The duration of red blood cell storage did not adversely affect outcomes in ventilated patients receiving transfusions, according to a small randomized trial.
There was no difference in short-term pulmonary, immunologic, or coagulation status between 50 patients who received fresh red blood cells (median storage of four days) and 50 who received standard-issue red blood cells (median storage duration of 26.5 days), reported Daryl Kor, MD, from the Mayo Clinic in Rochester, Minn., and colleagues in the American Journal of Respiratory and Critical Care Medicine.
Specifically, there was no difference in the primary outcome of change in pulmonary gas exchange — assessed by the partial pressure of arterial oxygen to fraction of inspired oxygen concentration ratio — at 2.5 ± 49.3 for fresh cells versus -9.0 ± 69.8 for standard-issue cells (P=0.22).
The duration of red blood cell storage has been linked to an increased risk of transfusion-related pulmonary complications, Kor’s group wrote. Mechanistic data have outlined alterations in red blood cells during storage.
“These alterations have been purported to potentially influence the recipient’s respiratory and immunologic response to the transfused blood product,” they wrote.
To test this theory, the researchers conducted a double-blind clinical trial in which they enrolled 100 patients and randomized them to a single unit of either fresh red blood cells or standard-issue red blood cells. The majority of patients in the standard-issue group received a red blood cell unit that had been stored for more than 21 days.
Most of the patients received an ABO-and-Rh-identical red blood cell unit, while the reminder received an ABO-and-Rh-compatible unit. There was no difference in the proportion of patients who received nonidentical, ABO-compatible red blood cells (18% for fresh cohort versus 12% for standard issue cohort, P=0.40).
The mean standard deviation from the initiation of intervention red blood cell transfusion to the post-transfusion measurements was 1.8 ± 0.46 hours for the fresh blood cohort and 1.9 ± 0.63 hours for the standard-issue group (P=0.59).
In addition to the lack of difference in the primary outcome, there were no significant differences seen for immunologic status, including interleukin-8 and C-reactive protein, or coagulation status.
The authors noted that median tidal volumes following red blood cell transfusion were similar in the two groups: 7.7 ml/kg per predicted body weight (PBW) for the fresh cohort, versus 7.5 ml/kg per PBW for the standard-issue group (P=0.23).
Finally, there were no significant differences in intermediate outcomes, such as new or progressive transfusion-related acute lung injury (P=0.62) or organ failures (P=0.80). However, the authors cautioned that the study was not sufficiently powered to adequately evaluate these particular endpoints.
The study had other limitations: It was done at a single center, tertiary-care facility in a small patient population. Also, the follow-up period was short, so delayed responses to the transfused red blood cell units were not identified.
The investigators noted that their results differed from earlier study results that have found storage duration and adverse clinical outcomes; one possible reason is that patients in this study received a similar red blood cell dose, while earlier researchers did not adjust for dose, they suggested.
Also, pre-storage leukocyte reduction was used for all red blood cell units transfused — including fresh ones — in this study, and this has been shown to lessen the accumulation of bioactive substances, they explained.
The study offers proof that larger clinical trials randomizing patients to fresh red blood cell units or prolonged storage units are ethical and possible, the authors concluded.
The study was funded by grants from the National Institutes of Health and the department of critical care medicine at the Mayo Clinic College of Medicine. No author disclosures were provided.