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. 2023 Jul 31;13(8):1149.
doi: 10.3390/brainsci13081149.

Differences in the EEG Power Spectrum and Cross-Frequency Coupling Patterns between Young and Elderly Patients during Sevoflurane Anesthesia

Xinxin Zhang  1 , Ao Li  1   2 , Sa Wang  1 , Tingting Wang  1 , Tiantian Liu  1 , Yonghui Wang  1 , Jingwen Fu  1 , Guangchao Zhao  1 , Qianzi Yang  1   3 , Hailong Dong  1
Affiliations

Differences in the EEG Power Spectrum and Cross-Frequency Coupling Patterns between Young and Elderly Patients during Sevoflurane Anesthesia

Xinxin Zhang et al. Brain Sci. .

Abstract

Electroencephalography (EEG) is widely used for monitoring the depth of anesthesia in surgical patients. Distinguishing age-related EEG features under general anesthesia will help to optimize anesthetic depth monitoring during surgery for elderly patients. This retrospective cohort study included 41 patients aged from 18 to 79 years undergoing noncardiac surgery under general anesthesia. We compared the power spectral signatures and phase-amplitude coupling patterns of the young and elderly groups under baseline and surgical anesthetic depth. General anesthesia by sevoflurane significantly increased the spectral power of delta, theta, alpha, and beta bands and strengthened the cross-frequency coupling both in young and elderly patients. However, the variation in EEG power spectral density and the modulation of alpha amplitudes on delta phases was relatively weaker in elderly patients. In conclusion, the EEG under general anesthesia using sevoflurane exhibited similar dynamic features between young and elderly patients, and the weakened alteration of spectral power and cross-frequency coupling patterns could be utilized to precisely quantify the depth of anesthesia in elderly patients.

Keywords: EEG monitoring; aging brain; general anesthesia.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Dynamic EEG changes in both young and elderly patients during the baseline and maintenance period: (A) The group median spectrogram of elderly patients and young patients during the baseline; (B) Spectral analysis of young patients (orange line, median; shaded area, 25th–75th percentile) and elderly patients (blue line, median; shaded area, 25th–75th percentile) during the baseline; (C) The group median spectrogram of elderly patients and young patients during general anesthesia; (D) Spectral analysis of young patients (orange line, median; shaded area, 25th–75th percentile) and elderly patients (blue line, median; shaded area, 25th–75th percentile) during general anesthesia; (E–L) Change in the total power, delta, theta, alpha, beta, gamma, edge, and alpha peak frequency in elderly and young patients in the wake vs. anesthesia maintenance period. Statistical significance is indicated as * Padj < 0.05, ** Padj < 0.01, and *** Padj < 0.001.
Figure 2
Figure 2
Phase–amplitude coupling patterns of young and elderly patients during the wake state: (A,B) Prefrontal comodulograms demonstrated that low-frequency oscillations were no driver of higher frequencies during wake states; (C,D) Prefrontal phaseampograms demonstrated the relative amplitude of higher frequencies was uniformly distribution; (E,F) Prefrontal circular phasor plots demonstrated that the resultant vector length was closer to 0; (G,H) Mean amplitude distribution was uniformly distributed during wake states.
Figure 3
Figure 3
Distinct phase–amplitude coupling patterns of young and elderly patients during the maintenance period: (A,B) Prefrontal comodulograms demonstrated that delta oscillations modulated higher frequencies during sevoflurane-induced anesthetic states for both patient groups; (C,D) Prefrontal phaseampograms between delta and higher frequencies demonstrated that ‘peak-max’ patterns of phase-limited neural activity are associated anesthetic states; (E,F) Prefrontal circular phasor plots demonstrated that neural activity distributed around the 0 phase of delta oscillations, but the resultant vector length of elderly patients was smaller than in young patients; (G,H) Mean amplitude distribution was not uniformly distributed during sevoflurane-induced anesthetic states.
Figure 4
Figure 4
(A) the MI of the delta phase to alpha amplitudes in both young and elderly patients (B) the MI of the delta phase to beta amplitudes in both young and elderly patients. Change in MI values in elderly and young patients in the wake vs. anesthesia maintenance period. Statistical significance is indicated as ** Padj < 0.01, and *** Padj < 0.001.
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