c. Effects of Red Blood Cell Transfusion.
(1) Circulation. When a unit of WB is transfused rapidly (30 to 60 minutes)
to a patient with a normal blood volume, the blood volume is increased by this amount.
After approximately 24 hours, the blood volume has returned to its pretransfusion level.
If plasma alone is transfused, the blood volume may readjust more rapidly. Some
patients, such as those with chronic renal disease, may require prolonged periods to
readjust their blood volume.
(2) Hemoglobin. The effects of red blood transfusion on the recipient's
hemoglobin and hematocrit will be affected by the recipient's blood volume,
pretransfusion hemoglobin and hematocrit, the clinical condition of the patient (stable,
bleeding, etc), and the hemoglobin and hemacrit of the donor unit. For instance, a
hypothetical patient with a blood volume of 5,000 ml and hemoglobin of 8 gm/dl has a
total hemoglobin of 400 gm. If the patient is transfused with one unit of WB, the blood
volume becomes 5,517 ml and the total hemoglobin 460 gm, which results in a
hemoglobin concentration of 8.4 gm/dl. If red blood ceils are transfused, the blood
volume is 5,300, the total hemoglobin 460 gm, and the hemoglobin concentration 8.7
gm/dl. If the patient is able to readjust the blood volume to baseline levels within 24
hours, the result will be 5,000 ml blood volume, 460 gm hemoglobin, and a hemoglobin
concentration of 9.2 gm/dl with either WB or RBCs.
(3) Red blood cell production. Transfusion of red cells may result in a
decrease in the recipient's own RBCl production because of a suppression of
erythropoietin. Thus, many patients with a stable chronic anemia may receive little
benefit from RBC transfusion since their hemoglobin rapidly fails to pretransfusion levels
because of diminished production of their own RBCs.
d. Survival of Transfused Red Blood Cells. The normal red cell has a life
span of approximately 120 days. Each unit of blood contains RBCs of all ages between
1 and 120 days. As the unit of blood is stored, the RBCs continue to age and these
senescent RBCs are removed from the circulation within 24 hours, after transfusion.
Thus, when stored blood is transfused, there is a slight decrease in the proportion of
RBCs surviving 24 hours after transfusion. Approximately 70 percent to 80 percent of.
stored in CPD for 21 days, or CPDA-1 for 35 days, survive following transfusion. The
remaining RBCs survive normally, and they are destroyed linearly with a mean half-life
of 50 to 60 days. The survival of transfused RBCs is affected by the recipient's health,
and may be decreased in patients with active bleeding (and iatrogenic blood loss),
hemolytic anemia resulting from defects extrinsic to the RBC (autoantibodies,
alloantibodies, and hypersplenism), and chronic renal or Iiver failure.