Cerebral Autoregulation Monitoring to Reduce Brain Injury from Cardiac Surgery

描述(申请人提供)：心脏手术期间的脑损伤主要是由于脑血栓和/或脑血流量(CBF)减少所致。后者尤其令人担忧的是越来越多的老年外科患者和/或患有脑血管疾病的患者。正常情况下，CBF在一定的血压范围内是生理上自动调节(或保持恒定)的，从而允许与代谢需求相称的稳定的大脑氧气供应。在接受心脏手术并患有脑血管疾病或许多其他疾病的患者中，大脑自动调节功能受损。这种损伤可能导致脑损伤，因为目前在体外循环(CPB)期间以低平均动脉压(通常为50-70 mm Hg)为靶点的做法可能会使脑自我调节受损的患者暴露于脑低灌流。这项研究的假设是，将体外循环期间的平均动脉压控制在高于个人较低自我调节阈值的水平，可以降低心脏手术或术后认知能力下降导致的早期神经系统并发症的风险。脑自动调节将使用软件实时监测，该软件连续比较经颅多普勒测量的脑血流速度和近红外光谱测量的脑血氧饱和度的低频变化之间的关系，使用我们验证的方法。这项研究的主要终点将是临床中风、和/或通过扩散加权磁共振(MR)成像发现的新的缺血性脑损伤和/或术后4至6周基线认知能力下降的综合结果。我们将进一步评估血压低于自我调节极限与精神错乱之间的关系，精神错乱是与发病率和死亡率相关的终点。心脏手术引起的脑损伤是手术死亡率、住院时间延长、医疗费用增加和生活质量下降的重要原因。制定减轻这种并发症负担的战略具有广泛的公共卫生影响，也是NHLBI的任务之一。

DESCRIPTION (provided by applicant): 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 who are undergoing cardiac surgery and have cerebral vascular disease or many other conditions. Such impairment could lead to brain injury because current practices of targeting low mean arterial blood pressure empirically (usually 50-70 mmHg) during cardiopulmonary bypass (CPB) may expose patients with impaired cerebral autoregulation to cerebral hypoperfusion. The hypothesis of this study is that targeting mean arterial pressure during CPB to a level above an individual's lower autoregulatory threshold reduces the risk for early neurologic complications from cardiac surgery or postoperative cognitive decline. Cerebral autoregulation will be monitored in real time by using software that continuously compares the relation between arterial blood pressure and low-frequency changes in transcranial Doppler measured cerebral blood flow velocity as well as cerebral oximetry measured with near infrared spectroscopy using methods we have validated. The primary endpoint of the study will be a composite outcome of clinical stroke, and/or new ischemic brain lesions detected with diffusion-weighted magnetic resonance (MR) imaging, and/or cognitive decline from baseline at 4 to 6 weeks after surgery. We will further assess for a relationship between blood pressure below the limits of autoregulation and delirium, an end-point associated with morbidity and mortality. Brain injury from cardiac surgery is an important source of operative mortality, prolonged hospitalization, increased healthcare 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.