In Vivo Hemodynamics and Red Blood Cell Aggregation

2011 ◽  
pp. 173-222
Keyword(s):  
Blood Cell ◽  
Red Blood Cell ◽  
Cell Aggregation ◽  
Red Blood Cell Aggregation ◽  
Blood Cell Aggregation

Erythrocyte margination and sedimentation in skeletal muscle venules

2001 ◽  
Vol 281 (2) ◽  
pp. H951-H958 ◽  
Author(s):  
Jeffrey J. Bishop ◽  
Patricia R. Nance ◽  
Aleksander S. Popel ◽  
Marcos Intaglietta ◽  
Paul C. Johnson
Keyword(s):  
Skeletal Muscle ◽  
Arterial Pressure ◽  
Blood Cell ◽  
Red Blood Cell ◽  
Plasma Layer ◽  
Cell Aggregation ◽  
Cell Column ◽  
Red Blood Cell Aggregation ◽  
Blood Cell Aggregation

Previous studies in skeletal muscle of the dog and cat have shown that venous vascular resistance changes inversely with blood flow and may be due mainly to red blood cell aggregation, a phenomenon present in these species. To determine whether red blood cell axial migration and sedimentation contribute to this effect, we viewed either vertically or horizontally oriented venules of the rat spinotrapezius muscle with a horizontally oriented microscope during acute arterial pressure reduction. With normal (nonaggregating) rat blood, reduction of arterial pressure did not significantly change the relative diameter of the red blood cell column with respect to the venular wall. After induction of red blood cell aggregation in the rat by infusion of Dextran 500, red blood cell column diameter decreased up to 35% at low pseudoshear rates (below ∼5 s−1); the magnitude was independent of venular orientation. In vertically oriented venules, the plasma layer was symmetrical, whereas in horizontally oriented venules, the plasma layer formed near the upper wall. We conclude that, although red blood cell axial migration and sedimentation develop in vivo, they occur only for larger flow reductions than are needed to elicit changes in venous resistance.

Effect of erythrocyte aggregation on velocity profiles in venules

2001 ◽  
Vol 280 (1) ◽  
pp. H222-H236 ◽  
Author(s):  
Jeffrey J. Bishop ◽  
Patricia R. Nance ◽  
Aleksander S. Popel ◽  
Marcos Intaglietta ◽  
Paul C. Johnson
Keyword(s):  
Blood Cell ◽  
Red Blood Cell ◽  
Cell Aggregation ◽  
Velocity Profiles ◽  
Erythrocyte Aggregation ◽  
Shear Rates ◽  
Red Blood Cell Aggregation ◽  
Venous Resistance ◽  
Blood Cell Aggregation

A recent whole organ study in cat skeletal muscle showed that the increase in venous resistance seen at reduced arterial pressures is nearly abolished when the muscle is perfused with a nonaggregating red blood cell suspension. To explore a possible underlying mechanism, we tested the hypothesis that red blood cell aggregation alters flow patterns in vivo and leads to blunted red blood cell velocity profiles at reduced shear rates. With the use of fluorescently labeled red blood cells in tracer quantities and a video system equipped with a gated image intensifier, we obtained velocity profiles in venous microvessels (45–75 μm) of rat spinotrapezius muscle at centerline velocities between 0.3 and 14 mm/s (pseudoshear rates 3–120 s−1) under normal (nonaggregating) conditions and after induction of red blood cell aggregation with Dextran 500. Profiles are nearly parabolic (Poiseuille flow) over this flow rate range in the absence of aggregation. When aggregation is present, profiles are parabolic at high shear rates and become significantly blunted at pseudoshear rates of 40 s−1 and below. These results indicate a possible mechanism for increased venous resistance at reduced flows.

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