Iron Content in Packed Red Blood Cells
One unit of packed red blood cells (PRBCs) contains approximately 200-250 mg of iron. 1
Detailed Iron Content Information
Packed red blood cells have a significantly higher concentration of iron compared to whole blood:
- Whole blood contains about 0.47 mg/mL of iron
- Pure RBC concentrates contain about 1.16 mg/mL of iron 1
- A standard unit of PRBCs typically has a volume of 180-330 mL 2
This iron content is clinically significant, particularly when considering multiple transfusions over time. After 20-25 units of blood transfusions, patients can develop iron overload 1, which has important implications for patient management.
Clinical Implications of Iron Content in PRBCs
Iron Overload Risk
Iron overload from repeated transfusions can lead to:
- Cardiac iron deposits (seen in approximately 60% of patients who receive >75 units) 1
- Liver damage with portal fibrosis (7-26 times normal iron levels) 1
- Impaired cardiac left ventricular function
- Glucose intolerance
- Limited pituitary function 1
Common Misconception
A common misconception is that transfused red blood cells immediately reverse iron deficiency. However:
- The average lifespan of transfused red cells is approximately 100-110 days
- The iron from transfused cells is not immediately available for erythropoiesis
- In inflammatory conditions, iron may take even longer to be recycled due to sequestration in macrophages 1
Transfusion Effect on Hemoglobin/Hematocrit
- One unit of PRBCs typically increases hemoglobin by approximately 1 g/dL in an average-sized adult who is not actively bleeding 1
- The hematocrit increase is approximately 3% per unit, though studies show variability with an average increase of 1.9% ± 1.2% per unit 3
Iron Monitoring in Transfusion-Dependent Patients
For patients receiving multiple transfusions, monitoring iron status becomes important:
- Consider iron chelation therapy in transfusion-dependent patients after approximately 25 units of red cells when serum ferritin exceeds 1000 ng/mL 1
- Magnetic resonance imaging (T2*) can assess iron loading in the liver and cardiac tissue 1
- Monitoring serum ferritin and transferrin saturation can help assess iron overload 1
Summary
The 200-250 mg of iron in each unit of PRBCs is clinically significant, especially in patients requiring multiple transfusions. While this iron content helps address anemia in the short term, the cumulative iron load from repeated transfusions requires monitoring and potentially iron chelation therapy to prevent organ damage from iron overload.