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Storing Blood Before Transfusion

Past studies into how long red blood cells can be safely stored before transfusion have had differing results.Jochen Sands/Digital Vision/Thinkstock

Red blood cells transport oxygen throughout the body. During major surgeries, patients often need transfusions of red blood cells to replace lost blood. In the United States, the cells may be stored for up to 42 days — although the average age at the time of transfusion is currently 18 days. Red blood cells go through many changes while in storage that may decrease their ability to carry oxygen. It remains unclear whether these changes affect the health of patients given transfusions. This question is especially important for cardiac surgery patients because their hearts may be temporarily weakened by their procedures.

The researchers randomly split more than 1,000 complex cardiac surgery patients with an average age of 71 years into 2 groups. The short-term storage group received transfusions of red blood cells that had been stored for 10 days or less. The long-term storage group received cells stored for 21 days or more based on the standard of care, which is to transfuse the oldest stored blood units first in order to use them before their expiration dates.

To track changes in patient health, the researchers used a measure called MODS (Multiple Organ Dysfunction Score). This scores the health of 6 different organ systems: lung, kidney, liver, cardiovascular (heart and blood vessels), blood, and neurologic (brain and nerves). The results were published on April 9, 2015, in the New England Journal of Medicine.

The average change in MODS score from before surgery to 7 days or 28 days post-surgery did not differ between the 2 groups. There also were no differences in the frequency of post-surgery complications and deaths. This suggests that changing standard practice to transfusing only red blood cells stored for short periods would not benefit patients undergoing complex cardiac surgery.

The study did find that the long-term storage group experienced more complications related to liver function, leading to a larger change in that component of the MODS score. However, this was due to increased levels of bilirubin, a substance created when the liver breaks down red blood cells. The result wasn’t surprising, because longer storage durations can make some red blood cells more fragile, causing them to break down more easily. This elevated bilirubin didn’t harm patients’ clinical outcomes.

“These findings are reassuring because they do not support the need to modify transfusion practices in adult patients undergoing complex cardiac surgery,” says Dr. Keith Hoots of NHLBI. “In particular, there does not appear to be something gained by only transfusing red blood products stored for 10 days or less.”

Most of the blood transfused during the study had been stored for less than 35 days, so it’s still unknown whether blood stored for 35–42 days would be equally safe to use in these patients. Future studies will also need to examine whether red-cell storage duration affects the health of patients who need transfusions for other reasons.