Overview
This lecture covers blood transfusions, including the separation of blood components, matching blood types, transfusion reactions, and the process of hemostasis (stopping bleeding).
Blood Transfusion Basics
- A transfusion is the transfer of blood components from a donor to a recipient.
- Modern practice separates blood into components: red blood cells, white blood cells, plasma, platelets, etc.
- Only needed components are given to patients, making transfusions safer and more efficient.
- Donated blood is always tested and typed before use.
Blood Type Compatibility and Transfusion Reactions
- Blood type mismatch can cause a transfusion reaction due to recipient antibodies attacking donor red blood cells.
- Antibody binding leads to agglutination (clumping) of red blood cells, which can block small blood vessels.
- Clumped red cells may rupture, releasing hemoglobin, which is toxic to kidneys and can cause acute injury or death.
- Blocked blood flow may result in heart attack, stroke, or embolism; loss of red cells can cause hypoxia (low blood oxygen).
Blood Types and Transfusion Rules
- Blood type depends on antigens present on red blood cell surfaces (A, B, RhD).
- Plasma contains antibodies against antigens not present on the individual's own red cells.
- Type O blood has no A or B antigens and is the universal donor.
- Type AB blood has no anti-A or anti-B antibodies and is the universal recipient.
- People with negative RhD blood must receive negative blood to avoid developing anti-RhD antibodies.
Hemostasis (Stopping Bleeding)
- Hemostasis is the process that stops bleeding from damaged blood vessels.
- It involves three steps: vasoconstriction, formation of a platelet plug, and coagulation (clotting).
- Vasoconstriction is the contraction of vessel smooth muscle to reduce blood flow after injury.
- The degree of vasoconstriction is greater with more severe injury and occurs mainly in small vessels.
- Triggers include direct injury, chemicals from endothelial cells and platelets, and local pain reflexes.
Key Terms & Definitions
- Transfusion — transfer of blood or blood products from one person to another.
- Antigen — molecule on red blood cells that determines blood type.
- Antibody — protein in plasma that attacks non-self antigens.
- Agglutination — clumping of red blood cells during a transfusion reaction.
- Hemostasis — the process of stopping bleeding.
- Vasoconstriction — narrowing of blood vessels to reduce blood flow.
- Coagulation — process of blood clot formation.
Action Items / Next Steps
- Study blood type compatibility charts in detail.
- Review the three steps of hemostasis.
- Prepare for quiz on transfusion reactions and blood component functions.