Why is the hemoglobin normal right after a big blood loss?
Q. Immediately after an acute episode of blood loss – following a motor vehicle accident, for example – the hemoglobin level is normal. Why is that? Are the other red cell indices normal too?
A. Immediately after acute blood loss, all the laboratory red cell indices are normal! The hemoglobin, RDW, RBC, MCH, and the MCHC are all normal. Because really, although the patient has lost blood (and therefore is in trouble because he/she has fewer red cells to transport oxygen through the body), the blood that’s examined in the laboratory appears totally normal! It has the same number of red cells per unit volume, and the red cells themselves are perfectly normal (assuming the patient’s blood was normal to begin with). This is because during acute blood loss, you’re losing red cells but also the plasma that goes along with them. So the blood remaining in the patient is totally normal – it’s just that there isn’t enough of it.
