A new study showed that blood deteriorates with age and heart surgery patients are more likely to suffer problems if they receive transfusions of blood that has been stored for more than two weeks than those who get fresher blood, said a study in Thursday's New England Journal of Medicine.

In the study, researchers examined the records of 6,000 patients treated at the Cleveland Clinic, who were given blood transfusions during heart-bypass or heart-valve surgery.

A little less than half of the patients received blood that had been stored for 14 days or less, and a little more than half got blood that was older.

The study found that the one-year survival rate was 89 percent for those who got older blood, but nearly 93 percent for patients who got fresher blood.

Complication rates were higher in the older blood group, with higher proportions of those patients suffering kidney failure, blood infections or multiple organ failure.

The findings aren't expected to prompt immediate changes in procedures at blood banks as the issue needs to be be studied more rigorously.

The Food and Drug Administration allows blood to be stored for as long as 42 days. The median storage time of red blood cells nationally is 15 days, which means about half of the country's supply falls into the older range of stored blood.

The study's lead author, Dr. Colleen Gorman Koch of the Cleveland Clinic, did not call for an immediate change to the FDA rule, but said a more rigorous study is already under way that could carry the scientific weight to persuade the FDA to reconsider its policy.

The study findings should urge doctors to be "more conservative with how they approach blood transfusion," says Koch.

Researchers aren't sure why older blood may be bad for patients, but they do know that the red cells undergo physical and chemical changes during storage that may affect their function and viability after surgery.

(Agencies via Xinhua News Agency March 20, 2008)