From the Guidelines
One unit of packed red blood cells (PRBCs) typically contains approximately 300 mL of volume, as stated in the most recent and highest quality study 1. This includes about 200-250 mL of red blood cells and a small amount of preservative solution. The exact volume may vary slightly between blood banks and preparation methods. PRBCs are created by removing most of the plasma from whole blood, resulting in a concentrated product with a hematocrit of about 50-80%, compared to the normal human hematocrit of around 40-45% 1. Some key points to consider when administering PRBCs include:
- The concentration of PRBCs allows for the delivery of oxygen-carrying capacity without the additional volume of plasma, making it useful for patients who need red blood cells but not necessarily the extra fluid volume.
- Each unit of PRBCs is expected to raise the hemoglobin by approximately 1 g/dL or the hematocrit by about 3% in an average-sized adult patient, though individual responses may vary based on factors such as patient size, ongoing blood loss, or destruction of transfused cells 1.
- The benefits and risks of red cell transfusion have been well studied, and it is essential to consider these factors when deciding whether to administer PRBCs to a patient 2.
From the Research
Volume of Packed Red Blood Cells
- The volume of 1 unit of packed red blood cells is approximately 300 mL, as mentioned in the study 3.
- This study analyzed the post-transfusion alterations in hematocrit from 61 independent transfusions in 48 different pelvic fracture patients and found that the average increase in hematocrit per liter of packed red blood cells transfused was 6.4% +/- 4.1% 3.
- If 1 "unit" of packed red blood cells is approximately 300 mL, this becomes a change of hematocrit of 1.9% +/- 1.2% per "unit" of blood 3.
Comparison with Other Studies
- Other studies, such as 4 and 5, focused on the hemoglobin content of packed red blood cells and its impact on transfusion efficacy, but did not specifically address the volume of 1 unit of packed red blood cells.
- Study 6 discussed the safety and indications of packed red blood cell transfusions, but did not provide information on the volume of 1 unit.
- Study 7 reported a case of post-transfusion encephalopathy in a pediatric patient, but did not address the volume of packed red blood cells.