blood physiology practical 1

Phase II Medicine- Blood Module - May 2008

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BLOOD PHYSIOLOGYPractical 1

BLOOD GROUPS


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Objectives• Describe the clinical significance of determination of blood

groups.• Name the blood groups of ABO & Rh system.• Describe the principle of determination of blood groups.• Determine blood groups by using anti-A and anti-B antisera.• Mention the common indications of blood transfusion.• List the common hazards of transfusion.• Name the diseases transmitted by blood transfusion.• Describe the concept of universal donor and universal recipient.• Describe the cause of erythroblastosis fetalis.


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Clinical significance of determination of blood groups

• At least 30 commonly occurring antigens (Ag) have been found on the cell membrane of RBCs.

• These can cause Ag-Ab reaction if mixed with plasma that contain antibodies (Ab) against these Ag.

• 2 groups of Ag can cause transfusion reactions more than others: ABO and Rh systems.


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ABO Blood GroupsA and B Antigens- Agglutinogens


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ABO Blood GroupsRelative frequency of different blood types:

• O 47%

• A 41%

• B 9%

• AB 3%


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Agglutinins

Blood type Agglutinogen on RBC

Agglutinin in plasma

A A Anti-B

B B Anti-A

AB A and B None

O None Anti-A and Anti-B


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Rh Blood Type• If type D antigen is present on RBC Rh

+ve• Differences between ABO and Rh Ab?• Anti-Rh antibodies are not naturally

occurring Ab.• Previous exposure to Rh antigen is required.

• Rh +ve blood transfusion.• Rh –ve women pregnant with Rh +ve baby.

• Anti-Rh Ab can cross the placenta.


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Blood Grouping

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Blood grouping, showing agglutination of cells of the different blood types with anti-A or anti-B agglutinins in the sera

Red blood cell types

Anti-A serum Anti B serum

O - -

A + -

B - +

AB + +


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BLOOD TRANSFUSIONS


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Blood Transfusion

• Indications.• Types:

–Heterologus–Autologous


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Universal Donor.

• Most hospitals have available group O negative blood for use in extreme emergency situations.

• Group O negative is considered as universal donor.


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Transfusion Reactions resulting from mismatched blood types

• Agglutination and delayed hemolysis of donor’s RBC (or immediate intravascular hemolysis)→ Jaundice


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20Phase II Medicine- Blood Module - May 2008

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Common Hazards of Blood Transfusion

• Acute transfusion reactions occurring within 72 hours:

– Immunological reactions :

• Haemolytic transfusion reaction• Allergic reactions eg. urticarial reaction

– Non immunological reaction: Circulatory overload

• Delayed transfusion reactions occurring after 72 hours:– Iron overload– Renal tubular blockage by haemoglobin– Renal failure



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Diseases transmitted by blood transfusion

• Viral hepatitis

• HIV / AIDS

• Other transmissible diseases are syphilis, malaria, CMV etc.,

What do you do to prevent this?


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Pre-transfusion Tests

• For a safe blood transfusion, the following tests are done:– Blood grouping

– Cross-matching



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X-matching• Once patient’s blood group is known, donor

blood of the same ABO and Rh type is selected.

• Possible donor RBC’s are mixed with the recipient’s serum. If no agglutination, no Ab in recipient blood will attack donor’s RBCs.

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Haemolytic Disease of the Newborn (HDN)

• Rh incompatibility Erythroblastosis Fetalis (HDN).

• Rh –ve lady marrying Rh+ve man.• If baby is Rh+ve, fetal RBC leaks to maternal

circulation during placental separation (delivery or abortion).

• Mother starts to make anti-Rh Ab.• Next pregnancy with Rh+ve baby anti-Rh Ab

pass to baby and cause agglutination and hemolysis of his RBC.


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HDN• Clinical picture:

• Anemia→ Jaundice

• Hepatosplenomegaly

• Kernicterus (mental

impairment due to precipitation of bilirubin in brain cells)


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Prevention• Anti-D antibodies (RhoGam) injection

given to Rh –ve mothers after delivery of Rh +ve baby.


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blood physiology practical 1

Documents

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blood groupsphase

blood transfusionindications

blood physiologypractical

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blood transfusionsphase

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