Background/Case Studies: Cryopreserved red cell concentrates (RCCs) glycerolized using a high glycerol (40%) method can be stored below -65 °C for up to 30 years. However, during storage, units may be inadvertently warmed above -65 °C due to freezer failures, human errors, or routine inventory management. Although it has been suggested that high glycerol concentrations may provide protection against these transient warming events (TWEs), this has not been studied extensively.
Study
Design/Methods: ABO/Rh matched RCCs were pooled-and-split (n=9), glycerolized using the ACP 215 Cell Processor, and frozen in a < -65 °C freezer. Three types of TWEs were then performed: (1) “fast” TWEs (warming at room temperature (RT) to -20 °C) (2) “slow” TWEs (exposure to -20 °C for 2 hours) and (3) "thaw" TWEs (warming to room temperature). Units (n=6) were exposed to 0 (control), 1, 10, or 30 TWEs for both the “slow” and “fast” conditions or a single “thaw” and refreeze TWE. RCCs were deglycerolized and resuspended in AS-3 using the ACP 215, stored hypothermically (2 - 6°C) and tested at 0, 1, 7, and 14 days post-deglycerolization for red blood cell (RBC) quality using an extensive panel of in vitro tests. Multiple group comparisons were performed using Sidak’s multiple comparisons test.
Results/Findings: While no significant differences among RCCs over hypothermic storage were found when units were exposed to “fast” or “slow” single or “thaw” TWEs, a significant decrease in the quality of RCCs was observed when units were subjected to ten or more TWEs either “fast” or “slow”. Immediately post-deglycerolization, over 67% of tested units failed to meet standardized guidelines for hemoglobin content (> 35 g/unit). Regardless of the type of TWE, if the number of exposures exceeded ten, more than half of the RCCs failed to meet standardized criteria for hemolysis ( < 0.8%) after one to two weeks of post-thaw hypothermic storage. Conclusions: Common inventory management practices at blood centers involve exposure of units to RT for 30-minute intervals or longer. Exposing RCCs to this level of TWE more than 10 times may impact the quality of RCCs. Additionally, RCCs that are known to have experienced storage temperatures warmer than -65 °C are discarded. Our data however, shows single TWEs do not significantly impact the quality of RCCs post-deglycerolization. Based on these observations, blood centers should review inventory management practices to track TWEs which may result in the unnecessary discard of rare RCCs.
Importance of research: The research presented within this abstract showcases to our knowledge, the first controlled quality monitoring study of transiently warmed cryopreserved RCCs ever conducted. It was undertaken to improve our understanding of the impacts of TWEs on red cell quality in order to inform decisions surrounding the management of frozen RCC inventories.
