Hold on to your units: Quality of red cell concentrates is only affected after multiple transient warming events

Cryopreserved red cell concentrates (RCCs) glycerolized using a high glycerol (40%) method can be stored below -65°C for up to 30 years; however, units may be inadvertently warmed above -65°C due to freezer failures, human errors, or routine inventory management. RCCs known to have experienced transient warming events (TWEs) or storage temperatures ≥-65°C are frequently discarded.

Six groups of ABO/Rh matched RCCs were pooled-and-split (n = 9), glycerolized using the ACP 215 (Haemonetics), and frozen. Three types of TWEs were performed: (1) "Fast" TWEs (warming at room temperature [RT] to -25°C), (2) "Slow" TWEs (exposure to -25°C for 2 h), and (3) "Thaw" TWEs (single warming to RT). Units (n = 6) were exposed to 0 (control), 1, 10, or 30 "Slow" or "Fast" TWEs. RCCs were deglycerolized using the ACP 215, stored at 1-6°C, and tested at 0, 1, 7, and 14 days post-deglycerolization for red blood cell (RBC) quality.

No significant differences among RCCs over hypothermic storage were found when exposed to "Fast" or "Slow" single or "Thaw" TWEs, although a significant decrease in the quality of RCCs was observed when units were subjected to 10 or more "Fast" or "Slow" TWEs.

Our data suggests the single TWEs examined in this study do not significantly impact the quality of RCCs post-deglycerolization. Based on these observations, TWE exposure considerations should be made on a unit-by-unit basis, with additional policy support for unit retention.