Cerebral Autoregulation Monitoring to Reduce Brain Injury from Cardiac Surgery

心脏手术中的脑损伤主要是由于脑血栓和/或脑血流量减少所致 (CBF)。后者尤其令人担忧的是，越来越多的手术患者年龄较大和/或 有脑血管疾病。正常情况下，CBF在生理上自动调节(或保持恒定) 血压范围允许与代谢需求相称的稳定的脑供氧。 患有脑血管疾病的心脏手术患者的大脑自动调节功能受损 在许多其他情况下，由于其他条件。这可能会导致脑损伤，因为目前的靶向做法 体外循环期间平均动脉压低(通常为50-70毫米汞柱)可能 使脑自我调节受损的患者暴露于脑低灌注量。这是一个假设 建议将体外循环期间的平均动脉压控制在 个体较低的自我调节阈值降低了心脏手术患者脑损伤的风险 做手术。大脑自动调节的监测将使用软件实时执行，该软件将连续 动脉血压与大脑中动脉血流速度关系的比较 用经颅多普勒测量，用近红外光谱分析测量脑血氧饱和度。这个 这项研究的主要终点将是临床中风、认知能力下降、 和/或通过扩散加权磁共振(MR)成像检测到新的缺血性脑损害。 自我调节是由大脑阻力血管的反应性介导的。这项提议的次要目的是 评价近红外反射光谱学能否用于脑血液的趋势变化 并提供可靠的血管反应性监测(血红蛋白体积指数)。评估 颅外和颅内动脉狭窄将使用mr血管造影术进行控制。 分析中的潜在混杂变量。最后，这项研究的另一个目的是评估 术前经颅多普勒检查大脑主要动脉可以确定哪些患者容易发生脑血管病变。 复合神经学终点。近红外血氧仪是非侵入性的，连续的，不需要太多的护理- 给予者干预，因此，可以广泛用于个性化的患者血压管理 做手术。心脏手术造成的脑损伤是手术死亡率的重要来源，长期如此 住院、医疗保健支出增加、生活质量受损。制定战略以减少 这一并发症的负担具有广泛的公共卫生影响，属于NHLBI的任务范围。

Brain injury during cardiac surgery results primarily from cerebral embolism and/or reduced cerebral blood flow (CBF). The latter is of particular concern for the growing number of surgical patients who are aged and/or who have cerebral vascular disease. Normally, CBF is physiologically autoregulated (or kept constant) within a range of blood pressures allowing for stable cerebral O2 supply commensurate with metabolic demands. Cerebral autoregulation is impaired in patients undergoing cardiac surgery who have cerebral vascular disease and in many others due to other conditions. This could lead to brain injury since current practices of targeting low mean arterial blood pressure empirically (usually 50-70 mmHg) during cardiopulmonary bypass may expose patients with impaired cerebral autoregulation to cerebral hypoperfusion. The hypothesis of this proposal is that targeting mean arterial pressure during cardiopulmonary bypass to a level above an individual's lower autoregulatory threshold reduces the risk for brain injury in patients undergoing cardiac surgery. Monitoring of cerebral autoregulation will be performed in real time using software that continuously compares the relation between arterial blood pressure and CBF velocity of the middle cerebral artery measured with transcranial Doppler and with cerebral oximetry measured with near infrared spectroscopy. The primary end-point of the study will be a comprehensive composite outcome of clinical stroke, cognitive decline, and/or new ischemic brain lesions detected with diffusion weighted magnetic resonance (MR) imaging. Autoregulation is mediated by reactivity of cerebral resistance vessels. A secondary aim of this proposal is to evaluate whether near infrared reflectance spectroscopy can be used to trend changes in cerebral blood volume and provide a reliable monitor of vascular reactivity (the hemoglobin volume index). Assessments for extra-cranial and intra-cranial arterial stenosis will be performed using MR angiography to control for this potential confounding variable in the analysis. Finally, an additional aim of the study will be to assess whether preoperative transcranial Doppler examination of major cerebral arteries can identify patients who are prone to the composite neurological end-point. Near infrared oximetry is non-invasive, continuous, requires little care- giver intervention and, thus, could be widely used to individualize patient blood pressure management during surgery. Brain injury from cardiac surgery is an important source of operative mortality, prolonged hospitalization, increased health care expenditure, and impaired quality of life. Developing strategies to reduce the burden of this complication has wide public health implications and is within the mission of the NHLBI.