Use of older blood also is associated with an increased risk for kidney problems, acute respiratory distress and longer confinement to intensive care units, the researchers from Duke University Medical Center and Columbia University found.

"We did find a significant association between older blood and adverse outcomes," said Elliott Bennett-Guerrero, M.D., a Duke anaesthesiologist who was the study's lead investigator. "Our results show that the number of transfusions given is a robust predictor of long-term mortality, and that the duration of storage also has independent adverse effects as well," he continued. "We believe our findings provide intriguing avenues for future study."

"Scientists have long known that red blood cells undergo significant changes during their storage, but little had been known about whether or not these changes have any clinical implications for patients," Bennett-Guerrero said. Previous studies of lower risk cardiac surgical patients found a link between age of transfused blood and adverse outcomes, but no risk of increased mortality, Bennett-Guerrero said.

For their study, the researchers retrospectively analysed the medical files of 321 patients who underwent a repeat open-heart procedure for coronary artery bypass or valve replacement between 1995 and 2001 and who received donated blood during surgery or recovery. For comparison purposes, the researchers assigned patients into four groups, based on the age of the oldest unit of blood they received: 1-19 days, 20-26 days, 27-30 days, 31-42 days.

The researchers found that increasing age of the blood corresponded significantly with an increased risk of death. "In terms of mortality, kidney damage and length of stay in the intensive care unit and hospital, we saw the rate of risk increase with each successive quartile," Bennett-Guerrero said.

MEDICA.de; Source: Duke University Medical Center