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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