Does blood viscosity affect cerebral blood flow? A study in a population living in a high-altitude city

Abstract

Background: Viscosity affects flows by increasing resistance to movement; therefore, variations in blood viscosity (BV) levels could modify the cerebral blood flow. Objective: This study aimed to determine the level of correlation between BV and cerebral blood flow in people acclimated to chronic hypoxia who have high BV levels. Methods: Prospective observational study was conducted among clinically healthy young adults living in the city of Cusco (3,399 m above sea level). All participants were examined at low and high shear rates (75 and 300 sec1) to simulate the dynamic component of BV. A transcranial Doppler study of the middle cerebral artery was performed to measure systolic, diastolic, and mean flow velocities (FVs) and resistance and pulsatility indices (PIs). Results: A total of 131 participants were included. The median viscosity levels were 5.01cP [interquartile range (IQR): 4.45, 5.73cP] at 300 sec1 and 6.16 cP [IQR: 5.58, 7.20 cP] at 75 sec1, the mean FV was 57 m/s [IQR: 50, 65 m/s5], and the PI was 0.91 [0.86, 1.02]. BV was negatively correlated with mean FV (r: -0.17, p=0.007), while it showed no correlation with other values of blood flow, resistance, or PI. Conclusions: Changes in BV levels have a minimal impact on the mean FV but not on other parameters. This finding suggests that in young and clinically healthy individuals, there are autoregulation mechanisms that compensate for BV variations, although they are not completely understood.

Circadian and Diurnal Regulation of Cerebral Blood Flow

“…119 Elevated blood viscosity increases blood flow resistance, induces platelet aggregation, and presents a risk factor for cerebrovascular stroke. Blood viscosity minimally impacted CBF in healthy young subjects whose autoregulation was not disrupted, 120 consistent with a preclinical result in healthy animals showing a nonsignificant trend for decreased CBF at elevated viscosity. However, under high CBF states such as hypercapnia and chronic hypoxia, blood viscosity affects CBF, 121 presumably due to an attenuated capacity for compensatory vasodilation.…”

Analysis and evaluation of blood screening testing strategies in Nagqu, Tibet: one of the highest cities in world

“…A significant stride towards improving blood donation and healthcare services in the region occurred in 2017 with the establishment of a blood station in Nagqu City. However, this unique city's population demographics and high-altitude environment introduce distinct challenges that demand careful consideration for ensuring effective and reliable blood screening and donation procedures [4][5][6][7][8][9].…”