Lecture Notes: Blood Transfusions

Cardiovascular System and Blood Loss

• Functions:
  • Minimize effects of blood loss by:
    1. Reducing blood volume sent to affected vessels.
    2. Increasing red blood cell production (erythropoiesis).
• Blood Loss Effects:
  • 15-30% loss: Causes pallor and weakness.

  • 30% loss: Potentially fatal; can lead to shock and death.

Blood Volume Replacement

• In case of massive hemorrhage:
  • Rapid replacement with normal saline or electrolyte solutions like Ringer’s solution to mimic plasma composition.
  • These solutions restore volume but not oxygen-carrying capacity.

Blood Transfusions

• Types:
  • Whole Blood Transfusions: Rare, used for massive blood loss.
  • Packed Red Blood Cells (PRBCs): Common, with plasma and leukocytes removed.
• Blood Banks:
  • Blood is separated into components.
  • Shelf life of blood is about 35 days.

Blood Typing and Compatibility

• Importance:
  • Blood groups must be determined to avoid fatal transfusion reactions.
  • Antigens on red blood cells determine blood group.
  • Mismatched transfusions can cause severe immune responses.

Antigens and Immune Response

• Antigens (Agglutinogens):
  • Perceived as foreign and can trigger an immune response.
  • Antigens on red blood cells cause clumping if transfused incorrectly.
• Human Blood Groups:
  • At least 30 antigens on red blood cells.
  • Some antigens (MNS, Duffy, Kell, Lewis) are weak agglutinogens.
  • Most significant for transfusions are ABO and Rh blood groups.

ABO Blood Groups

• Types:
  • Based on presence/absence of antigens A and B.
  • Blood types: A, B, AB, O.
  • Type O: No A or B antigens (universal donor).
  • Type AB: Both A and B antigens (universal recipient).

Antibodies and Immune Reaction

• Formation:
  • Antibodies against non-present antigens form after 2 months of age.
  • Mismatched blood transfusions cause agglutination and immune response.

Rh Blood Groups

• Antigens:
  • Rh factor includes several antigens (C, D, E).
  • Rh positive (85% of Americans) have Rh antigen D.
  • Rh negative individuals form antibodies only upon exposure to Rh positive blood.

Hemolytic Disease of the Newborn

• Risk Factors:
  • Occurs when Rh-negative mother carries Rh-positive fetus.
  • Mother's antibodies may attack fetal red blood cells in subsequent pregnancies.
• Prevention:
  • Treatment with RhoGAM to prevent antibody formation.

Transfusion Reactions

• Causes:
  • Mismatched blood transfusion.
  • Donor red blood cells attacked by recipient's plasma antibodies.
  • Can cause clumping, reduced blood flow, and renal failure.
• Symptoms:
  • Fever, chills, low blood pressure, rapid heart rate, nausea, vomiting.
• Treatment:
  • Prevent kidney damage by increasing fluid intake and using diuretics.

Blood Typing and Crossmatching

• Process:
  • Blood mixed with antibodies against common antigens to check for agglutination.
  • Crossmatching involves mixing donor and recipient blood samples to ensure compatibility.