Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center, Salt Lake City, Utah.
Department of Internal Medicine, University of Utah, Salt Lake City, Utah.
Am J Physiol Regul Integr Comp Physiol. 2020 Jul 1;319(1):R33-R42. doi: 10.1152/ajpregu.00025.2020. Epub 2020 May 13.
Cerebral blood flow (CBF) is commonly inferred from blood velocity measurements in the middle cerebral artery (MCA), using nonimaging, transcranial Doppler ultrasound (TCD). However, both blood velocity and vessel diameter are critical components required to accurately determine blood flow, and there is mounting evidence that the MCA is vasoactive. Therefore, the aim of this study was to employ imaging TCD (ITCD), utilizing color flow images and pulse wave velocity, as a novel approach to measure both MCA diameter and blood velocity to accurately quantify changes in MCA blood flow. ITCD was performed at rest in 13 healthy participants (7 men/6 women; 28 ± 5 yr) with pharmaceutically induced vasodilation [nitroglycerin (NTG), 0.8 mg] and without (CON). Measurements were taken for 2 min before and for 5 min following NTG or sham delivery (CON). There was more than a fivefold, significant, fall in MCA blood velocity in response to NTG (∆-4.95 ± 4.6 cm/s) compared to negligible fluctuation in CON (∆-0.88 ± 4.7 cm/s) ( < 0.001). MCA diameter increased significantly in response to NTG (∆0.09 ± 0.04 cm) compared with the basal variation in CON (∆0.00 ± 0.04 cm) ( = 0.018). Interestingly, the product of the NTG-induced fall in MCA blood velocity and increase in diameter was a significant increase in MCA blood flow following NTG (∆144 ± 159 ml/min) compared with CON (∆-5 ± 130 ml/min) ( = 0.005). These juxtaposed findings highlight the importance of measuring both MCA blood velocity and diameter when assessing CBF and document ITCD as a novel approach to achieve this goal.
脑血流（CBF）通常通过使用非成像经颅多普勒超声（TCD）测量大脑中动脉（MCA）中的血流速度来推断。然而，准确确定血流量需要同时考虑血流速度和血管直径，并且有越来越多的证据表明 MCA 具有血管活性。因此，本研究的目的是采用成像 TCD（ITCD），利用彩色血流图像和脉搏波速度，作为一种新的方法来测量 MCA 直径和血流速度，以准确量化 MCA 血流量的变化。在 13 名健康参与者（7 名男性/6 名女性；28 ± 5 岁）中进行 ITCD 静息检查，并用药物诱导血管扩张（硝酸甘油（NTG），0.8 mg）和不扩张（CON）。在 NTG 或假给药（CON）之前和之后的 5 分钟内，进行了 2 分钟的测量。与 CON 中几乎没有波动（∆-0.88 ± 4.7 cm/s）相比，NTG 引起 MCA 血流速度显著下降超过五倍（∆-4.95 ± 4.6 cm/s）（< 0.001）。与 CON 中基础变化（∆0.00 ± 0.04 cm）相比，NTG 引起 MCA 直径显著增加（∆0.09 ± 0.04 cm）（ = 0.018）。有趣的是，NTG 引起的 MCA 血流速度下降与直径增加的乘积是 NTG 后 MCA 血流增加（∆144 ± 159 ml/min）与 CON 相比（∆-5 ± 130 ml/min）的显著增加（ = 0.005）。这些并列的发现强调了在评估 CBF 时同时测量 MCA 血流速度和直径的重要性，并记录了 ITCD 作为实现这一目标的新方法。
