Venkatraghavan Lashmi, Poublanc Julien, Han Jay S, Sobczyk Olivia, Rozen Casey, Sam Kevin, Duffin James, Mikulis David J, Fisher Joseph A
Department of Anesthesia and Pain Management, University Health Network, University of Toronto, Toronto, Ontario, Canada.
Joint Department of Medical Imaging and the Functional Neuroimaging Laboratory, University Health Network, Toronto, Ontario, Canada.
J Stroke Cerebrovasc Dis. 2018 Feb;27(2):301-308. doi: 10.1016/j.jstrokecerebrovasdis.2017.08.035. Epub 2017 Sep 28.
Impaired cerebrovascular reactivity (CVR) is an important prognostic marker of stroke. Most measures of CVR lack (1) a reproducible vasoactive stimulus and (2) a high time and spatial resolution measure of cerebral blood flow (CBF), particularly for mechanically ventilated patients. The aim of our study was to investigate the feasibility of measuring CVR using sequential gas delivery circuit and gas blender for precise targeting of end-tidal PCO (PetCO), and blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) signal as a surrogate of CBF, in mechanically ventilated patients.
Four patients with known moyamoya disease requiring preoperative CVR measurements under general anesthesia were studied. All patients had standard anesthesia induction and maintenance with intravenous propofol and rocuronium. Patients were intubated and manually ventilated with a self-inflating bag connected to a sequential breathing circuit. A computer-controlled gas blender supplied the gas mixture in proportions to attain target PetCO. BOLD-MRI was performed at 3.0 Tesla magnet. Changes in signal per change in PetCO were calculated, and their magnitude color-coded and mapped onto the anatomic scan to form CVR maps.
CVR studies were successfully performed on all patients, and the CVR values were lower in both gray and white matter bilaterally when compared with healthy volunteers. In addition, CVR maps in 3 patients showed intracerebral steal phenomenon in spite of having had cerebral revascularization procedures, indicating that they are still at risk of cerebral ischemia.
BOLD-MRI CVR studies are feasible in mechanically ventilated patients anesthetized with propofol.
脑血管反应性（CVR）受损是中风的重要预后指标。大多数CVR测量方法缺乏：（1）可重复的血管活性刺激；（2）对脑血流量（CBF）的高时间和空间分辨率测量，特别是对于机械通气患者。我们研究的目的是探讨在机械通气患者中，使用顺序气体输送回路和气体混合器精确靶向呼气末二氧化碳分压（PetCO₂），并以血氧水平依赖性功能磁共振成像（BOLD-MRI）信号作为CBF的替代指标来测量CVR的可行性。
对4例已知烟雾病且需要在全身麻醉下进行术前CVR测量的患者进行研究。所有患者均采用静脉注射丙泊酚和罗库溴铵进行标准麻醉诱导和维持。患者插管后，使用连接到顺序呼吸回路的自动充气袋进行手动通气。计算机控制的气体混合器按比例供应气体混合物以达到目标PetCO₂。在3.0特斯拉磁体上进行BOLD-MRI检查。计算PetCO₂每变化一次时信号的变化，并将其幅度进行颜色编码并映射到解剖扫描上以形成CVR图。
所有患者均成功进行了CVR研究，与健康志愿者相比，双侧灰质和白质的CVR值均较低。此外，3例患者的CVR图显示尽管已经进行了脑血管重建手术，但仍存在脑内盗血现象，表明他们仍有脑缺血风险。
在使用丙泊酚麻醉的机械通气患者中，BOLD-MRI CVR研究是可行的。
