Regional hypoxic cerebral vasodilation facilitated by diameter changes primarily in anterior versus posterior circulation

Abstract

The inability to quantify cerebral blood flow and changes in macrocirculation cross-sectional area in all brain regions impedes robust insight into hypoxic cerebral blood flow control. We applied four-dimensional flow magnetic resonance imaging to quantify cerebral blood flow (ml • min) and cross-sectional area (mm) simultaneously in 11 arteries. In healthy adults, blood pressure, O Saturation (SpO), and end-tidal CO were measured at baseline and steady-state hypoxia (FiO = 0.11). We investigated left and right: internal carotid, vertebral, middle, anterior, posterior cerebral arteries, and basilar artery. Hypoxia (SpO = 80±2%) increased total cerebral blood flow from 621±38 to 742±50 ml • min ( p < 0.05). Hypoxia increased cerebral blood flow, except in the right posterior cerebral arteries. Hypoxia increased cross-sectional area in the anterior arteries (left and right internal carotid arteries, left and right middle, p < 0.05; left and right anterior p = 0.08) but only the right vertebral artery of the posterior circulation. Nonetheless, relative cerebral blood flow distribution and vascular reactivity (Δ%cerebral blood flow • ΔSpO) were not different between arteries. Collectively, moderate hypoxia: (1) increased cerebral blood flow, but relative distribution remains similar to normoxia, (2) evokes similar vascular reactivity between 11 arteries, and (3) increased cross-sectional area primarily in the anterior arteries. This study provides the first wide-ranging, quantitative, functional and structural data regarding intracranial arteries during hypoxia in humans, highlighting cerebral blood flow regulation of microcirculation and macrocirculation differs between anterior and posterior circulation.

Sodium nitroprusside dilates cerebral vessels and enhances internal carotid artery flow in young men

“…) and in response to hypoxia (Mikhail Kellawan et al . ). We did not evaluate whether SNP affects CBF when MAP is preserved, but as CO increased with administration of SNP there was no indication for a central limitation to CBF.…”

Vertebral Artery Diameter and Flow: Nature or Nurture

“…The main limitation of our study is the lack of confirmation with MR imaging that has a higher specificity and sensitivity for VA diameter measurement . However, B‐mode ultrasound was performed by the same expert professional sonographers in order to visualize the VA according to their best knowledge.…”

“…21,26 The main limitation of our study is the lack of confirmation with MR imaging that has a higher specificity and sensitivity for VA diameter measurement. [27][28][29][30] However, B-mode ultrasound was performed by the same expert professional sonographers in order to visualize the VA according to their best knowledge. Moreover, evidence supports the use of Color Doppler ultrasound for cerebral blood flow velocity measurements in the VA against MRI, which is not the case for VA diameter measurement.…”

Specific effect of hypobaria on cerebrovascular hypercapnic responses in hypoxia

“…On the contrary, increases in PaCO 2 and in blood pH are major factors increasing CBF via a common pathway, due to their vasoactive effects (Willie, Smith, et al, 2014;Willie, Tzeng, et al, 2014). When exposed to acute hypoxia (from minutes to hours), cerebral vasodilatation (i.e., increase in MCA diameter) occurs to limit the cDO 2 decrease (Imray et al, 2014;Mikhail Kellawan, Harrell, Roldan-Alzate, Wieben, & Schrage, 2017;Wilson et al, 2011). This regulation leads to an increase in cerebral oxygen delivery by 0.5%-2.5% of SaO 2 decrease (Cohen, Alexander, Smith, Reivich, & Wollman, 1967;Jensen, Sperling, Severinghaus, & Lassen, 1996;Willie et al, 2012).…”