• K Hayashi, K Indo, and T Sawa.
• Department of Anesthesiology, Kyoto Chubu Medical Center, Yagi, Ueno 25, Nantan City, Kyoto, Japan; Medical Education and Research Center, Meiji University of Integrative Medicine, Kyoto, Japan. Electronic address: zukko@koto.kpu-m.ac.jp.
• Clin Neurophysiol. 2020 Sep 1; 131 (9): 2150-2157.

ObjectiveAlthough the characteristics of electroencephalograms (EEGs) have been reported to change with age, anaesthesia-dependent oscillatory features and reactivity of the super-elderly EEG to anaesthesia have not been examined in detail.MethodsParticipants comprised 20 super-elderly patients (age; mean ± standard deviation, 87.1 ± 3.8 years) and 20 young adult patients (35.5 ± 8.5 years). At three levels of sevoflurane anaesthesia (minimum alveolar concentration [MAC] of 0.3, 0.7, and 1.4), oscillatory features of the frontal EEG were examined by analysing quadratic phase coupling (bicoherence) and power spectrum in α and δ-θ areas and compared in an anaesthesia-dependent manner, using the Friedman test.ResultsAmong super-elderly individuals, bicoherences in the δ-θ area showed anaesthesia-dependent increases (median [interquartile range], 12.9% [5.2%], 19.2% [9.1%], 23.3% [8.7%]; 0.3, 0.7, 1.4 MAC sevoflurane, p = 0.000), whereas bicoherence in the α area did not change at these different anaesthesia levels (11.2% [3.9%], 12.5% [4.4%], 14.1% [5.7%], respectively; p = 0.142), counter to the results found in young adult patients, where both δ-θ and α bicoherences changed with anaesthesia.ConclusionsIn the super-elderly, δ-θ bicoherence of EEG shows anaesthesia- dependent changes, whereas α activity remains small irrespective of anaesthesia level.SignificanceQuantification of δ-θ bicoherence is a candidate for anaesthesia monitoring in the super-elderly.Copyright © 2020 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

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