Iron Content in Packed Red Blood Cell Units
One unit of packed red blood cells contains approximately 200-250 mg of elemental iron. 1
Understanding Iron Content in Blood Products
- A standard unit of packed red blood cells (pRBCs) contains 200-250 mg of elemental iron, which accumulates in the body as there is no active excretion mechanism 1
- The volume of a typical pRBC unit ranges from 180-330 ml, with hyperpacked units having volumes around 162-180 ml and conventional units around 270-330 ml 2, 3
- The iron in pRBC units is primarily contained within the hemoglobin of red blood cells, which is the main iron-containing component in blood 4
Clinical Implications of Iron Content in Transfusions
- One unit of packed red cells is estimated to increase hemoglobin levels by approximately 1 g/dL in an average-sized adult who is not actively bleeding 1
- The average increase in hematocrit per liter of packed red blood cells transfused is about 6.4% ± 4.1%, which translates to approximately 1.9% ± 1.2% increase in hematocrit per unit of blood 3
- Chronic blood transfusion therapy can lead to significant iron overload over time, as each unit contributes 200-250 mg of iron that cannot be actively excreted 1
Iron Distribution and Metabolism
- In adults, red blood cells in circulation contain approximately 35 mg/kg of iron, representing the largest functional iron compartment in the body 1
- The average lifespan of a transfused red blood cell is approximately 100-110 days 1
- Iron from transfused red cells is not immediately available for erythropoiesis but must first be recycled through the reticuloendothelial system 1
Clinical Considerations for Transfusion
- A common misconception is that packed red cell transfusions immediately reverse iron deficiency; however, the iron from transfused cells only becomes available after the cells are broken down 1
- In patients with anemia of inflammation, iron recycling may be further delayed due to sequestration in macrophages 1
- For patients requiring iron repletion, intravenous iron therapy may be needed in addition to transfusion, particularly in the 90 days following transfusion 1
Monitoring Iron Status After Transfusions
- Serum ferritin can be a poor marker for accurately assessing iron overload in patients receiving chronic transfusions and should not be used as the sole guide for chelation therapy 5
- In patients receiving chronic transfusions, the quantitative iron load correlates more strongly with the duration of transfusion therapy than with serum ferritin levels 5
- Patients receiving multiple transfusions should be monitored for signs of iron overload, which can lead to organ damage, particularly in the liver, heart, and endocrine organs 1