監測麻醉深度

Monitoring Depth of Anesthesia

麻醉深度監測儀器是藉腦電圖（electroencephalography, EEG）和額前肌電圖（electromyography, EMG），信號的處理運算成單一指數值，量化為臨床判讀數據，以輔助監測和調節麻醉藥劑量，讓麻醉醫師對於麻醉深度的監控更為客觀。然應用於臨床上，單一的指數往往因為多方因素干擾影響臨床判斷，影響麻醉醫師即時的掌控。因為原始EEG的複雜，使得臨床無法有效地快速判讀，而且也需要較長的學習時間，導致EEG在麻醉上面的應用有限，近年來台灣麻醉開始提倡將原始EEG訊號分析為能量、腦波頻率與時間的頻譜圖：密度譜陣列（density spectrum array, DSA），提供不只單一指數的資訊，更能協助排除潛在干擾，因此在現代倡導精準麻醉的趨勢下，能提早協助臨床判斷可能之問題，更能精準地掌控麻醉的深度，深化為病人量身打造的個人化麻醉。

The application of commercial neuromonitoring devices analyzing intraoperative electroencephalographic (EEG) and electromyographic (EMG) activity from the patient's forehead is introduced to monitor depth of anesthesia and prevent intraoperative accidental awareness. The systems originally calculate a dimensionless index (e.g. from 0-100) using mainly proprietary algorithms, designed to improve clinical titration of anesthetic dose and provide an objective aspect in monitoring sufficient anesthetic depth. Nevertheless, there are multiple cofounding factors limiting the indices' reliability to detect intraoperative awareness and influencing anesthetic strategies. Because of the complexity of raw EEG, intraoperative interpretation of a full-montage EEG requires additional specialized training, which not all anesthesia providers have and limits the anesthetic applications. Currently, we emphasize the importance of processed EEG signals and with the aid of Fourier transformation, the original time domain waveforms of raw EEG is deconstructed into a series of individual sinusoidal waves of different frequencies, amplitudes, and phase, allowing visual digital spectral results in real time, density spectral arrays (DSA). In clinical practice, DSA provides more information than just numeric indices and helps reducing potential interferences and directing anesthetic guidance. Consequently, in the era of precision anesthesia, DSA could improve anesthetic strategies, build up personalized anesthesia and control the anesthetic depth more precisely.