Cerebral Autoregulation Monitoring to Reduce Brain Injury from Cardiac Surgery

描述（由申请人提供）：心脏手术中的脑损伤主要由脑栓塞和/或脑血流量减少（CBF）引起。对于越来越多的老年和/或患有脑血管疾病的外科病人来说，后者尤其值得关注。正常情况下，脑血流在生理上自动调节（或保持恒定）在血压范围内，允许稳定的脑氧供应与代谢需求相称。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，大脑自身调节功能受损。这种损伤可能导致脑损伤，因为目前在体外循环（CPB）过程中针对低平均动脉血压（通常为50-70 mmHg）的实践可能使脑自动调节受损的患者暴露于脑灌注不足。本研究的假设是，将CPB期间的平均动脉压定位到高于个体较低的自我调节阈值的水平，可以降低心脏手术早期神经系统并发症或术后认知能力下降的风险。大脑自动调节将通过使用软件实时监测，该软件连续比较动脉血压与经颅多普勒测量的脑血流速度的低频变化之间的关系，以及使用我们已经验证的方法用近红外光谱测量的脑血氧饱和度。该研究的主要终点将是临床卒中，和/或扩散加权磁共振（MR）成像检测到的新缺血性脑病变，和/或术后4至6周认知能力较基线下降的综合结果。我们将进一步评估血压低于自我调节极限与谵妄之间的关系，谵妄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。制定战略以减轻这一并发症的负担具有广泛的公共卫生影响，并且属于卫生和健康机构的任务范围。

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.