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BLOOD PHYSIOLOGY Practical 1. BLOOD GROUPS. 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.
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BLOOD PHYSIOLOGYPractical 1 BLOOD GROUPS Phase II Medicine- Blood Module - May 2008
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. Phase II Medicine- Blood Module - May 2008
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. Phase II Medicine- Blood Module - May 2008
ABO Blood GroupsA and B Antigens- Agglutinogens Phase II Medicine- Blood Module - May 2008
ABO Blood Groups • Relative frequency of different blood types: • O 47% • A 41% • B 9% • AB 3% Phase II Medicine- Blood Module - May 2008
Agglutinins Phase II Medicine- Blood Module - May 2008
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. Phase II Medicine- Blood Module - May 2008
Blood Grouping Phase II Medicine- Blood Module - May 2008
Blood grouping, showing agglutination of cells of the different blood types with anti-A or anti-B agglutinins in the sera
BLOOD TRANSFUSIONS Phase II Medicine- Blood Module - May 2008
Blood Transfusion • Indications. • Types: • Heterologus • Autologous Phase II Medicine- Blood Module - May 2008
Universal Donor. • Most hospitals have available group O negative blood for use in extreme emergency situations. • Group O negative is considered as universal donor. Phase II Medicine- Blood Module - May 2008
Transfusion Reactions resulting from mismatched blood types • Agglutination and delayed hemolysis of donor’s RBC (or immediate intravascular hemolysis)→ Jaundice Phase II Medicine- Blood Module - May 2008
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 Phase II Medicine- Blood Module - May 2008 Phase II Medicine- Blood Module - May 2008 20
Diseases transmitted by blood transfusion • Viral hepatitis • HIV / AIDS • Other transmissible diseases are syphilis, malaria, CMV etc., • What do you do to prevent this? Phase II Medicine- Blood Module - May 2008 Phase II Medicine- Blood Module - May 2008 21
Pre-transfusion Tests • For a safe blood transfusion, the following tests are done: • Blood grouping • Cross-matching Phase II Medicine- Blood Module - May 2008
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. Phase II Medicine- Blood Module - May 2008 Phase II Medicine- Blood Module - May 2008 23
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.
HDN • Clinical picture: • Anemia→ Jaundice • Hepatosplenomegaly • Kernicterus (mental impairment due to precipitation of bilirubin in brain cells) Phase II Medicine- Blood Module - May 2008
Prevention • Anti-D antibodies (RhoGam) injection given to Rh –ve mothers after delivery of Rh +ve baby. Phase II Medicine- Blood Module - May 2008