NEJM: Older stored blood poses postoperative risk
Researchers at the Cleveland Clinic Foundation found that the transfusion of blood that had been stored for more than two weeks significantly increased the risk of complications as well as reduced short-term and long-term survival in patients undergoing cardiac surgery.

Colleen Gorman Koch, MD, and colleagues reported in the March 20 issue of the New England Journal of Medicine that stored red cells undergo progressive structural and functional changes over time.

U.S. Regulations allow blood to be stored for as long as six weeks, which allows time to ship it across the country and provides a cushion against shortages. Most blood banks operate on a first in, first out basis, so that patients typically receive the oldest blood available. The median storage time of transfused blood is 15 days, according to the Los Angeles Times.

The investigators examined data from a total of 2,872 patients given red-cell transfusions during coronary-artery bypass grafting, heart-valve surgery, or both between June 30, 1998, and Jan. 30, 2006. The patients received 8,802 units of blood that had been stored for 14 days or less (newer blood), and 3,130 patients received 10,782 units of blood that had been stored for more than 14 days (older blood), according to the researchers.

Koch and colleagues found that the median duration of storage was 11 days for newer blood and 20 days for older blood.

The patients who were given older units had higher rates of in-hospital mortality (2.8 percent vs. 1.7 percent), intubation beyond 72 hours (9.7 percent vs. 5.6 percent), renal failure (2.7 percent vs. 1.6 percent) and sepsis or septicemia (4 percent vs. 2.8 percent), the authors wrote.

The researchers also found that a composite of complications was more common in patients given older blood (25.9 percent vs. 22.4 percent). Similarly, older blood was associated with an increase in the risk-adjusted rate of the composite outcome.

Koch and colleagues found that at one year, mortality was significantly less in patients given newer blood (7.4 percent vs. 11 percent).

The Cleveland Clinic researchers are also planning to conduct a prospective, blinded, randomized controlled study to confirm the findings.