Background/Case Studies: In North America, red cell concentrates (RCCs) are cryopreserved for long-term storage (~30 years) at temperatures below -65 °C using a high glycerol (40%) method. Occasionally during long-term storage these units may be unintentionally exposed to transient warming events (TWEs). Freezer failures, human errors, or routine inventory management are all examples of TWEs. These events may cause unwanted cell damage due to ice recrystallization, potentially affecting the quality of the RCCs. The aim of this study was to assess if the high glycerol method provides protection to cryopreserved red blood cells (RBCs) against damage incurred during real-world TWEs.
Study
Design/Methods: Thirty previously cryopreserved RCCs, documented as having experienced at least one TWE, were selected and classified according to exposure event: (1) > -65 °C for 34 minutes (n=5), (2) > -65 °C for approximately 2 days reaching a peak temperature of -30 °C (n=23), and (3) exposure to both Event 1 and Event 2 (n=2). Ten previously cryopreserved RCCs documented as having no TWE were selected as controls. All RCCs were thawed (37 °C), deglycerolized and resuspended in AS-3 using the ACP 215 Cell Processor. Units were stored hypothermically and tested at 0, 1, 7, and 14 days post-deglycerolization for RBC quality using an extensive panel of in vitro tests, including hemoglobin (Hb) content, RBC hemolysis, adenosine triphosphate (ATP), RBC indices, and RBC deformability. Multiple group comparisons were performed using Sidak’s multiple comparisons test.
Results/Findings: All RCC units, regardless of TWE exposure, showed no significant differences in quality parameters over 14 days of hypothermic storage. Furthermore at all time points, all RCCs had a hematocrit < 80%, hemoglobin per unit > 35 g/unit, and hemolysis < 0.8% in 85% of the units tested. Conclusions: Our results indicate that exposures to real-world TWEs did not significantly impact the quality of RCCs post-deglycerolization. Further assessments and validation will need to be undertaken by blood centers to determine the impact of the frequency and duration of TWEs on product quality to help define more evidence-based criteria. With these criteria, blood centers could retain valuable and potentially rare RCCs that current blood inventory management strategies require to be discarded after even one exposure to storage temperatures warmer than -65 °C.
Importance of research: Understanding the impact of the frequency and duration of transient warming events on product quality has the potential to prevent unnecessary discard of valuable, rare cryopreserved RCC units.
