Stored blood undergoes several chemical changes over time, impacting its viability for transfusion. These changes primarily involve the breakdown of red blood cells, leading to:
1. Decrease in Red Blood Cell Viability:
- Hemolysis: Red blood cells (RBCs) start to break down, releasing hemoglobin into the plasma. This process, known as hemolysis, reduces the oxygen-carrying capacity of the blood.
- Metabolic Changes: The stored RBCs continue to metabolize glucose, consuming ATP and generating lactic acid. This acidification of the blood can further damage the cells.
2. Alterations in Plasma Composition:
- Decreased pH: The accumulation of lactic acid from RBC metabolism lowers the pH of the blood, making it more acidic.
- Increased Potassium: As RBCs break down, potassium is released into the plasma, potentially leading to hyperkalemia in the recipient.
- Decreased Glucose: The stored RBCs consume glucose, leading to a decrease in blood sugar levels.
3. Changes in Blood Components:
- Platelet Aggregation: Platelets, essential for blood clotting, start to aggregate and lose their function over time.
- Coagulation Factors: Some coagulation factors, crucial for blood clotting, become less active during storage.
4. Growth of Bacteria:
- Bacterial Contamination: Although blood is usually collected under sterile conditions, bacterial contamination can occur during storage, especially if the blood bag is damaged.
5. Formation of Microparticles:
- Microparticle Formation: Stored blood can develop microparticles, small fragments of cells that can activate the immune system and potentially cause complications in the recipient.
Understanding these chemical changes is crucial for optimizing blood storage conditions and ensuring the safety and efficacy of blood transfusions. Blood banks employ various techniques to minimize these changes, such as using specialized storage solutions and maintaining optimal temperature and humidity.
