Older Blood Boosts Chances of Infection in Transfusion Patients

TUESDAY, Oct. 28, 2008 (HealthDay News) -- Hospital patients who receive a transfusion of stored blood that is 29 days or older face double the risk for developing one or more serious infections compared to those who get "fresher" blood, new research indicates.

The study authors pointed out that current U.S. regulations set the upper limit for blood storage at 42 days, at which point the blood must be thrown away. Yet, the latest finding suggests that infection risk might actually begin nearly two weeks before that accepted cut-off date.

"This issue is something that has been on the radar for some time, so the idea that aging blood can pose problems is not completely new," said study author Dr. Raquel Nahra, who conducted her research while at Cooper University Hospital in Camden, N.J. "But the bottom line here is that what we found is that patients who received blood transfusions with blood 29 days or older appeared to have a greater risk for infection."

Nahra is currently working at Stark Medical Center in Fort Smith, Ark. She and her colleagues were scheduled to present their findings Tuesday at the American College of Chest Physicians annual meeting, in Philadelphia.

The observations follow a 2006 finding from Duke University Medical Center researchers that seriously ill heart patients who received a transfusion of older blood -- between 31 to 42 days old -- faced a higher risk of death than similar patients who got "fresher" blood (stored for up to 19 days).

The new research team noted that the existing threshold was established to deal with the fact that while in storage red blood cells release cytokines, which are known to dampen a transfusion patient's immune system -- rendering the patient more susceptible to infection.

Cytokine release tends to begin around two weeks into blood storage, mounting to maximum levels even after the 42-day line in the sand.

To get a handle on possible links between blood age and infection risk among transfusion patients, Nahra and her colleagues analyzed records concerning 422 transfusion patients -- average age 66 -- who had been admitted to a single hospital intensive care unit between 2003 and 2006.

On average, the blood on hand at the ICU was 26 days old, while 70 percent of all the available blood was more than 21 days old.

Nahra and her team tracked the age of the first unit of blood each patient received, as well as the age of the oldest unit of blood they received.

The research team found that, following transfusion, 11 percent of the patients died, while 57 patients went on to develop one or more serious infections, including pneumonia, upper respiratory infection, sepsis and/or shock.

Specifically, 32 patients developed a single infection, 21 developed two such infections, and four patients developed three infections.

Patients who received blood transfusions with units of blood that had been packed for 29 days or longer were found to be twice as likely to develop such an infection as those getting blood stored for 28 days or less.

The age of the oldest unit of blood used during any transfusion was the factor most strongly linked to infection risk -- although the age of the first unit of blood used was also associated with an increased risk, the study found.

Despite the apparent infection association, no link was found between receiving a transfusion of older blood and a greater risk for death.

Noting that hospitals often use the oldest blood on hand first to minimize waste, Nahra and her team concluded that more studies are needed to identify the ideal storage period for blood, to protect against infection risk.

She noted that, as a practical matter, hospital patients cannot routinely request "fresher blood."

"It is too early to conclude that patients should be worried," she said, "but I would say that they should be aware that this is a possible complication, and future studies should explore that question."

Dr. Richard J. Benjamin, chief medical officer for the American Red Cross, described the study as both "interesting and provocative," but he stressed the need for further research.

"It would be premature to base changes in medical practice on the data this study provides," he said, noting it can be difficult to draw definitive conclusions based on research that looks back on patient experience without controlling for all the various factors that might color the findings.

For example, "the sicker patients received more blood than the less sick patients, and were therefore more likely to receive at least one older unit," he pointed out. "[So] it is not possible to discern whether the worse clinical condition caused more old blood to be transfused, or if the patients were sicker because they received more old blood."

Noting that research is under way to try to answer such questions, Benjamin emphasized that "the judicious use of blood transfusion is lifesaving and allows the performance of medical and surgical procedures that would not otherwise be possible due to blood loss. Physicians and patients need to weigh the potential benefits against the small risk of harm caused by transfusions."

More information

For more on blood safety, visit the U.S. Food and Drug Administration.