From the Guidelines
A unit of blood is estimated to increase hemoglobin levels by approximately 1 g/dL in an average-sized adult who is not bleeding. This estimate is based on the study published in the American Journal of Hematology in 2014 1. The increase in hemoglobin levels can vary depending on several factors, including the patient's size and the volume of the blood unit.
- The volume of a standard unit of packed red blood cells is typically around 300 mL, which contains concentrated hemoglobin within intact erythrocytes.
- These erythrocytes immediately contribute to oxygen-carrying capacity upon transfusion, with the effect measurable within 15 minutes to 1 hour after transfusion completion.
- However, patients with active bleeding may show less of an increase in hemoglobin levels due to ongoing blood loss counteracting the transfused volume.
- For accurate assessment of the hemoglobin response, a post-transfusion complete blood count should be obtained after allowing time for equilibration, typically 1-2 hours after transfusion completion, as noted in the study 1.
From the Research
Increase in Hemoglobin due to Blood Transfusion
- Each unit of packed red blood cells (PRBCs) is expected to raise circulating hemoglobin (HGB) by approximately 1 g/dL 2.
- The increase in hemoglobin is influenced by the starting hemoglobin level, with lower pre-transfusion HGB associated with a larger increase in HGB 2.
- The number of units of PRBCs given also affects the increase in hemoglobin, with one unit likely to be sufficient for most HGB targets after subarachnoid hemorrhage, especially in patients with more severe anemia 2.
Comparison with Other Studies
- Other studies focus on the management of anemia using erythropoiesis-stimulating agents (ESAs) and iron therapy, rather than blood transfusion 3, 4, 5, 6.
- These studies do not provide direct information on the increase in hemoglobin due to blood transfusion, but rather explore alternative strategies for managing anemia.