Clinical Hemorheology and Microcirculation - Volume 35, issue 1-2

Authors: Forconi, Sandro

Article Type: Other

Citation: Clinical Hemorheology and Microcirculation, vol. 35, no. 1-2, pp. 1-3, 2006

Authors: Forconi, Sandro

Article Type: Other

Citation: Clinical Hemorheology and Microcirculation, vol. 35, no. 1-2, pp. 5-5, 2006

Authors: Forconi, Sandro

Article Type: Other

Citation: Clinical Hemorheology and Microcirculation, vol. 35, no. 1-2, pp. 7-9, 2006

Authors: Boisseau, Michel René

Article Type: Other

Citation: Clinical Hemorheology and Microcirculation, vol. 35, no. 1-2, pp. 11-16, 2006

Authors: Antonova, N. | Riha, P.

Article Type: Research Article

Abstract: The electrorheological (ER) properties of blood indicate changes in the blood rheological behaviour due to imposition of electric field. The present work identifies and quantifies ER properties of blood at different shear rates and at different local structure of the flow field. A concurrent measurement system, based on a Contraves Low Shear 30 rotational rheometer was used in this study. It includes a pair of cylindrically shaped platinum electrodes, embedded into the wall of a resin replica of the Couette type flow chamber of the rheometer, constructed for conductivity measurement, and associated software (Data acquisition system). The relationship between the …whole blood and plasma conductivity (the main active component of blood impedance) was studied in parallel with the changes in the rheological behaviour under steady and transient flow conditions. The time variation of blood conductivity at different flow regimes and the dependences of the apparent whole blood and plasma viscosity were investigated in the presence and absence of an electric field of 2 kHz. The results show that blood conductivity is strongly dependent on the blood factors considered and that any application using blood conductivity measurement should take into account the effect of flow, shear rates and hematocrit. The results also show that valuable information on the mechanical properties of blood can be obtained, in particular concerning the structuring and kinetics of “rouleaux formation”. Show more

Citation: Clinical Hemorheology and Microcirculation, vol. 35, no. 1-2, pp. 19-29, 2006

Authors: Gori, Tommaso | Lisi, Monica | Forconi, Sandro

Article Type: Research Article

Abstract: Ischemia and reperfusion (IR) injury causes a variety of changes in tissue homeostasis that lead to necrosis and/or programmed cell death. Due to its strategic location at the luminal surface of vessels, the vascular endothelium is particularly sensitive to IR. In particular, endothelial biosynthetic activities (and their protective effects) appear to be impaired by the oxidative burst induced by a sudden increase in oxygen free radical species upon reperfusion. Importantly, this endothelial damage can be easily assessed in vivo in humans by measuring endothelium-dependent vasorelaxation. Paradoxically, recent studies have emphasized the central role of free radicals (including oxygen free radicals …and nitric oxide) also in a protective process, denominated ischemic preconditioning, i.e. a condition whereby a given stimulus can increase the tolerance of a tissue to IR damage. We discuss the role of the endothelium in determining the mechanism of IR injury, and on the other side, the effect of IR injury on endothelial function. In particular, we focus on the role of reactive free radicals in endothelial IR injury and in the development of ischemic preconditioning. Show more

Citation: Clinical Hemorheology and Microcirculation, vol. 35, no. 1-2, pp. 31-34, 2006

Authors: Meiselman, Herbert J. | Baskurt, Oguz K.

Article Type: Research Article

Abstract: The rheologic characteristics of blood and its formed elements continue to be of basic science and clinical interest, with numerous publications dealing with topics such as blood and plasma viscosity, RBC aggregation and cell deformability. Alterations of blood's rheologic behavior in pathologic states have been extensively studied, with the findings usually indicating changes assumed to be detrimental to tissue perfusion (e.g., increased RBC aggregation). However, the current literature contains relatively few studies dealing with two important areas: (1) relations between altered rheologic behavior and in vivo hemodynamics; (2) the effects of therapy in those clinical states associated with altered rheologic …behavior. This paper presents brief and selective comments on the assumed importance of two rheologic “abnormalities” (i.e., increased plasma viscosity, increased RBC aggregation), and on whether clinical therapy in diabetes, hypertension and sepsis leads to normalization of the “abnormalities”. Finally, a few gratuitous comments are presented regarding possible future directions in the field of hemorheology and hemodynamics. Show more

Keywords: hemodynamics, hemorheology, RBC aggregation, therapy, viscosity

Citation: Clinical Hemorheology and Microcirculation, vol. 35, no. 1-2, pp. 37-43, 2006

Authors: Baskurt, O.K. | Yalcin, O. | Gungor, F. | Meiselman, H.J.

