The impact of red blood cell storage duration on tissue oxygenation in cardiac surgery

Objective

Although storage alters red blood cells, several recent, randomized trials found no differences in clinical outcomes between patients transfused with red blood cells stored for shorter versus longer periods of time. The objective of this study was to see whether storage impairs the in vivo ability of erythrocytes to traverse the microcirculation and deliver oxygen at the tissue level.

Methods

A subset of subjects from a clinical trial of cardiac surgery patients randomized to receive transfusions of red blood cells stored ≤10 days or ≥21 days were assessed for thenar eminence and cerebral tissue hemoglobin oxygen saturation (S_tO₂) via the use of near-infrared spectroscopy and sublingual microvascular blood flow via side-stream darkfield videomicroscopy.

Results

Among 55 subjects, there was little change in the primary endpoint (thenar eminence S_tO₂ from before to after transfusion of one unit) and the change was similar in the 2 groups: +1.7% (95% confidence interval, ?0.3, 3.8) for shorter-storage and +0.8% (95% confidence interval, ?1.1, 2.9) for longer-storage; P = .61). Similarly, no significant differences were observed for cerebral S_tO₂ or sublingual microvascular blood flow. These parameters also were not different from preoperatively to 1 day postoperatively, reflecting the absence of a cumulative effect of all red blood cell units transfused during this period.

Conclusions

There were no differences in thenar eminence or cerebral S_tO₂, or sublingual microcirculatory blood flow, in cardiac surgery patients transfused with red blood cells stored ≤10 days or ≥21 days. These results are consistent with the clinical outcomes in the parent study, which also did not differ, indicating that storage may not impair oxygen delivery by red blood cells in this setting.