• Stored blood may lose ability to deliver oxygen to tissues

WASHINGTON - Much of the stored blood given to millions of people every year may lack a component vital for it to deliver oxygen to the tissues. Nitric oxide, which helps keep blood vessels open, begins breaking down as soon as blood goes into storage, two research teams report in separate studies in this week's online edition of Proceedings of the National Academy of Sciences.

In recent years, doctors have become increasingly concerned about levels of heart attack and stroke in patients receiving transfusions and the new findings may help explain that.