From the Research
The expected decrease in hemoglobin (Hb) when comparing a hematocrit (Hct) of 0.23 to 0.31 is approximately 2.7 g/dL. This calculation is based on the established relationship between hemoglobin and hematocrit, where hemoglobin (g/dL) is approximately one-third of the hematocrit when expressed as a percentage. Using this formula, a hematocrit of 0.31 (or 31%) corresponds to a hemoglobin of about 10.3 g/dL, while a hematocrit of 0.23 (or 23%) corresponds to a hemoglobin of about 7.6 g/dL. The difference between these two hemoglobin values (10.3 - 7.6) gives us the expected decrease of 2.7 g/dL. This relationship exists because hematocrit represents the volume percentage of red blood cells in blood, while hemoglobin is the oxygen-carrying protein contained within these cells. The 3:1 ratio between hematocrit and hemoglobin is maintained in most clinical scenarios, though it can vary slightly in certain pathological conditions such as hemoglobinopathies or significant changes in plasma volume 1. Key points to consider include:
- The optimal hematocrit value lies between the extreme cases of pure blood plasma and 100% hematocrit, with a trade-off between oxygen binding and blood viscosity 1.
- Erythropoiesis-stimulating agents (ESAs) are commonly used to treat anaemia in people with chronic kidney disease (CKD), but their use has been associated with cardiovascular events 2.
- Iron deficiency syndromes, including absolute iron deficiency, functional iron deficiency, and iron sequestration, can impact erythropoiesis and anemia management 3.
- ESAs as replacement therapy for blood transfusions in critically ill patients with anaemia may result in a small reduction in the proportion of patients who receive RBC transfusions, but the clinical relevance is questionable 4. However, the most recent and highest quality study 1 supports the established relationship between hemoglobin and hematocrit.