Stored blood for transfusions may have shorter shelf life than once thought
A new study suggests blood blanks may be carrying expired stock.
Researchers at Johns Hopkins University analyzed red blood cells in patients who were set to receive transfusions, and found blood older than three weeks may lack the flexibility required to deliver oxygen throughout the body.
"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," lead researcher Dr. Steven M. Frank, an associate professor of anesthesiology and critical care medicine at the Johns Hopkins University School of Medicine in Baltimore, said in a press release. "If I were having surgery tomorrow, I'd want the freshest blood they could find."
Frank's team enlisted 16 patients who were about to undergo spinal fusion surgery, a type of procedure in which doctors cut into the spine and join together vertebrae. Blood transfusions are often required. Six patients received five or more units of blood, while 10 needed three or fewer units, and each blood bag was analyzed for the red blood cells' "flexibility." Red cells in stored blood gradually over time lose flexibility or the ability that's required to push the cells through the smallest capillaries to delivery oxygen, according to the researchers.
The researchers found blood older than three weeks was more likely to have fewer flexible red blood cell membranes. After testing the blood cells once they were transfused into patients, they found the damage was irreversible and remained throughout the blood cell's life cycle, which is up to 120 days.
The study was published March 4 in Anesthesia & Analgesia.
Frank thinks blood banks may want to reconsider the current practice of transfusing blood stored up to six weeks, and dispensing the oldest blood first before it exceeds its shelf life.
"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," he said.
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According to the authors, an earlier 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.
However, Frank acknowledged in the study that blood banks do not have enough fresh blood for everybody, and that shorter storage periods would take away from inventory. But he notes one reason for the lack of availability of fresher bloods for adults is the routine practice of giving pediatric patients priority for the freshest units.
Sheila MacLennan, consultant hematology at NHS Blood and Transplant in the U.K. who was not involved in the research, told The Telegraph that storing blood for a shorter period could lead to more waste of a "very precious resource."
"There is no definitive evidence at present that transfusing 'older' blood is significantly worse for patients," she said.
"We're always concerned about the age of blood, but we're not going to get concerned about this extraordinarily until we see the results of the big clinical trials going on right now," Dr. Dana Devine, vice-president, medical, scientific and research affairs at Canadian Blood Services who was not involved in the research, told the Toronto Star.
More than 44,000 blood donations are needed every day, according to the American Red Cross, for a total of 30 million blood components are transfused each year.
