CEREBRAL AUTOREGULATION MONITORING TO REDUCE BRAIN INJURY FROM CARDIAC SURGERY

描述（由申请方提供）：心脏手术期间的脑损伤主要由脑栓塞和/或脑血流量（CBF）减少引起。后者对于越来越多的老年和/或患有脑血管疾病的手术患者尤其令人担忧。正常情况下，CBF在一定的血压范围内进行生理自动调节（或保持恒定），从而使稳定的脑O2供应与代谢需求相称。在接受心脏手术和患有脑血管疾病或许多其他疾病的患者中，脑自动调节受损。这种损害可能导致脑损伤，因为目前在心肺转流（CPB）期间经验性地以低平均动脉血压（通常为50-70 mmHg）为目标的做法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期间的平均动脉压目标设定为高于个体自动调节阈值下限的水平，可降低心脏手术或术后认知功能下降导致的早期神经系统并发症的风险。将使用软件对脑自动调节进行真实的实时监测，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，以及使用我们已验证的方法用近红外光谱测量的脑血氧饱和度。研究的主要终点将是临床卒中和/或弥散加权磁共振（MR）成像检测到的新发缺血性脑病变和/或术后4 - 6周较基线的认知下降的复合结局。我们将进一步评估血压低于自动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、住院时间延长、医疗费用增加和生活质量受损的重要原因。制定战略，以减少这种并发症的负担具有广泛的公共卫生影响，是在NHLBI的使命。

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.