(5) The auxiliary preservative solutions in the additive systems are not
approved for whole blood, plasma components, platelets, or for use in plasma-pheresis
procedures. The anticoagulant CP2D has been approved for the preparation of routine
blood components including single donor plasma, cryo-precipitated antihemophilic
factor, and platelet concentrate.
(6) Certain measurable biochemical changes occur when blood is stored at
1C to 6C. These changes, some of which are reversible, are known as the "storage
lesion" of blood. These changes are tabulated for CPD and CPDA-1 stored blood in
table 1-2 and additive systems in Table 1-3. Except for oxygen-transporting discussed
below, these rarely have clinical significance because transfusion volumes are small
and the recipient's compensatory homeostatic mechanisms reverse these changes.
Even in massive transfusion, the adverse effects of the red cell storage lesion are
usually inconsequential unless the recipient is already severely compromised.
(7) In red cell storage and preservation, it is important to maintain oxygen-
carrying and oxygen-releasing capacities of hemoglobin. The concentration of red cell
2,3-DPG influences the release of oxygen to the tissues. If 2,3-DPG levels are high,
more oxygen is released at a given PO2. Lower red cell levels of 2,3-DPG cause greater
affinity of hemoglobin for oxygen so that less oxygen is released at the same PO2.
(8) Concentrations of 2,3-DPG are affected by pH. The initial pH of blood
collected in CPD and measured at the temperature of storage is approximately 7.4 to
7.5. As stored red blood cells metabolize glucose to lactate, hydrogen ions accumulate,
plasma pH falls, and 2,3-DPG declines. Table 1-2 tabulates these changes for CPD and
CPDA-1. During the second week of storage, the pH of CPD stored blood falls below
7.0. As pH drops, there is a fall in red cell 2,3-DPG. Concentrations of 2,3-DPG are
normal in CPD-stored blood for about 10 days. When blood is stored in CPDA-1, 2, 3-
DPG levels initially fall slightly more rapidly than in CPD, but near normal levels are
maintained for 12 to 14 days.
(9) Following transfusion, stored red blood cells regenerate ATP and 2,3-
DPG, resuming normal energy metabolism and hemoglobin function as they circulate in
the recipient. It usually takes from 3 to 8 hours for severely depleted cells to regenerate
half of their 2,3-DPG levels and approximately 24 hours for complete restoration of 2,3-
DPG and normal hemoglobin function. In red cell storage, maintaining cell viability is
unclear. On theoretical grounds, recipients likely to be most affected by low 2,3-DPG
levels in transfused blood are those receiving massive quantities of stored blood in a
short time, and those particularly vulnerable to the effects of tissue hypoxia; examples
include newborns undergoing exchange transfusion, patients with small blood volume
who receive large volumes of blood, and patients undergoing coronary artery bypass
surgery. Such patients usually receive blood less than 7 to 10 days old.