Affiliations: Department of Operative Techniques and Surgical Research, Institute of Surgery, Medical and Health Science Center, University of Debrecen, Hungary | Department of Physiology and Biophysics, University of Southern California, Keck School of Medicine, Los Angeles, CA, USA | Auguszta Surgical Center, Institute of Surgery, Medical and Health Science Center, University of Debrecen, Hungary | Department of Physiology, Akdeniz University, Faculty of Medicine, Antalya, Turkey
Note: [] Address for correspondence: Dr Norbert Nemeth, Department of Operative Techniques and Surgical Research, Medical and Health Science Center, University of Debrecen, Nagyerdei krt. 98, H-4032 Debrecen, Hungary. Tel./Fax: +36 52 416 915; E-mail: [email protected].
Abstract: Hematocrit (Hct) is the major determinant of whole blood viscosity and of its oxygen binding capacity: with increasing Hct, viscosity increases exponentially and oxygen capacity increases linearly. Thus, the theoretical oxygen transport potential of blood, as indexed by the ratio of Hct to viscosity (Hct/viscosity), generally yields a curve concave to the Hct axis with a maximum at an “optimal hematocrit” value. This study analyzed relations between Hct, blood viscosity and shear rate for rats and dogs to explore whether different optima exist for Hct or Hct/viscosity. Our results reveal differences depending on both shear rate and species: at equal Hct, rats had higher blood viscosity and thus lower Hct/viscosity levels. Optimum values for Hct/viscosity were markedly different between the two species at shear rates of 90 and 200 s−1. Conversely, Hct/viscosity data at 10 s−1 did not exhibit an optimum but rather a linear decrease of the ratio with increasing hematocrit. Relations between Hct and blood viscosity thus differ among animal species. Inasmuch as animal studies are often utilized as an aid to understanding hemorheological aspects of clinical conditions and/or therapy, evaluating Hct/viscosity ratios may be a useful supplementary tool for research focused on various physiological and patho-physiological processes.
Keywords: Optimal hematocrit, blood viscosity, dog, inter-species differences, rat
DOI: 10.3233/BIR-2009-0533
Journal: Biorheology, vol. 46, no. 2, pp. 155-165, 2009
