From the Guidelines
Transfusing 1 unit of packed red blood cells is estimated to increase hemoglobin levels by 1 g/dL in an average-sized adult who is not bleeding. This estimation is based on the study published in the American Journal of Hematology in 2014 1. The increase in hemoglobin can vary depending on several factors, including the patient's body size and the quality of the transfused unit.
Key Factors Influencing Hemoglobin Increase
- Patient's body size: smaller adults or children may experience a greater increase, while larger adults may have a less pronounced increase
- Quality of the transfused unit: the volume and processing of the unit can affect the amount of hemoglobin contained in each unit of packed red blood cells
- Presence of ongoing blood loss or hemolysis: these conditions can impact the effectiveness of the transfusion in increasing hemoglobin levels Each unit of packed red blood cells contains approximately 42.5-80 g of hemoglobin, which immediately contributes to oxygen-carrying capacity in the circulation.
Clinical Considerations
- Post-transfusion hemoglobin levels should be checked approximately 15 minutes to 1 hour after completion of the transfusion to accurately assess the effect
- The benefits and risks of red cell transfusion should be carefully considered, including the risks of arterial and venous thrombosis, increased mortality risk, volume overload, transmission of viral or bacterial infection, iron overload, and transfusion-related acute lung injury 1
From the Research
Hemoglobin Increase After Transfusing 1 Unit of Packed Red Blood Cells
- The expected increase in circulating hemoglobin (HGB) after transfusing 1 unit of packed red blood cells (PRBCs) is approximately 1 g/dL 2.
- A study found that the average increase in Hb level after administrating PRBC was 1.91 ± 1.93 g/dL, with no significant differences found between change in Hb level in terms of age, gender, underlying illness, body mass index, hospitalization history, fever, and duration of hospitalization 3.
- Another study showed that hemoglobin values rapidly equilibrate after transfusion in normovolemic patients who are recovering from an acute bleeding episode, with a 24-hour increase of 22.4 +/- 6.8 g per L in hemoglobin concentration after administering 2 units of packed red cells 4.
- The increase in hemoglobin level after transfusing 1 unit of PRBC can vary depending on the patient's pre-transfusion hemoglobin level, with lower pre-transfusion HGB associated with a larger increase in HGB 2.
Factors Affecting Hemoglobin Increase
- Pre-transfusion hemoglobin level: lower pre-transfusion HGB is associated with a larger increase in HGB 2.
- Number of units of PRBCs given: the increase in HGB is directly related to the number of units transfused 2, 4.
- Patient's medical history: patients with internal disorders may have a lower increase in Hb level after PRBC transfusion 3.