Cell-free layer formation in small arterioles at pathological levels of erythrocyte aggregation

To test our hypothesis that an elevation in the aggregation level of red blood cells found in human pathological conditions will significantly enhance cell-free layer formation in small arterioles.

Visualization of arteriolar blood flow in rat cremaster muscle was carried out in both normal and reduced flow conditions before and after Dextran 500 infusion to simulate physiological and pathological levels of red blood cell aggregation in humans.

Both normalized mean (p < 0.0001) and SD (p < 0.002) of the layer width were significantly enhanced after hyper-aggregation induction in reduced flow conditions (mean pseudoshear rate = 57.3 ± 7.2/sec). Normalized mean and SD of the layer width generally increased with decreasing vessel radius and this effect was most pronounced with hyper-aggregation in reduced flow conditions. The threshold pseudoshear rate at which the layer formation became more pronounced when compared with non-aggregating condition was higher with hyper-aggregation (217/sec) than normal-aggregation induction (139/sec).

Our findings confirmed the formation of a prominent cell-free layer in the arterioles under higher shear conditions at pathological aggregation levels and this effect became more pronounced in smaller arterioles in normalizing the layer to the vessel radius.