Article Type: Research Article

Abstract: It is well known that the hematocrit in microvessels with diameters smaller than 1000 μm is lower than either venous or arterial hematocrit, thereby resulting in significantly lower mean hematocrit values for vessels perfusing a given tissue (i.e., lower tissue hematocrit). The mechanisms that underlie this reduction of microvascular hematocrit include axial migration, plasma skimming and the Fahraeus Effect. It has been previously demonstrated in rats that a linear hematocrit gradient normally exists through the thickness of the left ventricular myocardium, and that this gradient is sensitive to alterations of the rheological properties of the circulating blood. The gradient is …abolished if the RBC in the perfusate are rigid; fibrinogen infusions, and thus increases of both plasma viscosity and RBC aggregation, also affect this gradient. In a new series of studies, it has been observed that enhanced RBC aggregation affects the myocardial hematocrit gradient regardless of alterations of plasma viscosity. Although the exact mechanisms responsible for the myocardial hematocrit gradient, as well as its physiological significance, are not yet clearly known, it is possible to speculate that alterations in local hematocrit could adversely affect myocardial perfusion and function. Show more

Keywords: Tissue hematocrit, microvascular hematocrit, erythrocyte deformability, erythrocyte aggregation

Citation: Clinical Hemorheology and Microcirculation, vol. 35, no. 1-2, pp. 45-50, 2006

Authors: Martini, J. | Carpentier, B. | Chávez Negrete, A. | Cabrales, P. | Tsai, A.G. | Intaglietta, M.

Article Type: Research Article

Abstract: Increased plasma and blood viscosity are usually associated with pathological conditions; however there are several situations in which the elevation of both parameters results in increased perfusion and the lowering of peripheral vascular resistance. In extreme hemodilution blood viscosity is too low and insufficient to maintain functional capillary density, a problem that in experimental studies is shown to be corrected by increasing plasma viscosity up to 2.2 cP. This effect is mediated by Nitric oxide (NO) production via restoration of shear stress at the endothelium as shown by microelectrode perivascular measurements of NO concentration. Moderate elevations of blood viscosity by …increasing hematocrit (∼10% of baseline) result in reductions of blood pressure by 10 mmHg of baseline. This effect is also NO mediated since it is absent after N-nitro-L-arginine methyl ester (L-NAME) treatment and in endothelial NO synthase deficient mice. These results show that the rheological properties of plasma affect vessel diameter in the microcirculation leading to counterintuitive responses to the increase in viscosity. Show more

Keywords: Nitric oxide, shear stress, hemodilution, hemoconcentration

Citation: Clinical Hemorheology and Microcirculation, vol. 35, no. 1-2, pp. 51-57, 2006

Authors: Nemeth, N. | Soukup, J. | Menzel, M. | Henze, D. | Clausen, T. | Rieger, A. | Holz, C. | Scharf, A. | Hanisch, F. | Furka, I. | Miko, I.

Article Type: Research Article

Abstract: Using a well defined pig model, we investigated whether cerebral hypertension and hypotension influence hemorheological factors. After surgical preparation and stabilization, periods of hyperventilation, controlled periods of cerebral perfusion pressure increases and decreases were utilized. After each period, blood samples were collected from the cannulated femoral artery and vein, and from the superior sagittal sinus. Erythrocyte deformability, whole blood and plasma viscosity and hematological parameters were determined. Erythrocyte deformability significantly worsened in arterial samples after hypertension and hypotension, and in sinus samples it was impaired after hypotension period. Hematocrit significantly increased in arterial and sinus samples during hypertensive period, accompanied …by similar alterations in whole blood viscosity. We conclude that hemodynamic changes caused by hyperventilation, hyper- or hypotension can influence hemorheological factors, and suggest that the rheological alterations can affect local hemodynamic and metabolic conditions. Show more

Keywords: Hyperventilation, cerebral perfusion, cerebral blood flow, hemorheology

Citation: Clinical Hemorheology and Microcirculation, vol. 35, no. 1-2, pp. 59-65, 2006