BACKGROUND Near-infrared spectroscopy (NIRS) has been utilized widely in anesthesia and intensive care to monitor regional cerebral oxygen saturation (rScO2). A normal oxygenation of extracerebral tissues may overlay and thereby mask cerebral desaturations, a phenomenon known as extracerebral contamination. We investigated the effect of a cessation of extracerebral tissue perfusion on rScO2 in patients with anoxic brains. METHODS In a single-center, prospective, observational study, brain dead adults undergoing organ donation were investigated. rScO2 was measured bifrontally using the INVOS 5100c/7100 as well as the ForeSight Elite system. To achieve an efficient conservation of organs and to prevent a redistribution of the perfusion fluid to other tissues, the aorta was clamped prior to organ perfusion. rScO2 was monitored until at least forty minutes after aortic clamping. The primary outcome was the amount of extracerebral contamination as quantified by the absolute decrease in rScO2 after aortic clamping. Secondary outcomes were the absolute rScO2-values obtained before and after clamping. RESULTS Twelve organ donors were included. Aortic clamping resulted in a significantly (p<0.001) greater absolute decrease in rScO2 when comparing the INVOS (43.0 ± 9.5%) to the ForeSight (27.8 ± 7.1%) monitor. Before aortic clamping, near normal rScO2-values were obtained by the INVOS (63.8 ± 6.2%) and the ForeSight-monitor (67.7 ± 6 .5%). The rScO2 significantly (p<0.001) dropped to 20.8 ± 7.8% (INVOS) and 39.9 ± 8.1% (ForeSight) thirty minutes after clamping, i.e. a condition of a desaturation of both extracerebral and cerebral tissues. CONCLUSIONS The abrupt end of extracerebral contamination, caused by aortic clamping, affected both NIRS monitors to a considerable extent. Both the INVOS and the ForeSight-monitor were unable to detect severe cerebral hypoxia/anoxia under conditions of normal extracerebral oxygenation. While both NIRS-monitors may guide measures to optimize arterial oxygen supply to the head, they should not be used with the intention to detect isolated cerebral desaturations.

中文翻译：

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器官捐献过程中揭示的脑外污染对近红外光谱的影响：脑死亡器官捐献者的一项前瞻性观察研究。

背景技术近红外光谱（NIRS）已广泛应用于麻醉和重症监护中以监测局部脑氧饱和度（rScO2）。脑外组织的正常氧合可能会叠加并从而掩盖脑饱和度降低，这种现象称为脑外污染。我们研究了停止脑外组织灌注对缺氧脑患者 rScO2 的影响。方法 在一项单中心、前瞻性、观察性研究中，对接受器官捐献的脑死亡成年人进行了调查。使用 INVOS 5100c/7100 以及 ForeSight Elite 系统对 rScO2 进行双额测量。为了实现器官的有效保存并防止灌注液重新分配到其他组织，在器官灌注之前夹住主动脉。监测 rScO2 直至主动脉夹闭后至少四十分钟。主要结果是脑外污染量，通过主动脉夹闭后 rScO2 绝对下降来量化。次要结果是钳夹前后获得的绝对 rScO2 值。结果 十二名器官捐献者被纳入其中。与 INVOS (43.0 ± 9.5%) 与 ForeSight (27.8 ± 7.1%) 监测仪相比，主动脉夹闭导致 rScO2 绝对值显着降低 (p<0.001)。在主动脉夹闭之前，INVOS (63.8 ± 6.2%) 和 ForeSight 监测仪 (67.7 ± 6 .5%) 获得接近正常的 rScO2 值。夹闭后三十分钟，rScO2 显着（p<0.001）降至20.8±7.8%（INVOS）和39.9±8.1%（ForeSight），即脑外组织和脑组织均去饱和的情况。结论 主动脉夹闭引起的脑外污染突然结束，在相当大程度上影响了两台 NIRS 监测仪。在正常脑外氧合条件下，INVOS 和 ForeSight 监测仪均无法检测到严重的脑缺氧/缺氧。虽然这两种 NIRS 监测仪可以指导优化头部动脉供氧的措施，但它们不应用于检测孤立的脑饱和度降低。