4. Clotting Mechanism:
Clotting factors are necessary for the formation of prothrombin
activator. Prothrombin activator is formed by two pathways:
1. Extrinsic pathway.
2. Intrinsic pathway.
5.
6.
7. The third step in clotting
mechanism is conversion of
fibrinogen to fibrin.
• The thrombin acts on
fibrinogen and converts it
to fibrin fibre.
• These fibres ultimately
form a meshwork in which
platelets, blood cells and
plasma get entangled. This
is known as clot.
10. BLOOD GROUPS
Blood is categorized into different groups
based on their antigenic properties.
Karl Landsteiner discovered blood
groups. Most important blood group
systems are the ABO and Rh systems.
11. ABO system:
• Human blood is categorized into 4 major groups depending on
the presence or absence of antigens. Antigens are present on the
surface of RBCs. They are called agglutinogens.
• Blood contains antibodies in plasma. These are called
agglutinins.
• These are 4 blood groups in this system A, B, AB and O.
• 45% of the people belong to O group. Persons having AB group
are called Universal recipients. Persons having O group are
called universal donors.
12. ABO System:
Group Agglutinogens Agglutinin
A A Anti B (β)
B B Anti A (α )
AB Both A and B Nil
O Nil Anti A and Anti B
Note: ABO incompatibility: When mismatched blood is transfused to a
person, serious reactions can occur resulting in death of the person.
The affected person develops hemolysis resulting in shock and renal failure.
13. Rh system:
• It is also an important system of blood grouping. The term
Rh is derived from Rhesus factor since the original
discovery was made in Rhesus monkeys.
• There are 6 agglutinogen is Rh system. They are C, D, E,
c, d, e. Out of the 6 only D agglutinogen is potent and
therefore Rh group is described only in relation to D
agglutinogen.
• Individuals having D agglutinogen are said to be Rh+ve
and individuals not having D agglutinogen are said to be
Rh-ve.
• About 85% of the population is Rh +ve and 15% of the
population is Rh –ve.
14. Clinical Importance of Rh incompatibility:
• Rh Incompatibility:
An Rh –ve individual transfused with Rh +ve blood
develops anti Rh agglutinins slowly. If this person is later
exposed to Rh+ve blood then severe transfusion reactions occur.
15. Erythroblastosis foetalis:
• This is a disease of neonates. If Rh+ve baby is born to an Rh-ve
mother some foetal erythrocytes pass to the mother during
childbirth. This produces anti D antibodies in the mother. In the
next pregnancy, if the foetus is Rh +ve these antibodies from the
mother will destroy foetal erythrocytes leading to hemolytic
disease of the newborn.
• Clinical Features: The foetus will be jaundiced, anemic, liver
and spleen are enlarged. Increased concentration of bilirubin in
the brain tissues can damage the nerve cells leading to
kernicterus. In severe form it presents as hydrops foetalis.
16. Cont…
Prevention: Administration of anti D antibodies to the
mother soon after delivery of the first child. This
causes destruction of Rh +ve foetal cells in maternal
blood.
Treatment: Replacement of blood of the newborn with
Rh-ve blood repeatedly during the first few weeks.
About 400 ml of Rh-ve blood is infused and at the
same time equal amounts of Rh+ve neonatal blood is
removed.
17. Uses of Blood grouping and Rh Typing:
Proper blood transfusion.
Medico legal importance – Paternity testing, Crime
detection.
Genetic studies.
Study the influence of blood group in evaluation of
diseases.
18. BLOOD TRANSFUSION:
It is a procedure in which blood collected
from the donor is transfused to the
recipient.
19. Cont…
Indications
• Sudden blood loss due to
accidents.
• During major surgeries.
• Patients with bleeding
disorders.
• Patients with severe burns.
• Patients with severe anemia,
thalassemia and leukemia.
Collection and storage of Blood
• Blood is collected from a
healthy donor free of all
infectious diseases like HIV,
hepatitis, malaria and Syphilis.
• It is collected under strict
aseptic precautions and mixed
with anti-coagulant (acid citrate
dextrose).
• This is stored at 2-4⁰C in blood
bank.
• The stored blood has to be used
within 3 weeks from the time
of its collection.
20. Precautions during Blood Transfusion:
• Temperature of the blood to be transfused must be
brought to room temperature.
• Transfusion should be done under strict aseptic
precautions.
• Transfusion must be very slow since rapid infusion can
lead to excessive load on the heart resulting in cardiac
failure.
22. Cont…
1. Blood grouping: Saline suspension of RBC is mixed
with anti A, anti B and anti D sera. Presence or
absence of agglutination will help to identify the
blood group.
2. Cross matching: Erythrocytes of the donor are
matched with serum of recipient in major cross
matching. In minor cross matching, erythrocyte of
recipient is matched with serum of the donor.
23. Hazards of Blood Transfusion:
• List some of the hazards of blood transfusion and nurses
role?
