Nollert G, Shin'oka T, Jonas R A
Clinic of Cardiac Surgery, Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.
Thorac Cardiovasc Surg. 1998 Jun;46(3):167-75. doi: 10.1055/s-2007-1010220.
Neuropsychological and neurological deficits are still major causes of mortality and morbidity after cardiac operations and are thought to be caused by embolism and cerebral hypoxia. Near-infrared spectrophotometry (NIRS) is a promising method for non-invasive monitoring of cerebral oxygenation and hemodynamics. Different devices provide information on changes of oxygenated (HbO2) and deoxygenated hemoglobin (Hb), oxidized cytochrome aa3 (CytOx) or regional oxygen saturation (rSO2). NIRS has been applied to patients during adult and pediatric cardiovascular surgery with and without deep hypothermic circulatory arrest (DHCA). In most of the studies, significant changes in cerebral oxygenation were detected by NIRS. NIRS measurements were influenced by the cerebral oxygen metabolism and the operative management. However, clinical, experimental, and theoretical issues raise doubts as to the clinical relevance of the hemoglobin saturation (HbO2, Hb, rSO2 signals) during hypothermia and alkalosis, because the oxygen affinity of hemoglobin increases and a high saturation might simply reflect the inadequate oxygen transport into cells. In contrast, recent experiments have proved a high correlation between the CytOx signal and the MRS parameters nucleoside triphosphate and phosphocreatine. Histological damage was significantly related to the lowest CytOx value; in a clinical study it predicted impaired neuropsychological outcome. Therefore, the CytOx signal is of great interest for future studies. NIRS must prove its ability to diagnose cerebral hypoxia consistently during cardiac surgery in a large patient study before this method is brought into routine clinical practice. Absolute quantification and definitions of critical oxygenation margins will be helpful for this goal.
神经心理学和神经功能缺损仍是心脏手术后死亡率和发病率的主要原因，被认为是由栓塞和脑缺氧所致。近红外分光光度法（NIRS）是一种用于无创监测脑氧合和血流动力学的有前景的方法。不同的设备可提供有关氧合血红蛋白（HbO2）、脱氧血红蛋白（Hb）、氧化细胞色素aa3（CytOx）或局部氧饱和度（rSO2）变化的信息。NIRS已应用于成人和小儿心血管手术患者，无论是否使用深低温停循环（DHCA）。在大多数研究中，NIRS检测到脑氧合有显著变化。NIRS测量受脑氧代谢和手术管理的影响。然而，临床、实验和理论问题对低温和碱中毒期间血红蛋白饱和度（HbO2、Hb、rSO2信号）的临床相关性提出了质疑，因为血红蛋白的氧亲和力增加，高饱和度可能仅仅反映了氧向细胞内转运不足。相反，最近的实验证明CytOx信号与磁共振波谱参数三磷酸核苷和磷酸肌酸之间有高度相关性。组织学损伤与最低CytOx值显著相关；在一项临床研究中，它预测了神经心理学预后受损。因此，CytOx信号对未来研究具有重要意义。在将该方法应用于常规临床实践之前，NIRS必须在一项大型患者研究中证明其在心脏手术期间持续诊断脑缺氧的能力。绝对定量和临界氧合边界的定义将有助于实现这一目标。
