Changes in Stored Blood
Stored blood undergoes several biochemical changes including increased H+ (acidosis), decreased 2,3-diphosphoglycerate (2,3-DPG), increased red cell fragility, increased K+, and decreased Ca2+.
Biochemical Changes During Blood Storage
Acid-Base Changes
- Stored blood becomes progressively more acidic (increased H+) due to continued glycolysis and accumulation of lactic acid in the storage medium 1
- This acidosis contributes to other biochemical changes and affects oxygen delivery capacity
2,3-DPG Changes
- 2,3-DPG levels decrease significantly during storage, reducing to zero after about 2 weeks 1
- This decrease shifts the oxygen-hemoglobin dissociation curve to the left, increasing hemoglobin's affinity for oxygen and potentially reducing oxygen delivery to tissues 1, 2
- After transfusion, 2,3-DPG levels recover to approximately 50% of normal within 6 hours and return to normal within 48 hours 1
Red Cell Membrane Changes
- Red blood cells become less flexible and more fragile during storage 3
- This increased fragility (not decreased fragility as suggested in option C) impairs their ability to navigate through the microcirculation 3
- The breakdown of red cells leads to release of hemoglobin into the storage medium (hemolysis) 4
Electrolyte Changes
- Potassium (K+) levels increase significantly during storage due to leakage from the intracellular space to the preservative fluid 1
- This is the opposite of option D, which incorrectly suggests decreased K+
- Calcium (Ca2+) levels decrease during storage due to chelation by citrate present in most RBC additives 1
- This contradicts option E, which incorrectly suggests increased Ca2+
Clinical Implications
Transfusion Considerations
- Prolonged storage is associated with increased extravascular hemolysis after transfusion 5
- Large volume or rapid transfusions of older stored blood may lead to:
Storage Duration Guidelines
- Maximum storage duration for RBCs in most countries is 42 days 3
- Current guidelines do not recommend selecting RBC units based on storage duration for routine transfusions 1
- However, some evidence suggests limiting storage to 35 days may be beneficial to reduce complications 5
Answer to the Question
Of the options presented, only option (a) increased H+ is correct. Options (b), (c), (d), and (e) are incorrect as stored blood actually shows decreased (not increased) 2,3-DPG, increased (not decreased) red cell fragility, increased (not decreased) K+, and decreased (not increased) Ca2+.