A Cleveland Clinic study said found that heart surgery patients who received transfusions with blood that has been stored more than 14 days were more likely to suffer from kidney failure, sepsis, prolonged intubation and in-hospital death.

Dr. Colleen Gorman Koch, the study's lead author, said as many as half of all heart surgery patients receive blood transfusions.

More than 14 million units of blood are transfused in the United States each year and the median duration of blood storage is 15 days. The U.S. Food and Drug Administration allows for blood to be stored up to 42 days before it must be discarded, the Cleveland Clinic said in a release.

The study was published in the March 20 issue of the New England Journal of Medicine.