title: Delaying blood transfusion in experimental acute anemia with a perfluorocarbon emulsion.
abstract: BACKGROUND
  To avoid unnecessary blood transfusions, physiologic transfusion triggers, rather than exclusively hemoglobin-based transfusion triggers, have been suggested. The objective of this study was to determine systemic and microvascular effects of using a perfluorocarbon-based oxygen carrier (PFCOC) to maintain perfusion and oxygenation during extreme anemia.
  
  
  METHODS
  The hamster (weight, 55-65 g) window chamber model was used. Two isovolemic hemodilution steps were performed using hydroxyethyl starch, 10%, at normoxic conditions to a hematocrit of 19% (hemoglobin, 5.5 g/dl), the point at which the transfusion trigger was reached. Two additional hemodilution exchanges using the PFCOC (Oxycyte) and increasing the fraction of inspired oxygen to 1.0 were performed to reduce the hematocrit to 11% (hemoglobin, 3.8 g/dl) and 6% (hemoglobin, 2.0 g/dl), respectively. No control group was used in the study because this concentration of hemodilution is lethal with conventional plasma expanders. Systemic parameters, microvascular perfusion, functional capillary density, and oxygen tensions across the microvascular network were measured.
  
  
  RESULTS
  At 6% hematocrit, the PFCOC maintained mean arterial pressure, cardiac output, systemic oxygen delivery, and oxygen consumption. As hematocrit was decreased from 11% to 6%, functional capillary density, calculated microvascular oxygen delivery, and oxygen consumption decreased; and the oxygen extraction ratio was close to 100%. Peripheral tissue oxygenation was not predicted by systemic oxygenation.
  
  
  CONCLUSIONS
  The PFCOC, in conjunction with hyperoxia, was able to sustain organ function and partially provide systemic oxygenation during extreme anemia during the observation period. The PFCOC can work as a bridge until erythrocytes are available for transfusion or when additional oxygen is required, despite the possible limitations in peripheral tissue oxygenation.
authors.affiliation: Department of Bioengineering, University of California, San Diego, La Jolla, California 92093-0412, USA. pcabrales@ucsd.edu
authors.forename: Pedro
authors.initials: P
authors.lastname: Cabrales
authors.forename: Juan
authors.initials: J
authors.lastname: Carlos Briceño
mesh_terms: D000208:Acute Disease; D000740:Anemia / Q000097:blood / Q000188:drug therapy*; D000818:Animals; D001692:Biological Transport; D001802:Blood Substitutes / Q000627:therapeutic use*; D001803:Blood Transfusion; D006224:Cricetinae; D004195:Disease Models, Animal; D005466:Fluorocarbons / Q000627:therapeutic use*; D008297:Male; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D013997:Time Factors
chemical_list: D001802:Blood Substitutes; D005466:Fluorocarbons; D010100:Oxygen