March 19, 2008 -- Heart surgery patients who get transfusions with blood stored for longer than two weeks have a higher risk of complications and death than patients who get newer blood, a new study finds.
The risk of death following heart surgery was 30% higher among patients transfused with blood stored for longer than 14 days, researchers from the Cleveland Clinic reported.
These patients were also more likely to suffer surgical complications, including longer airway intubation, kidney failure, and infection.
The study, which appears in tomorrow's New England Journal of Medicine, is not the first to suggest a link between stored blood age and surgical outcomes. But it is among the largest and most rigorously designed investigations ever to address the question.
"We know that from the time blood is donated changes start occurring," Cleveland Clinic anesthesiologist and study researcher Colleen Gorman Koch, MD, tells WebMD.
New Blood, Old Blood
More than 14 million units of blood are transfused each year in the United States, according to government figures.
Transfusions save lives, but there is also extensive evidence linking them to an increased risk for complications and death in critically ill patients.
Studies examining the impact of blood age on surgical outcomes have been more equivocal, with some finding older blood to be associated with poorer outcomes and others finding no link.
The FDA allows red blood cells to be stored for up to 42 days. The average time of storage is estimated to be 15 days in a 2005 government survey.
In an effort to shed light on the issue, Koch and colleagues reviewed outcomes among 6,002 patients who had coronary artery bypass surgery, heart-valve surgery, or both at the Cleveland Clinic between the summer of 1998 and January 2006.
About half of the patients had transfusions from blood that had been stored for 14 days or less, and half had transfusion from blood stored longer. The average length of storage was 11 days in the "new blood" group and 20 days in the "older blood" group.
After controlling for a long list of factors that could affect outcomes and survival, the researchers reported statistically significant increases in death and complications among the patients treated with the older blood.
These patients had higher rates of death prior to leaving the hospital following surgery (2.8% vs. 1.7%), intubation lasting more than 72 hours (9.7% vs. 5.6%), kidney failure (2.7% vs. 1.6%), and potentially life-threatening blood infections (4% vs. 2.8%).
The death rate a year after surgery among patients infused with older blood was also significantly higher (11% vs. 7.4%).
Is That Transfusion Needed?
Koch says the research linking transfusions to poorer outcomes should make cardiac surgeons stop and think before they give patients transfusions they may not need.
"Most [cardiac surgery] transfusions involve one to two units," she says. "A one-unit transfusion isn't done because a patient is bleeding to death."
But she adds that it is too soon to call for policy changes shortening the time that stored blood can be kept.
The researchers will conduct a randomized, controlled trial that may provide definitive answers within two-and-a-half years, she says.
In an editorial published with the study, John W. Anderson, MD, of the VA San Diego Healthcare System, wrote that the findings should "arm those who believe that the transfusion of older red-cell units carries risk and should be avoided."
But he added that the study will not end the debate, because it included a relatively homogeneous group of patients.
"The study simply adds an important piece to the discussion of the risks of transfusion but does not settle the issue of best practices," he writes.