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NHLBI funds research to improve safety of red blood cell transfusions
Jun 21, 2010 - 3:59:36 AM

The National Heart, Lung, and Blood Institute (NHLBI), part of the National Institutes of Health, is funding nine research grants to determine if the safety and efficacy of red blood cell transfusions vary depending on how long the cells have been stored. One of the grants supports the first large, multi-center, randomized clinical trial to compare outcomes in heart surgery patients who receive transfusions of red blood cells that have been stored for shorter or longer amounts of time. The other eight research grants provide about $3.9 million per year over four years to assess the safety and efficacy of red blood cell transfusions.

These are the first research projects to systematically examine the storage- and preparation-dependent changes that red blood cell units undergo, said NHLBI Acting Director Susan B. Shurin, M.D. These basic and translational studies embody the NHLBI's goal to advance the science of blood safety in the nation. What we learn will help guide clinical practice.

U.S. medical workers administer about 14.7 million bags of blood to about five million patients each year. These transfusions contain red blood cells to treat patients with anemia or to replenish blood lost to surgery or severe injury.

While transfusions unquestionably save the lives of many patients, they can cause complications. Some studies suggest that the way donated blood is processed and the amount of time it is stored play a role in the changes that occur.

Currently, FDA regulations allow facilities to store red blood cells for up to 42 days at about 4 degrees Celsius (39 degrees Fahrenheit) before being transfused. The average age of transfused red blood cells in the United States is estimated to be a little more than 16 days.

Studies have shown that blood processing and storage cause several changes in red blood cell units, including lower concentrations of molecules that regulate how oxygen is delivered to patients' tissues. Storage and preparation also affect the deformability of red blood cells. Deformability normally allows the cells to squeeze through capillaries half their size.

Scientists do not fully understand the causes, extent, and timing of these changes, or if they affect transfused patients' health. Recent research on patient outcomes has yielded conflicting results. For example, some studies suggest that red blood cells stored for longer periods of time are less effective and more likely to harm transfusion recipients. They associate older stored red cells with more complications and deaths among heart surgery patients, trauma patients, and critically ill patients in the intensive care unit. In contrast, other investigations have found no differences in clinical outcomes using red cells stored short-term or long-term.

Most of these studies, however, were observational and cannot prove cause and effect. In addition, these studies might be difficult to interpret accurately because they cannot be adjusted to rule out potential confounding effects such as patients' illnesses, because they involved small sample sizes, or because other factors prevent the results from being applied to broader groups.

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