Blood Donation lecture part 2

Introduction to Blood Donation

  • Blood Donation Requirement: Individuals cannot donate blood if they have certain illnesses, are on medications like aspirin, or have had risky behaviors.

  • Historical Context: Previously, barcoded labels for blood types were unknown to donors; labels indicated whether the blood was safe for transfusion.

  • Testing for Safety: All blood products undergo testing to ensure safety for transfusion.

Types of Blood Donations

1. Allogeneic (Homologous) Donations

  - Definition: Blood donated by one person to be used by another.
  - Function: Majority of blood collected for inventory which doctors will match based on needs.

2. Autologous Donations

  - Definition: Blood donated by an individual for their own future use.
  - Process: Donors can donate blood before surgeries (usually 3 units max, 3-5 days before surgery).
  - Expiry: Blood must be used before the 42-day shelf life, hence donations must be scheduled close to surgery date.
  - Risks: Decreases the donor's hemoglobin levels; if hemoglobin is too low (e.g., 110 g/L after multiple donations), further donations are prohibited.

3. Directed Donations

  - Definition: Blood donated for a specific recipient (e.g., family member).
  - Concerns: Possible issues with HLA antigens leading to Graft-Versus-Host Disease (GVHD). Risk is higher if blood is donated from parents to children due to antigen similarity.
  - Requirements: Donors must still meet standard health criteria as any blood donor.

4. Designated Donors

  - Definition: Individuals with specific antigen negative blood types donating for patients who need such specific blood.
  - Example: A donor known to be negative for the little e antigen may donate for a sibling with an antibody against that antigen.

Testing and Processing of Blood

  • Blood Collection Process: Blood collected in a sealed environment with a guarantee against contamination (closed system).

  • Separation Process: Blood is processed to create red blood cells, plasma, and platelets via centrifugation and filtration.

  • **Testing Procedures:
      - Donors undergo screening and questionnaires regarding health history.
      - Blood samples tested for various viruses (e.g., HIV, hepatitis) and blood type characteristics.

  • Leukocyte Reduction: Blood is filtered to remove white blood cells to eliminate the risk of CMV/West Nile virus transmission.

Specific Blood Products

1. Platelets and Plasma

  • Platelets: Essential for clotting; must be stored at room temperature to remain viable.
      - Apheresis Platelets: Blood collected from donors using apheresis machines to extract single components, with returned red cells.

  • Cryoprecipitate: Derived from plasma, useful for patients with hemophilia; historically used until synthetic options (e.g., recombinant factors).
      - Production of Cryo: Plasma thawed, then spun down to separate cryoprecipitate used for treating fibrinogen deficiencies.

2. Whole Blood Processing

  • Whole Blood: Initially collected as whole blood, which later gets processed into useful components (e.g., RBC, plasma, platelets).
      - Infusion Timing: Transfusion of blood components must follow strict expiry dates and usage criteria.

Donation and Processing Guidelines

  • Collection Duration: Blood should be fully collected within 15 minutes; if exceeded, the unit is discarded.

  • Safety Measures: Ensuring a sterile environment during donation to prevent infections. Donation requires donor to remain seated comfortably to avoid fainting post-donation.

  • Documentation: Clear labeling of units with donation numbers, expiry dates, and component specifics to avoid errors in transfusion.

Conclusion

  • Voluntary Donation System: In Canada, blood donations are voluntary, without compensation to ensure the integrity of the blood supply. Recent trends offer plasma donation compensation, but strict oversight is in place to ensure donor safety.

Summary of Key Terms and Concepts

  • HLA Match (Human Leukocyte Antigen): Matching of donor and recipient genes to reduce risk of complications.

  • GVHD (Graft Versus Host Disease): A potential disease when donor cells attack recipient's tissues, especially in closely related individuals.

  • Transfusion Requirements: Clinical criteria set for when transfusions are necessary based on surgery type and blood type compatibility.