Background: Packed red cells (RBCs) warmed above 10 degrees C are generally discarded. Few data exist on the degree of accelerated metabolism and increased hemolysis of packed RBCs allowed to warm.
Study design and methods: Twenty-four CPDA-1 packed RBC units were combined in 3-unit pools and subdivided into 2 test units and a control unit. One test unit from each pool was warmed to 25 degrees C for 24 hours on Day 6 and the other test unit was warmed on Day 20; control units were maintained at 1 to 6 degrees C. RBC and supernatant chemistries and RBC morphology were measured weekly (Days 0, 7, 14, 21, and 28) and on the day before warming (Days 6 and 20).
Results: Warming CPDA-1 packed RBCs accelerated the catabolism of glucose 10-fold and produced concentrations of glucose, lactate, and ATP after 25 days of storage that were equivalent to those in unwarmed units at 35 days. Supernatant sodium and potassium concentrations were corrected partially with warming. RBC morphology transiently normalized with warming and without increased hemolysis; no bacteria growth was detected.
Conclusion: One day of 25 degrees C storage of CPDA-1 packed RBCs accelerates essential metabolite break-down equivalent to 10 days of storage at 1 to 6 degrees C. It does not appear to matter whether the packed RBCs are warmed on Day 6 or Day 20. This information may be useful in determining the acceptability of blood allowed to warm above 10 degrees C.