Today we’ll be discussing transfusion of fresher versus older red blood cells. Over time, red cells develop altered structural and biochemical storage lesions. A variety of additive solutions, anticoagulation solutions, storage bags, and processing procedures affect red cell storage. FDA guidelines permit red cells to be stored for 42 days, but most units are transfused within three weeks.
Dr. James Zimring describes the FDA guidelines:
“The traditional measures for licensing criteria are less than 1% hemolysis in the bag and an average post-transfusion survival of 75% 24-hours after transfusion, and those are very meaningful measures because it’s a fair statement that red cells that don’t circulate can’t carry oxygen.”
Whether red cell storage lesions affect oxygen delivery or matter clinically, has been a heavily debated and studied topic. Retrospective studies have produced conflicting conclusions. Within the last three years, however, three larger randomized controlled trials, or RCTs, found that younger red blood cells are not associated with better clinical outcomes. The Age of Red Blood Cells in Premature Infants (or ARIPI) study examined 377 very low birth weight babies and detected no difference in fresher versus standard-issue red cells. The Red Cell Storage Duration Study (or RECESS) reported similar results in 1,418 cardiac surgery patients, and the Age of Blood Trial (or ABLE) examined over 2,400 intensive care patients transfused with either red cells stored less than 8 days or standard issue cells.
Dr. Zimring comments:
“The randomized controlled trials have been run and the fact that they have not observed any differences is a very comforting observation in the context of standard practice, but there are additional concerns that the RCTs may not cover. All RCTs are limited in their statistical power so that’s always a concern. In addition, these RCTs only studied particular clinical situations.”
Other clinical situations such as trauma patients and septic patients may encompass special situations which require further study. In addition, none of the RCTs have evaluated the oldest red cells at the 42-day storage limit.
The evidence is reassuring that standard-issue red cells are not clinically superior to fresher units, but further research is needed. Furthermore, new measures of red cell storage lesions, many of which are based on large platforms of metabolic or proteomic data, may provide new insight for the study of red blood cell storage.
We’ll be back with another edition of Transfusion News on May 15th. Thanks for joining us.
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