IMPORTANCE OF ABO GROUPS IN BLOOD TRANSFUSION

IMPORTANCE OF ABO GROUPS IN BLOOD TRANSFUSION

During blood transfusion, only compatible blood must be used. The one who gives blood is called the ‘donor’ and the one who receives the blood is called ‘recipient’. While transfusing the blood, antigen of the donor and the antibody of the recipient are considered. The antibody of the donor and antigen of the recipient are ignored mostly. Thus, RBC of ‘O’ group has no antigen and so agglutination does not occur with any other group of blood. So, ‘O’ group blood can be given to any blood group persons and the people with this blood group are called ‘universal donors’. Plasma of AB group blood has no antibody. This does not cause agglutination of RBC from any other group of blood. People with AB group can receive blood from any blood group persons. So, people with this blood group are called ‘universal recipients’.

MATCHING AND CROSS-MATCHING

Blood matching (typing) is a laboratory test done to determine the blood group of a person. When the

person needs blood transfusion, another test called cross-matching is done after the blood is typed. It is

done to find out whether the person’s body will accept the donor’s blood or not. For blood matching, RBC of the individual (recipient) and test sera are used. Cross-matching is done by mixing the serum of the recipient and the RBCs of donor. Cross-matching is always done before blood transfusion. If agglutination of RBCs from a donor occurs during cross-matching, the blood from that person is not used

for transfusion. Matching = Recipient’s RBC + Test sera. Cross-matching = Recipient’s serum + Donor’s RBC.

INHERITANCE OF ABO AGGLUTINOGENS AND AGGLUTININS

Blood group of a person depends upon the two genes inherited from each parent. Gene A and gene B are dominant by themselves and gene O is recessive. Agglutinogens appear during the 6th month of

fetal life. Concentration at birth is 1/5 of the adult concentration. It rises to the adult level at puberty.

Agglutinogens are present not only in RBCs but also present in many organs like salivary glands, pancreas, kidney, liver, lungs, etc. The A and B agglutinogens are inherited from the parents as Mendelian phenotypes. Agglutinin α or β is not produced during fetal life. It starts appearing only 2 or 3 months after birth. Agglutinin is produced in response to A or B agglutinogens which enter the body through respiratory system or digestive system along with bacteria. Agglutinins are the gamma-globulins which are mainly IgG and IgM immunoglobulins.

TRANSFUSION REACTIONS DUE TO ABO INCOMPATIBILITY

Transfusion reactions are the adverse reactions in the body, which occur due to transfusion error that involves transfusion of incompatible (mismatched) blood. The reactions may be mild causing only fever and hives (skin disorder characterized by itching) or may be severe leading to renal failure, shock and death. In mismatched transfusion, the transfusion reactions occur between donor’s RBC and recipient’s plasma. So, if the donor’s plasma contains agglutinins against recipient’s RBC, agglutination does not occur because these antibodies are diluted in the recipient’s blood. But, if recipient’s plasma contains agglutinins against donor’s RBCs, the immune system launches a response against the new blood cells. Donor RBCs are agglutinated resulting in transfusion reactions.

Severity of Transfusion Reactions

Severity of transfusion reactions varies from mild (fever and chills) to severe (acute kidney failure, shock and death). Severity depends upon the amount of blood transfused, type of reaction and general health of the patient.

Cause for Transfusion Reactions

Transfusion of incompatible blood produces hemolytic reactions. The recipient’s antibodies (IgG or IgM)

adhere to the donor RBCs, which are agglutinated and destroyed. Large amount of free hemoglobin is liberated into plasma. This leads to transfusion reactions.

Signs and Symptoms of Transfusion Reactions

Non-hemolytic transfusion reaction

Non-hemolytic transfusion reaction develops within a few minutes to hours after the commencement of blood transfusion. Common symptoms are fever, difficulty in breathing and itching.

Hemolytic transfusion reaction

Hemolytic transfusion reaction may be acute or delayed. The acute hemolytic reaction occurs within few minutes of transfusion. It develops because of rapid hemolysis of donor’s RBCs. Symptoms include fever, chills, increased heart rate, low blood pressure, shortness of breath, bronchospasm, nausea, vomiting, red urine, chest pain, back pain and rigor. Some patients may develop pulmonary edema and congestive cardiac failure. Delayed hemolytic reaction occurs from 1 to 5 days after transfusion. The hemolysis of RBCs results in release of large amount of hemoglobin into the plasma.

This leads to the following complications.

1. Jaundice

Normally, hemoglobin released from destroyed RBC is degraded and bilirubin is formed from it. When the serum bilirubin level increases above 2 mg/dL, jaundice occurs.

2. Cardiac Shock

Simultaneously, hemoglobin released into the plasma increases the viscosity of blood. This increases the

workload on the heart leading to heart failure. Moreover, toxic substances released from hemolyzed cells reduce the arterial blood pressure and develop circulatory shock.

3. Renal Shutdown

Dysfunction of kidneys is called renal shutdown. The toxic substances from hemolyzed cells cause

constriction of blood vessels in kidney. In addition, the toxic substances along with free hemoglobin are

filtered through glomerular membrane and enter renal tubules. Because of poor rate of reabsorption from renal tubules, all these substances precipitate and obstruct the renal tubule. This suddenly stops the formation of urine (anuria). If not treated with artificial kidney, the person dies within 10 to 12 days because of jaundice, circulatory shock and more specifically due to renal shutdown and anuria.

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