Department of Internal Medicine, Waterlandziekenhuis, Purmerend.
Medical Biology, Laboratory for Cardiovascular Physiology, AMC Center for Heart Failure Research, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
Eur J Neurol. 2018 Nov;25(11):1365-e117. doi: 10.1111/ene.13737. Epub 2018 Jul 31.
Cerebrovascular responses to head-of-bed positioning in patients with acute ischaemic stroke are heterogeneous, questioning the applicability of general recommendations on head positioning. Cerebral autoregulation is impaired to various extents after acute stroke, although it is unknown whether this affects cerebral perfusion during posture change. We aimed to elucidate whether the cerebrovascular response to head position manipulation depends on autoregulatory performance in patients with ischaemic stroke.
The responses of bilateral transcranial Doppler ultrasound-determined cerebral blood flow velocity (CBFV) and local cerebral blood volume (CBV), assessed by near-infrared spectroscopy of total hemoglobin tissue concentration ([total Hb]), to head-of-bed lowering from 30° to 0° were determined in 39 patients with acute ischaemic stroke and 17 reference subjects from two centers. Cerebrovascular autoregulatory performance was expressed as the phase difference of the arterial pressure-to-CBFV transfer function.
Following head-of-bed lowering, CBV increased in the reference subjects only ([total Hb]: + 2.1 ± 2.0 vs. + 0.4 ± 2.6 μM; P < 0.05), whereas CBFV did not change in either group. CBV increased upon head-of-bed lowering in the hemispheres of patients with autoregulatory performance <50th percentile compared with a decrease in the hemispheres of patients with better autoregulatory performance ([total Hb]: +1.0 ± 1.3 vs. -0.5 ± 1.0 μM; P < 0.05). The CBV response was inversely related to autoregulatory performance (r = -0.68; P < 0.001) in the patients, whereas no such relation was observed for CBFV.
This study is the first to provide evidence that cerebral autoregulatory performance in patients with acute ischaemic stroke affects the cerebrovascular response to changes in the position of the head.
急性缺血性脑卒中患者床头抬高后的脑血管反应存在异质性，这使得一般的床头抬高建议的适用性受到质疑。尽管急性脑卒中后脑自动调节功能受到不同程度的损害，但尚不清楚这是否会影响体位变化时的脑灌注。我们旨在阐明急性缺血性脑卒中患者的脑血管对头部位置操作的反应是否取决于自动调节功能。
本研究在两个中心共纳入 39 例急性缺血性脑卒中患者和 17 例参考对象，通过经颅多普勒超声测定双侧大脑中动脉血流速度（CBFV），并采用近红外光谱法测定局部脑血容量（CBV），评估从 30°降低至 0°时头部位置的变化对脑血流的影响。脑自动调节功能通过动脉压与 CBFV 传递函数的相位差来表示。
参考对象在床头降低后仅出现 CBV 增加（[total Hb]：+2.1±2.0 μM 比+0.4±2.6 μM；P<0.05），而两组的 CBFV 均无变化。与自动调节功能较好的患者相比，自动调节功能<50%百分位患者的患侧半球在床头降低时出现 CBV 增加（[total Hb]：+1.0±1.3 μM 比-0.5±1.0 μM；P<0.05）。在患者中，CBV 反应与自动调节功能呈负相关（r=-0.68；P<0.001），而 CBFV 则无此相关性。
本研究首次提供证据表明，急性缺血性脑卒中患者的自动调节功能会影响头部位置变化时的脑血管反应。
