Exposure of cryopreserved red cell concentrates to real-world transient warming events has a negligible impact on quality.

Background: Red cell concentrates (RCCs) may be cryopreserved at Canadian Blood Services (CBS) for up to 10 years; however, inadvertent warming of these units over the prescribed storage temperature (≤ -65°C) may occur. These units may be discarded from inventory to avoid potential adverse transfusion outcomes. This study aimed to assess the quality of RCCs that experienced unintentional transient warming events (TWEs) related to freezer failures.

Study design: Thirty cryopreserved RCCs with known TWEs were selected for this study and classified into three different experimental groups (Event 1 (n = 5) TWE > -65°C for 34 min; Event 2 (n = 23) TWE > -65°C for 48 h; and both Event 1 and Event 2 (n = 2) TWE > -65°C for 34 min and 48 h). Ten additional RCCs with no known TWEs, cryopreserved over the same period, were selected as controls. Thawed RCCs were deglycerolized using the Haemonetics ACP 215, and in vitro quality was assessed throughout hypothermic storage.

Results: RCCs from the control and all three experimental groups met the Canadian Standards Association (CSA) guidelines for hematocrit, total hemoglobin, and hemolysis at expiry. RCCs experiencing a singular TWE had similar in vitro quality to control RCCs.

Discussion: This study's findings revealed that single exposures to specific documented TWEs did not significantly impact the quality of RCCs post-deglycerolization. While units should still be assessed on a case-by-case basis upon TWE, our work provides the first-ever evidence that supports a broader policy of unit retention by blood centers.