Continuous Cerebral Autoregulation Monitoring to Reduce Brain Injury from Cardiac

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性自动调节（或保持恒定），从而使稳定的脑O2供应与代谢需求相称。在患有脑血管疾病的心脏手术患者和许多其他由于其他疾病的患者中，脑自动调节受损。这可能会导致脑损伤，因为目前在心肺转流术期间经验性地以低平均动脉压（通常为50-70 mmHg）为目标的做法可能会使脑自动调节受损的患者暴露于脑灌注不足。该建议的假设是，在体外循环期间将平均动脉压目标设定为高于个体的较低自动调节阈值的水平，可降低接受心脏手术的患者的脑损伤风险。将使用软件进行真实的脑自动调节监测，该软件连续比较动脉血压与经颅多普勒测量的大脑中动脉CBF速度之间的关系，并与近红外光谱测量的脑血氧饱和度之间的关系。研究的主要终点将是临床卒中、认知能力下降和/或弥散加权磁共振（MR）成像检测到的新发缺血性脑病变的综合复合结局。自身调节是由脑阻力血管的反应性介导的。该提案的第二个目的是评估近红外反射光谱是否可用于脑血容量的趋势变化，并提供可靠的血管反应性（血红蛋白体积指数）监测。将使用MR血管造影术评估颅外和颅内动脉狭窄，以控制分析中的该潜在混杂变量。最后，该研究的另一个目的是评估术前经颅多普勒检查主要脑动脉是否可以识别容易发生复合神经终点的患者。近红外血氧饱和度是无创的，连续的，需要很少的护理人员干预，因此，可以广泛用于个性化患者的血压管理在手术期间。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。公共卫生相关性：心脏手术的神经系统并发症是手术死亡率、住院时间延长、医疗费用增加和生活质量下降的重要原因。需要新的护理策略，以避免越来越多的接受心脏手术的老年患者出现并发症。这项研究将评估新的方法，减少脑损伤手术期间从脑血流不足，使用技术，可以广泛使用。

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 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. PUBLIC HEALTH RELEVANCE: Neurological complications from cardiac surgery are an important source of operative mortality, prolonged hospitalization, health care expenditure, and impaired quality of life. New strategies of care are needed to avoid rising complications for the growing number of aged patients undergoing cardiac surgery. This study will evaluate novel methods for reducing brain injury during surgery from inadequate brain blood flow using techniques that could be widely employed.