title: Indicators of erythrocyte damage after microwave warming of packed red blood cells.
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 degrees C in a water bath. Flow cytometry was performed after fluorescein labeling using antibodies to spectrin, Ca(2+)-ATPase, and Na(+)-K(+)-ATPase. The forward-to-sideward scatter (FSC/SSC) ratio and antibody binding were evaluated. Plasma free hemoglobin (FHb) and alpha-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 degrees C by a microwave blood warmer.
  
  
  RESULTS
  Analysis of 15000 erythrocytes showed a decrease in the FSC/SSC ratio and antibody binding above 47 degrees C [at 37 degrees C, median (SD) of 94.2 (7.4) with 0.07 (0.05)% fluorescein-positive; at 52 degrees 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 degrees C, 4-fold at 47 degrees C, and 25-fold at 52 degrees C. HBDH increased in parallel. Hemolysis markers showed an additional twofold increase 48 h after heating to 42 and 47 degrees C. Microwave heating to 35 degrees C did not produce significant changes of any marker.
  
  
  CONCLUSIONS
  All markers of cellular damage were altered after heating to >47 degrees C, and a substantial part of hemolysis was delayed. The methodology can be used for future testing of other blood warming devices.
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, University Hospital, 35385 Giessen, Germany. Jan.Hirsch@chiru.med.uni-giessen.de
authors.forename: Jan
authors.initials: J
authors.lastname: Hirsch
authors.forename: Axel
authors.initials: A
authors.lastname: Menzebach
authors.forename: Ingeborg Dorothea
authors.initials: ID
authors.lastname: Welters
authors.forename: Gerald Volker
authors.initials: GV
authors.lastname: Dietrich
authors.forename: Norbert
authors.initials: N
authors.lastname: Katz
authors.forename: Gunter
authors.initials: G
authors.lastname: Hempelmann
mesh_terms: D015415:Biomarkers / Q000097:blood; D004912:Erythrocytes / Q000737:chemistry* / Q000166:cytology; D005434:Flow Cytometry; D006361:Heating; D006461:Hemolysis; D006801:Humans; D008872:Microwaves
chemical_list: D015415:Biomarkers