Storage of Blood
Citrate phosphate dextrose adenine (CPDA-1) is an anticoagulant
preservative in which blood is stored at 1°C to 6°C. Citrate is an anticoagulant,
phosphate serves as a buffer, and dextrose is a red cell energy source. The addition
of adenine to CPD solution allows RBCs to resynthesize adenosine triphosphate (ATP),
which extends the storage time from 21 to 35 days. As a result, RBCs or whole blood
can be stored for 35 days when stored in CPDA-1.[46]
The shelf life can be extended to 42 days when AS-1 (Adsol), AS-3 (Nutricel), or
AS-5 (Optisol) is used.[47]
[48]
Adsol contains adenine, glucose, mannitol, and sodium chloride; Nutricel contains
glucose, adenine, citrate, phosphate, and sodium chloride. Optisol only contains
dextrose, adenine, sodium chloride, and mannitol. On a local level, 90% of our RBCs
are mostly stored in AS-1 at the University of California, San Francisco. On a national
level, 85% of the RBCs are collected in AS-1. The hematocrit of packed red cells
stored in AS-1 is approximately 60%. This duration of storage has been set by U.S.
federal regulation and is determined by the requirement that at least 70% of the
transfused RBCs remain in circulation for 24 hours after infusion. RBCs that survive
24 hours after transfusion disappear from the circulation at a normal rate. Those
that do not survive are subsequently removed from the circulation by the blood recipient.
That blood can be stored for 42 days is a mixed blessing. The
obvious advantage is the increased availability of blood. However, there are increasing
numbers of articles whose authors believe that blood stored for long periods is less
effective than fresher blood in critically ill patients, probably because of a leftward
shift in the oxygen-dissociation curve (see "Changes in Oxygen Transport").[16]
An increased incidence of postoperative pneumonia in cardiac patients has been associated
with the use of older blood.[15]
The citrate ion prevents clotting by binding calcium; dextrose
allows the RBCs to continue glycolysis and maintain sufficient concentrations of
high-energy nucleotides (ATP) to ensure continued RBC metabolism and subsequent viability
during storage. The storage at 1°C to 6°C assists preservation by slowing
the rate of glycolysis approximately 40 times the rate at body temperature. The
addition of adenine prolongs storage time by increasing RBC survival by allowing
RBCs to resynthesize the ATP needed to fuel metabolic reactions. Without adenine,
RBCs gradually lose their ATP and their ability to survive after transfusion.
During storage of whole blood and PRBCs, a series of biochemical
reactions occur that alter the biochemical makeup of blood and account for some of
the complications that are discussed later. During storage, RBCs metabolize glucose
to lactate, hydrogen ions accumulate, and
*Percent
recovery of OR
-tagged red blood cells at 24 hours.
plasma pH decreases. The storage temperatures of 1°C to 6°C stimulate the
sodium-potassium pump, and RBCs lose potassium and gain sodium. The osmotic fragility
of RBCs increases during storage, and some cells undergo lysis, resulting in elevated
plasma hemoglobin levels. Storage is associated with progressive decreases in RBC
concentrations of ATP and 2,3-diphosphoglycerate (2,3-DPG).
Packed RBCs have a slightly lower survival than whole blood ( Table
47-4
), although values for hemoglobin and potassium concentrations may
appear somewhat high in 35-day stored RBC concentrates. However, it should be remembered
that the total plasma volume in the concentrates is only 70 mL.
Frozen Storage
Satisfactory storage of RBCs in the frozen state became possible
when these cells, mixed with glycerol, could be frozen and thawed without damage.
RBCs previously frozen to 79°C in glycerol survive well in humans. RBCs must
be free from glycerol before being transfused; unfortunately, a simple and inexpensive
method of removing the glycerol has been difficult to develop. Valeri[49]
studied the efficacy of using frozen RBCs and has attempted to simplify the method
of freezing and thawing RBCs to make it a more viable process.
There are several advantages for frozen and thawed RBCs. Blood
of rare types can be stored for long periods, increasing viability and eliminating
outdating. Frozen, reconstituted blood is believed to be safer in patients who are
especially susceptible to allergic reactions, because the freezing and washing process
reduces sites with histocompatible antigens. Frozen, washed blood may reduce risk
of transfusion hepatitis. Frozen blood, low in fibrin and leukocytic aggregates,
would be safer in patients requiring massive blood transfusion, and frozen RBCs may
be desirable in clinical conditions requiring prompt tissue oxygenation because normal
levels of 2,3-DPG are retained in frozen erythrocytes. The efficacy of using frozen,
thawed RBCs on a large-scale basis was proved possible at Cook County Hospital in
Chicago, during a 28-month period.[50]
Despite
the advantages of frozen blood, its use has been limited and unlikely to be used
in the future to any extent.
