探討麻醉深度與術中意識殘留之神經機轉

Exploring Depth of Anesthesia and Intraoperative Consciousness Residue through Neurophysiological Mechanisms

在全身麻醉臨床實務中，如何在維持病人無痛、無意識的同時，避免過深麻醉所造成的術後認知障礙，始終是一項挑戰。近年來，腦電圖（electroencephalogram, EEG）被廣泛應用於評估麻醉深度與意識狀態，但其與記憶形成之關聯性仍未完全釐清。研究指出，即使在無反應的麻醉狀態下，大腦仍可能處於可進行感知與注意力處理的階段，進而形成潛在記憶。事件相關電位（ERP）如N1與P3反映了知覺與注意力的不同層面，後者尤其易受麻醉劑量影響。指標如α波前額化（anteriorization）、慢波飽和度（slow wave activity saturation, SWAS）、相位振幅耦合（PmaxI），以及認知努力指數（cognitive effort index, CEI），皆為評估意識層次的重要工具，惟現行監測系統如BIS與Sedline仍無法即時辨識注意力波動。本文整理當前文獻，從神經生理機轉出發，探討EEG在麻醉意識監測與術後記憶保留上的臨床意涵。

In clinical general anesthesia practice, achieving sufficient unconsciousness and analgesia while avoiding excessive depth that may lead to postoperative cognitive dysfunction remains a challenge. Electroencephalography (EEG) has become a key tool in monitoring anesthetic depth and states of consciousness, yet its relationship with memory formation remains elusive. Emerging evidence suggests that even during unresponsive states under anesthesia, the brain may still process sensory input and attention, potentially forming implicit memories. Event-related potentials (ERPs) such as N1 and P3 reflect perceptual and attentional processes respectively, with P3 being more sensitive to anesthetic suppression. EEG markers including alpha anteriorization, slow wave activity saturation (SWAS), phase-amplitude coupling indices (PmaxI), and the Cognitive Effort Index (CEI) provide insights into levels of consciousness, though clinical monitors like BIS and Sedline are limited in detecting real-time attentional fluctuations. This review integrates current literature and electrophysiological principles to examine how EEG-based metrics relate to anesthesia depth, attention, and memory, with implications for optimizing patient safety and minimizing cognitive side effects postoperatively.