’s plasma agglutinins do not encounter any antigen to react with. On the other, the anti-A and anti-B agglutinins which are present in the transfused group O blood become highly diluted by the recipient’s plasma because the amount of the recipient’s plasma is usually much larger than that of transfused. It is thus obvious that with a small blood transfusion the significant factor is the action of the recipient’s anti-bodies on the transfused RBCs. However, if the antibody titer of the transfused blood is very high or if blood group O is transfused in large amounts, then the quantities of anti-bodies in the transfused blood becomes significantly increased and may lead to the destruction of almost all the RBCs of the recipient’s own blood.

Group AB was called universal recipient as this blood does not contain any agglutinins against any ABO blood groups. But if a person with blood group AB is transfused with a large amount of group O blood which contains both anti-A and anti-B agglutinins, there may occur a marked agglutination of the recipient’s RBCs. The same can also happen if a group AB subject is transfused with blood containing an excess of anti-A or anti-B agglutinin as by transfusing a large amount of blood belonging to group B and A respectively.

It is apparent from the above discussion that the terms universal donor and recipient are incorrect and misleading and should not be used. Another reason why these terms are now obsolete is that these terms do not take Rh factor into consideration.

   Test done before Transfusion of Blood

1. Typing of Blood Groups
This means the determination of the ABO and Rh blood groups of both the recipient and the donor. Blood for transfusion is selected which has the same ABO and Rh groups. However, as mentioned above, with a few exceptions small amounts of blood group O can be given to subjects with any of the ABO group; also with group AB can be given small amounts of blood of any ABO group.

2. Cross Matching
After typing of blood groups, the donor’s blood is subjected to direct or cross matching with the recipient’s blood. In this test, the patient’s serum is incubated with the RBCs of the donor to detect the presence of any antibody in the patient’s plasma that might produce antigen-antibody reaction with donor’s RBCs.

   Incompatible Blood Transfusion

It must be well understood that the necessity of blood transfusion should be given due consideration because it is potentially hazardous and even fatal if incompatible blood is transfused. For these reasons, the doctor asking for a blood transfusion should be fully convinced that blood transfusion is absolutely essential.

The first sign of an incompatible blood transfusion is the production of chills, pain in the back, tightness in the chest, anxiety and restlessness. A doctor or a nurse should be present in the initial stages of blood transfusion to look for these reactions. If any doubt arises about the compatibility of the transfused blood, the transfusion must be stopped at once. If the mistake is not detected and corrected in time and more of incompatible blood gets entry into the patient’s circulation, the reaction becomes more severe. The agglutinated RBCs undergo hemolysis which leads to hemoglobinemia and hemoglobinuria. In severe cases, shock and renal insufficiency make their appearance and the patient may even die.

   Blood By-Products and Substitutes

1. Packed cells: These are transfused in those cases which need only RBCs and in which it is not desired to increase plasma volume.
2. Plasma: The plasma of blood not used for transfusion can be removed and freeze-dried or lyophilized. It can then be stored for many years. When a plasma transfusion is needed, it is reconstituted by adding sterile pyrogen-free distilled water. Plasma transfusion is needed when physician wants to increase only the volume and not the oxygen carrying capacity of the blood.
3. Free frozen Plasma: It is separated from blood within 24 hours of its collection. It is rich in many factors needed for blood clotting. It is especially useful in controlling bleeding in patient of hemophilia.
4. Antihemophilic globulin-rich cryoprecipitate: Like fresh frozen plasma preparation it is used to control bleeding in hemophiliacs.
5. Protein fractions from Plasma: Plasma can also be used to prepare various protein fractions which are of much use in therapeutics. These are given below:
   Fibrinogen: It is used for making fibrin foam.
   Prothrombin and thrombin: These are used in skin and nerve grafting.
   Gamma globulins: These contain immune bodies and are used as prophylactic agents for many infectious disease, e.g. measles.
   Albumin: It is used as plasma expander and in disease in which the circulating albumin is low.
   Dextran: It is not a blood by-product but a substitute for plasma.