CO2-dependent metabolic modulation in red blood cells stored under anaerobic conditions

BACKGROUNDAnaerobic red blood cell (RBC) storage reduces oxidative damage, maintains adenosine triphosphate (ATP) and 2,3-diphosphoglycerate (DPG) levels, and has superior 24-hour recovery at 6 weeks compared to standard storage. This study will determine if removal of CO2 during O-2 depletion by gas exchange may affect RBCs during anaerobic storage. STUDY DESIGN AND METHODSThis is a matched three-arm study (n=14): control, O-2 and CO2 depleted with Ar (AN), and O-2 depleted with 95%Ar/5%CO2 (AN[CO2]). RBCs in additives AS-3 or OFAS-3 were evenly divided into three bags, and anaerobic conditions were established by gas exchange. Bags were stored at 1 to 6 degrees C in closed chambers under anaerobic conditions or ambient air, sampled weekly for up to 9 weeks for a panel of in vitro tests. A full metabolomics screening was conducted for the first 4 weeks of storage. RESULTSPurging with Ar (AN) results in alkalization of the RBC and increased glucose consumption. The addition of 5% CO2 to the purging gas prevented CO2 loss with an equivalent starting and final pH and lactate to control bags (p>0.5, Days 0-21). ATP levels are higher in AN[CO2] (p<0.0001). DPG was maintained beyond 2 weeks in the AN arm (p<0.0001). Surprisingly, DPG was lost at the same rate in both control and AN[CO2] arms (p=0.6). CONCLUSIONMaintenance of ATP in the AN[CO2] arm demonstrates that ATP production is not solely a function of the pH effect on glycolysis. CO2 in anaerobic storage prevented the maintenance of DPG, and DPG production appears to be pH dependent. CO2 as well as O-2 depletion provides metabolic advantage for stored RBCs.