Transcript BLOOD GROUPS

BLOOD GROUPS
 Blood groups are classified according
to antigens on the membrane of RBCs
called “Agglutinogen”, which are
glycoprotein.
 The plasma may contain antibodies
called agglutinins.
 Two main systems of antigens and
hence grouping are the ABO and Rh
systems.
ABO system
 1- Group (A): 40% of population,
RBCs has A Agglutinogens and the
plasma contains anti B antibodies. It
may be homozygous (AA) or
heterozygous (AO).
 2- Group (B): 10% of population,
RBCs have B antigen and plasma
contain anti A it may be homozygous
(BB) or heterozygous (BO).
ABO system to be continued
 3- Group (AB): 5% of population,
RBCs has both agglutinogens A + B,
the plasma does not contain
agglutinins.
 4- Group (O): 45% of population,
RBCs has no agglutinogens, but the
plasma contains both agglutinins
Anti A + Anti B.
Rh System
 People are classified according
to the presence or absence of
Rhesus antigens (most common
type D) into Rh+ve with D
antigen 85% and Rh-ve without
D antigen 15%.
Importance of Blood Groups:
1-Medicolegal importance:
Disputed parenthood.
Regarding blood group inheritance 2 antigens are
inherited from both father and mother.
These antigens determine the group.
The A + B antigens are dominant while the O one is
recessive.
 In group A (phenotype A) the genotype may be AA
or AO.
 In Group B may be (BB or BO).
 In Group AB and O (AB or O).
 Blood grouping is a good -ve test in disputed
parenthood
2- Blood Transfusion
 If transfused blood is incompatible
usually
the
donor
RBCs
are
agglutinated
by recipient plasma as
the donor’s serum is diluted in recipient
blood.
- Group O: is the universal donor (no
agglutinogens).
- Group AB: is the universal recipient
(no agglutinins).
3-). Importance of Rh factor: (Erythroblastosis Fetalis)
 The disease occurs when an Rhve mother carries an Rh+ve fetus,
small amounts of fetal blood leak
into the maternal circulation at
the time of delivery, thus the
mother will produce Anti D
agglutinins.
(Erythroblastosis Fetalis) to be cont.
 During the next pregnancy the mother
agglutinins cross the placenta (IgG) to an
Rh+ve fetus causing hemolysis of fetal
RBCs and may lead to:
 Anemia of fetus
 Death of fetus.
 Jaundice with deposition of bile pigment in the
basal ganglia (kernicterus syndrome) as the
blood brain barrier is not developed yet
(Erythroblastosis Fetalis).
(Erythroblastosis Fetalis) to be cont.
 The first baby (Rh+ve) is affected in
case of maternal sensitization by:
-Previous Rh +ve blood transfusion.
- If the baby was born alive should
be treated by exchange blood
transfusion with Rh -ve group O
blood.
(Erythroblastosis Fetalis) to be cont.
 Fetal-Maternal
hemorrhage
during
pregnancy.
 This disease can be prevented by avoiding
Rh+ve blood transfusion to Rh-ve females,
and if pregnancy and labor happened an
anti-D antibodies are given to neutralize the
D antigens of the Rh +ve fetal cells and
prevent sensitization of the mother.
BLOOD TRANSFUSION
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Indications
If the whole blood or any of its components is
deficient blood transfusion is indicated as in case of;
- Acute hemorrhage.
- Severe anemia.
- Agranulocytosis.
- Thrombocytopenia.
- Hemophilia.
However, if one element only is deficient it is
preferable to give this particular element e.g. packed
RBCs and human plasma transfusions.
Precautions
 - Blood should be compatible (ABO and
Rh) assured by cross matching test.
 - Blood should be free from contamination.
 - Blood should be free from blood born
diseases.
 - Blood should be fresh (less than 2 weeks
storage).
 - High hemoglobin content.
Precautions to be cont.
 Blood is stored at 4oC and added to:
- Sodium citrate as an anticoagulant.
- Dextrose as a nutrient for cells.
- Citric acid to reduce the pH.
- Storage lead to decrease in platelets,
coagulation factors VII, VIII, IX and
dextrose, while there is increase in lactic
acid content, K and haemoglobin released
from haemolysed RBCs.
Complications
 The donor may suffer from anemia in repeated
donation and shock in excessive volume donation.
The recipient may suffer from:
 1- Mechanical effect:
- Air or fat embolism.
- Dislodgement of a thrombus.
 2- Infective complications:
E.g. infective hepatitis, AIDS or Malaria.
 3- Physiological complications:
- Overloading in excessive transfusion leading to
heart failure.
- Pyrogenic reaction i.e. fevers.
 4- Incompatibility complications
 Agglutinated RBCs may block small vessels causing
severe pain, or haemolysis follows i.e., liberation of
hemoglobin, K+ and toxins into plasma.
a) Hemoglobin liberation will cause:
- increased blood viscosity leading to heart failure.
- conversion into bile causing jaundice.
- precipitate in renal tubules as acid haematin
causing renal
failure.
- hypoxia.
 b) K+ causes arrhythmia.
 c) Toxic substances cause powerful vasoconstriction
of renal vessels causing acute renal failure.