Indicators of Erythrocyte Damage after Microwave Warming of Packed Red Blood Cells

Abstract

Abstract Background: Localized overheating of packed red blood cells (PRBCs) after microwave warming with consequent damage to erythrocytes has been reported. We therefore compared possible cellular markers of erythrocyte damage, as measured by flow cytometry, with laboratory indicators of hemolysis to evaluate the effects of microwave warming on PRBCs. Methods: PRBC samples were warmed to room temperature or to 37, 42, 47, 52, or 57 °C in a water bath. Flow cytometry was performed after fluorescein labeling using antibodies to spectrin, Ca2+-ATPase, and Na+-K+-ATPase. The forward-to-sideward scatter (FSC/SSC) ratio and antibody binding were evaluated. Plasma free hemoglobin (FHb) and α-hydroxybutyrate dehydrogenase (HBDH) were measured immediately after heating and after 48 h. In addition, all measurements were made before and after the heating of PRBCs to 35 °C by a microwave blood warmer. Results: Analysis of 15 000 erythrocytes showed a decrease in the FSC/SSC ratio and antibody binding above 47 °C [at 37 °C, median (SD) of 94.2 (7.4) with 0.07 (0.05)% fluorescein-positive; at 52 °C, median (SD) of 177.0 (19.0) with 18.5 (6.4)% positively gated; P <0.001]. FHb [room temperature, 0.3 (0.2) g/L] was increased 2-fold at 37 and 42 °C, 4-fold at 47 °C, and 25-fold at 52 °C. HBDH increased in parallel. Hemolysis markers showed an additional twofold increase 48 h after heating to 42 and 47 °C. Microwave heating to 35 °C did not produce significant changes of any marker. Conclusions: All markers of cellular damage were altered after heating to >47 °C, and a substantial part of hemolysis was delayed. The methodology can be used for future testing of other blood warming devices.