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.
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| Contact: Stephanie Desmon sdesmon1@jhmi.edu 410-955-8665 Johns Hopkins Medicine Source:Eurekalert |