From the Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.
Sleep-Wake-Epilepsy-Center, Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.
Anesth Analg. 2023 Sep 1;137(3):656-664. doi: 10.1213/ANE.0000000000006398. Epub 2023 Mar 24.
Other than clinical observation of a patient's vegetative response to nociception, monitoring the hypnotic component of general anesthesia (GA) and unconsciousness relies on electroencephalography (EEG)-based indices. These indices exclusively based on frontal EEG activity neglect an important observation. One of the main hallmarks of transitions from wakefulness to GA is a shift in alpha oscillations (7.5-12.5 Hz activity) from occipital brain regions toward anterior brain regions ("alpha anteriorization"). Monitoring the degree of this alpha anteriorization may help to guide induction and maintenance of hypnotic depth and prevent intraoperative awareness. However, the occipital region of the brain is completely disregarded and occipital alpha as characteristic of wakefulness and its posterior-to-anterior shift during induction are missed. Here, we propose an application of Narcotrend's reduced power alpha beta (RPAB) index, originally developed to monitor differences in hemispheric perfusion, for determining the ratio of alpha and beta activity in the anterior-posterior axis.
Perioperative EEG data of 32 patients undergoing GA in the ophthalmic surgery department of Bern University Hospital were retrospectively analyzed. EEG was recorded with the Narcotrend® monitor using a frontal (Fp1-Fp2) and a posterior (T9-Oz) bipolar derivation with reference electrode over A2. The RPAB index was computed between both bipolar signals, defining the fronto-occipital RPAB (FO-RPAB). FO-RPAB was analyzed during wakefulness, GA maintenance, and emergence, as well as before and after the intraoperative administration of a ketamine bolus. FO-RPAB was compared with a classical quantitative EEG measure-the spectral edge frequency 95% (SEF-95).
A significant shift of the FO-RPAB was observed during both induction of and emergence from GA ( P < .001). Interestingly, the additional administration of ketamine during GA did not lead to a significant change in FO-RPAB ( P = 0.81). In contrast, a significant increase in the SEF-95 in the frontal channel was observed during the 10-minute period after ketamine administration ( P < .001).
FO-RPAB appears to qualify as a marker of unconsciousness, reflecting physiological fronto-occipital activity differences during GA. In contrast to frontal SEF-95, it is not disturbed by additional administration of ketamine for analgesia.
除了对患者对伤害性刺激的植物状态反应进行临床观察之外，监测全身麻醉（GA）和意识丧失的催眠成分依赖于基于脑电图（EEG）的指标。这些完全基于额部 EEG 活动的指标忽略了一个重要的观察结果。从清醒到 GA 的转变的主要特征之一是从枕部脑区向额部脑区转移的 alpha 振荡（7.5-12.5 Hz 活动）（“alpha 前移”）。监测这种 alpha 前移的程度可能有助于指导催眠深度的诱导和维持，并防止术中意识。然而，大脑的枕部区域完全被忽视了，并且忽略了觉醒时的枕部 alpha 及其在诱导过程中的从前向后转移。在这里，我们提出了 Narcotrend 的减少功率 alpha beta（RPAB）指数的应用，该指数最初是为了监测半球灌注的差异而开发的，用于确定前后轴上 alpha 和 beta 活动的比率。
回顾性分析了在伯尔尼大学医院眼科手术部接受 GA 的 32 名患者的围手术期 EEG 数据。使用 Narcotrend®监视器通过额部（Fp1-Fp2）和枕部（T9-Oz）双极记录进行 EEG 记录，参考电极置于 A2 上。在两个双极信号之间计算 RPAB 指数，定义为额枕 RPAB（FO-RPAB）。在清醒、GA 维持和苏醒期间以及术中给予氯胺酮推注前后分析 FO-RPAB。将 FO-RPAB 与经典的定量 EEG 测量指标-频谱边缘频率 95%（SEF-95）进行比较。
在 GA 的诱导和苏醒过程中均观察到 FO-RPAB 的明显移位（P <.001）。有趣的是，在 GA 期间额外给予氯胺酮并没有导致 FO-RPAB 发生显著变化（P = 0.81）。相反，在给予氯胺酮后的 10 分钟内，在前额通道中观察到 SEF-95 显著增加（P <.001）。
FO-RPAB 似乎可作为无意识的标志物，反映 GA 期间的生理额枕部活动差异。与额部 SEF-95 不同，它不受额外给予氯胺酮进行镇痛的干扰。
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