Local shear stress and brachial artery functions in end-stage renal disease

Physiologic laminar shear stress (SS) is crucial for normal vascular structure and function. As a result of anemia-related lower whole-blood viscosity (WBV), SS could be reduced in patients with ESRD and might be associated with arterial functional alterations. In 44 patients with ESRD and 25 control subjects, brachial artery (BA) compliance and BA diameter changes (flow-mediated dilation [FMD[) were evaluated in response to local shear rate and SS changes during hand warming-induced hyperemia. Patients with ESRD and control subjects had similar BA blood flow, but SS was lower in patients with ESRD (P < 0.001), with lower shear rate (P < 0.01) and lower WBV (P < 0.0001). In control subjects, SS was positively (and physiologically) correlated with arterial diameter (P < 0.001). In contrast, in patients with ESRD, larger arterial diameter was associated with low SS (P < 0.05) and increased arterial wall elastic modulus (P < 0.001). Anemia-associated low WBV aggravates low shear rate, further contributing to SS reduction. These abnormalities were associated with decreased vasodilating response to endothelial mechanical stimulation. Compared with control subjects, BA compliance and FMD increases in response to hand warming-induced increased SS were lower in ESRD patients (P < 0.01), whereas their BA diameter response to glyceryl trinitrate did not differ. The long-term WBV and SS increases after anemia correction improved FMD (P < 0.01) and BA compliance (P < 0.05) and heightened arterial wall sensitivity to mechanical stimulation. Maintenance low SS as a result of anemia could play an indirect role in arterial dysfunction in patients with ESRD.