The storage of red blood cells (RBC) in the blood bank leads to a progressively lower oxygen carrying capacity over time. Once these RBC are transfused to a patient, how long does it take before normal oxygen carrying capacity is restored?
A. < 6 hours after transfusion
B. > 6 hours but < 12 hours after transfusion
C. > 12 hours but < 24 hours after transfusion
D. > 24 hours but < 48 hours after transfusion
E. > 48 hours after transfusion
The correct answer is D. There are several things that occur with ex vivo storage of RBC's - collectively referred to as the "storage lesion." First, ATP is depleted and membrane lipids and cytoskeletal elements are damaged (oxidant injury) - this leads to decreased deformability of the red cell in the microcirculation (it gets "clogged up" in the capillaries). Second, the levels of 2,3-DPG are essentially depleted to zero after a week of storage. Fortunately, 2,3-DPG levels return to normal within 24 hours or so following transfusion. Hence, normal oxygen carrying capacity is back to normal somewhere between 24-48 hours after transfusion. Until that time, RBC are essentially a good volume expander, but you may not necessarily get all the oxygen delivery benefits!