A small study from Johns Hopkins adds to the growing
body of evidence that red blood cells stored longer
than three weeks begin to lose the capacity to
deliver oxygen-rich cells where they may be most
needed.
In a report published online in the journal
Anesthesia & Analgesia, the Johns Hopkins
investigators say red cells in blood stored that
long gradually lose the flexibility required to
squeeze through the body’s smallest capillaries to
deliver oxygen to tissue. Moreover, they say, that
capacity is not regained after transfusion into
patients during or after surgery.
"There's more and more information telling us that
the shelf life of blood may not be six weeks, which
is what the blood banks consider standard," says
study leader Steven M. Frank, M.D., an associate
professor of anesthesiology and critical care
medicine at the Johns Hopkins University School of
Medicine. "If I were having surgery tomorrow, I'd
want the freshest blood they could find."
Frank acknowledges that blood banks do not have
enough fresh blood for everybody, and that shorter
storage periods would result in diminished inventory.
But he says that the current practice of transfusing
blood stored up to six weeks may need to be
reconsidered.
One previous, large study published in the New
England Journal of Medicine has already shown that
cardiac surgery patients who received blood stored
longer than three weeks were almost twice as likely
to die as patients who got blood that had been
stored for just 10 days.
For the new study, Frank and his colleagues enrolled
16 patients scheduled to have spinal fusion surgery,
a type of operation that typically requires blood
transfusions.
Six of the patients received five or more units of
blood, while 10 needed three or fewer units. The
researchers drew samples from every bag of blood
used -- 53 in total -- and measured the flexibility
of the red blood cells. What they found is that
blood older than 3 weeks was more likely to have
less flexible red blood cell membranes, a condition
that may make it more difficult for blood to deliver
oxygen, Frank says.
The team also took blood samples from patients in
the three days following surgery. Even though the
blood cells were out of storage and back in
biological environments with proper pH (acidity),
electrolytes and oxygen levels, the injury to the
red cells was not reversible and appeared to be
permanent. The damaged blood cells would likely
remain dysfunctional for their life cycle limit,
which is up to 120 days, Frank says.
Frank also noted that patients in the study who got
fewer units of blood had healthier red cells overall,
even though the blood was just as old and showed
cell damage. He says it is likely that a small
amount of these problem cells make less of a
difference than when a large number of damaged cells
are present.
According to the research report, the average age of
the blood given in the study was more than 3 weeks.
Only three samples in the study were 2 weeks old or
less. One reason for the lack of availability of
fresher bloods for adults, Frank says, is the
routine practice of giving pediatric patients
priority for the freshest units.
In fact, he notes, blood banks dispense the oldest
blood first so that it doesn’t exceed its shelf life
before it can be used. "As a colleague said, it’s
like how they sell milk in the grocery store -- they
put the oldest cartons out front so they can sell
them before they expire," Frank says.
Two large randomized controlled studies, one at many
centers across the United States, including Johns
Hopkins, and one in Canada, are under way to
determine the relative safety of older versus newer
blood, and the results are expected next year. Frank
says blood banks need to be prepared to change
practice if those studies show that a six-week shelf
life for blood is just too long.
The study was supported in part by the National
Institutes of Health’s National Institute on Aging
(R01 AG021523) and National Heart, Lung, and Blood
Institute (R01 HL092259-01).
Other Johns Hopkins researchers involved in the
study include Bagrat Abazyan, M.D.; Masahiro Ono,
M.D.; Charles W. Hogue, M.D.; David B. Cohen, M.D.,
M.P.H.; Daniel E. Berkowitz, M.D.; Paul M. Ness,
M.D.; and Viachaslau M. Barodka, M.D.
Ness has consulted for Terumo BCT and Fenwal Labs,
both companies involved with blood storage. Nothing
in this study directly benefits these companies. The
terms of these arrangements are being managed by The
Johns Hopkins University in accordance with its
conflict of interest policies.
for more information
http://www.hopkinsmedicine.org/
(MDN)
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