Archive for the ‘ L3-Blood Transfusion ’ Category

L3- Blood Transfusion

Why Blood is the Gift of Life?

•No other substitute for blood

•Human Blood is the only substitute for those who need blood

Do U Know?

•Transfer of blood was known since 2 hundreds  years but it only became safer

•Since 1901 when the Austrian Karl Landsteiner who discovered blood groups

•For his discovery, Landsteiner was awarded NOBEL PRIZE in Physiology 1930

Why Blood Grouping is a prerequisite for a safe Blood Transfusion?

•Blood groups depends on presence or absence of certain protein molecules called antigens & antibodies

•So far, more than 20 genetically determined blood groups are known

•However, the most important for blood transfusion are ABO & Rh systems

ABO System

•Is classified into A, B, AB & O according to presence of certain glycoprotein antigen (agglutinogen) on surface of RBCs

•Whereas, in plasma certain non corresponding antibodies (agglutinins) exist

•Presence of agglutinogen with its corresponding agglutinin will induce Ag-Ab reaction (agglutination)

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•Plasma agglutinins: Anti-A & Anti B are of IgM type that usually do not cross placenta

•They are naturally occurring because they are formed without previous exposure to foreign blood cells

•At birth, their level is almost zero but start to increase reaching maximum at 8-10 years

•Used for determination of blood groups • •

Rh System

•Rh-positive person (Rh+): with Rhesus antigan (D, C, E) present on surface of his RBCs (D is the most antigenic)

•(Rh-)person:  no antigen on RBCs

•No antibodies exist in plasma without prior exposure to antigen

•Anti-D (antibodies against D antigen) is formed in (Rh-) when he receives Rh+ blood for 1st time

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•On a 2nd exposure to Rh+ blood, previously formed anti-D will agglutinate with donor RBCs (sever Ag-Ab reaction) causing haemolysis of RBCs

•Anti-D antibodies are IgG that can cross placenta

•Therefore, if an Rh- mother is exposed to some of her foetus Rh+ blood (during birth process) will form Anti-D •On 2nd pregnancy, these antibodies will cross placenta & agglutinate with RBCs of foetus if he is Rh+ → haemolysis of foetal RBCs (Erythroblastosis foetalis).

Erythroblastosis Foetalis

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What are Antibodies?
Revise your Immunology Lectures of life Cycle Semester

•Ab are γ immunoglobulins that are formed due to exposure to foreign antigen (immune stimulus)

•~ 20% of plasma proteins

•Produced from processed B lymphocytes that are converted to plasma cells upon exposure to specific antigen

•Each consists of 2 identical light chains & 2 identical heavy chains

•There are 5 classes of antibodies (named after heavy chain; alpha (A), delta (D), gamma (G)

Basic Structure & 5 Classes of Ab

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Ag-Ab reaction

•Antibodies react against antigen inactivating it by the following reactions:

1.Agglutination; formation of a cellular clump

2.Precipitation; precipitation of an insoluble Ag-Ab complex

3.Neutralization; rendering the Ag intoxic

4.Lysis; degradation of cellular components of Ag by Ab

Ag-Ab reaction in incompatible Blood Transfusion;
RBC Agglutination

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Blood Transfusion:

Giving & Receiving

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Indications

Loss of blood

1.Surgery

2.accidents

3.Burns

Blood disease

1.Leukopenia

2.Anaemia

3.Thrombocytopenia

4.Hypoproteinaemia

5.Hemophilia

Erythroblastosis foetalis

Content

1•whole blood (anaemia, leukopenia, Hg)

2•individual components:

RBCs → (anaemia)

Platelets → (low platelet count, bleeding)

Fresh frozen Plasma (FFP)→(within 8 hours from collection, all clotting factors)

Precautions prior to Transfusion

•Blood Typing

•Major Cross Matching

•Hb content of transfused blood is not <90%

•Free from infectious diseases

•Fresh non frozen blood (<21days storage, stored at 4ºC)

1 Blood Typing

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2 Major Cross-Matching

•Donor  RBCs are tested with recipient serum

•to detect unexpected recipient antibodies

•It is rare that recipient RBCs are agglutinated by donor antibodies because donor antibodies are diluted with greater plasma volume of recipient

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•However, if too large volume of donor blood is transfused, agglutination could occur between donor antibodies & recipient RBCs

•Therefore, the concept of universal donor for O blood group is applicable only for transfusing small volume of blood

Hazards of Blood Transfusion

1-Transfusion Reaction due to incompatible blood

2-Allergic reactions caused by leucocytes & platelets

3-Transmission of infectious diseases; viral hepatitis, AIDS

4-Too large volume (>1L)→ •circulatory overload

•Hypothermia

•Hyperkalamia

•Citrate used as anticoagulant → hypocalcaemia + alkalosis

Transfusion Reaction;

Incompatible Blood Transfusion

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Acute Transfusion Reaction

•1 in 6000 to 25000 transfusion

•Manifestations include: chest pain, fever, red urine, disseminated intravascular coagulopathy (DIC), shock

•Death; 1 in 4

•Immediate stoppage of transfusion

Effects of Transfusion Reaction

•Blockage of blood capillaries by clumped RBCs

•Intravascular Haemolysis can lead to:

1.Release of histamine →↓ABP→ shock

2.Release of K→ hyperkalamia

3.Release of Hb →bilirubin →jaundice

4.Release of Hb→ precipitation of Hb as haematin crystals in renal tubules blocking them

5.1 & 4 can lead to Acute renal failure

Allergic Transfusion Reaction

•Caused by antibodies formed against donor’s plasma proteins

•Symptoms include itching, flushing & wheezes

•TTT by anti-histaminic •if severe; stop transfusion

In Case of Emergency

•A patient with unknown blood group & in need for immediate blood

•Transfer group O Rh- blood

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