Untitled Quiz

Blood Groups

• Blood group system based on the presence/absence of antigens (agglutinogens).
• RBCs contain antigens A and/or B.
• Plasma contains antibodies (agglutinins) anti-A and/or anti-B of the IgM type.
• Four main blood groups: A, B, AB, and O.
  • A group: A antigen, anti-B antibody.
  • B group: B antigen, anti-A antibody.
  • AB group: A & B antigens, no antibodies.
  • O group: no antigens, anti-A & anti-B antibodies.
• Blood type percentages:
  • A (41%)
  • B (9%)
  • AB (3%)
  • O (47%)

Rh Factor

• Another blood group system, Rh factor, involves the D antigen.
• Rh-positive (Rh+): D antigen on RBCs (85% of white people).
• Rh-negative (Rh-): no D antigen on RBCs (15% of white people).
• No anti-Rh antibodies usually present in plasma unless exposed to Rh+ blood.
• Anti-D antibodies only form when an Rh- person is exposed to Rh+ blood.

Importance of ABO System

• Blood Transfusions:
  • Critical to cross-match donor and recipient blood types to prevent incompatibility.
  • Incompatible blood leads to destruction of donor RBCs by recipient antibodies.
  • O group is the universal donor, as it lacks antigens.
  • AB group is the universal recipient as it lacks antibodies.
• Paternity Disputes:
  • Used to exclude, not prove, paternity.
• Medico-Legal Uses:
  • To prove or disprove claims.

Importance of Rh Factor in Blood Transfusions

• An Rh-negative person receiving Rh-positive blood can develop anti-Rh antibodies.
• A second exposure to Rh-positive blood in this person causes a more severe reaction leading to agglutination and hemolysis.

Hemolytic Disease of the Newborn (Erythroblastosis Fetalis)

• Rh-negative mother and Rh-positive father can result in Rh-positive fetus.
• First pregnancy typically not affected, as Anti-D antibodies aren't produced until exposure to Rh+ blood during the pregnancy in the placenta.
• Subsequent pregnancies with an Rh+ fetus can lead to severe problems causing the fetus to die or be born with erythroblastosis fetalis (anemia, jaundice, kernicterus).
• Anti-D antibodies can be transferred across the placenta.

Treatment of Erythroblastosis Fetalis

• Replacement of fetal blood with Rh-negative blood.
• Repeated transfusions until anti-Rh antibodies disappear.

Prevention of Erythroblastosis Fetalis

• Administering anti-Rh antibodies (Rh immune globulin) to Rh-negative mothers within 72 hours of delivery or abortion.
• Prevents active antibody production by the mother.

Indications of Blood Transfusion

• Hemorrhage: Replacing lost blood.
• Specific Blood Components: RBCs (anemia), WBCs (leukopenia), platelets (thrombocytopenia), clotting factors (hemophilia).
• Erythroblastosis Fetalis: Treating severe cases in newborns.

Precautions Before Blood Transfusion

• ABO and Rh blood type compatibility check.
• Ensure hemoglobin content is sufficient (above 90%).
• Freshness (no more than 21 days since collection).
• Absence of infectious diseases.
• Proper cross-matching between donor and recipient blood.

Dangers of Blood Transfusion

• Allergies: To leukocytes and platelets.
• Disease Transmission: AIDS, viral hepatitis.
• Massive Transfusion: Heart failure, hypothermia.
• Blood Group Incompatibility:
  • Blockage of capillaries by clumped RBCs.
  • Pain in the back, joints, and chest.
  • Intravascular hemolysis: Circulatory shock, jaundice, acute renal failure.