In a report published online in the journal Anesthesia & Analgesia, the Johns Hopkins investigators say red cells in blood stored for six weeks slowly lose the flexibility required to squeeze through the body's smallest capillaries to deliver oxygen. And unfortunately, the damage is irreversible.
"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."
This is bad news since there is already a shortage of blood available and if the available blood is considered "not usable", it will compound the problem further. Yet Frank says that storing blood beyond six weeks may need to be reconsidered.
In this research, Frank and his colleagues studied 16 patients who were 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 research team sampled each of the 53 bags of blood used and measured the flexibility of the red blood cells. The results indicated that blood older than three 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.
The team also took blood samples from patients in the three days following surgery. Even though the blood were now back in the regular body with proper pH [acidity], electrolytes and oxygen levels, the damage to the red cells was not reversible and seemed to be permanent. The damaged blood cells would most probably remain dysfunctional for their full life cycle of 120 days.
According to the research report, the average age of the blood given in the study was more than three weeks. Only three samples in the study were two weeks old or less.
This research indicates that the policy of how long to store blood may need to be reviewed.
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