title: Does colloid-induced plasma hyperviscosity in haemodilution jeopardize perfusion and oxygenation of vital organs?
abstract: METHODS
  The infusion of dextran solutions is associated with haemodilution and, under some conditions, with a slight increase in plasma viscosity. To clarify the compound effects of simultaneous haemodilution and plasma viscosity increases on macro- and microhaemodynamics, we investigated the changes in arterial perfusion (radiolabelled microspheres, 15 microns ø) and oxygenation (tissue Po2) of vital organs using an animal model of plasma hyperviscosity. In nine splenectomized beagles plasma viscosity was increased step by step from 1.06 (baseline) to 2.14, and 2.99 mPa.s by infusion of small amounts (4% of total blood volume) of an ultra-high-molecular-weight dextran (50% w/v, mw: 500,000).
  
  
  RESULTS
  Despite the significant increase in plasma viscosity, cardiac output as well as specific organ blood flows in heart, brain, liver, and muscle rose steadily with each step of viscosity, while the haematocrit declined from 0.31 to 0.24 and 0.20, respectively. Medians of tissue Po2 in liver peaked at a viscosity of 2 mPa.s and returned to baseline values at 3 mPa.s, whereas in non-working skeletal muscle Po2 values were maximal at 3 mPa.s.
  
  
  CONCLUSIONS
  These results indicate that the impact of plasma viscosity on the rheological properties of whole blood is completely offset by the concomitant reduction of haematocrit. Thus, the comparatively minor changes in plasma viscosity observed after prolonged use of clinical dextrans and other colloids in no way compromise the perfusion and oxygenation of vital organs.
authors.affiliation: Institute of Anesthesiology and Intensive Care, Faculty for Clinical Medicine Mannheim, University of Heidelberg, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Krieter
authors.forename: U B
authors.initials: UB
authors.lastname: Brückner
authors.forename: F
authors.initials: F
authors.lastname: Kefalianakis
authors.forename: K
authors.initials: K
authors.lastname: Messmer
mesh_terms: D000818:Animals; D001775:Blood Circulation / Q000187:drug effects*; D001809:Blood Viscosity / Q000187:drug effects*; D001810:Blood Volume; D002302:Cardiac Output / Q000187:drug effects; D002560:Cerebrovascular Circulation / Q000187:drug effects; D003102:Colloids / Q000627:therapeutic use*; D003326:Coronary Circulation / Q000187:drug effects; D003911:Dextrans / Q000627:therapeutic use*; D004195:Disease Models, Animal; D004285:Dogs; D006400:Hematocrit; D006438:Hemodilution; D018056:Hemorheology; D008099:Liver / Q000378:metabolism; D008102:Liver Circulation / Q000187:drug effects; D008863:Microspheres; D008970:Molecular Weight; D018482:Muscle, Skeletal / Q000098:blood supply / Q000187:drug effects / Q000378:metabolism; D010101:Oxygen Consumption / Q000187:drug effects*; D010949:Plasma / Q000187:drug effects*; D010953:Plasma Volume; D013156:Splenectomy
chemical_list: D003102:Colloids; D003911:Dextrans