General anesthesia emergence is a critical transition during which patients recover from an anesthetic-induced unconscious state to consciousness. This period is associated with various early postoperative complications, including emergence agitation, postoperative nausea and vomiting, delayed recovery, and impaired recovery quality in the Post-Anesthesia Care Unit (PACU). Although total intravenous anesthesia (TIVA) and inhalational anesthesia (IA) are widely used maintenance strategies, differences in their effects on cerebral recovery patterns during emergence remain incompletely understood.
Conventional assessments of emergence, such as time to eye opening, extubation time, and clinical sedation assessments, mainly reflect behavioral recovery and cannot directly characterize the dynamic process of cerebral functional recovery. Electroencephalography (EEG) provides continuous and non-invasive measurement of cortical activity and may enable objective characterization of anesthetic emergence.
Previous studies suggest that emergence from anesthesia involves dynamic transitions among distinct EEG states rather than a simple reversal of anesthetic induction, and specific EEG trajectories may be associated with abnormal emergence and PACU delirium. Therefore, this single-center prospective observational cohort study aims to continuously collect emergence-phase EEG data from patients receiving TIVA or IA without altering clinical anesthesia management. The study will compare EEG trajectory characteristics, spectral features, and aperiodic parameters between different anesthesia maintenance modalities and explore their associations with emergence quality and early postoperative complications.
This study may provide further insights into neurophysiological patterns of anesthetic emergence and support future optimization of emergence monitoring and perioperative management.
Adults aged 18-60 years.
Patients classified as American Society of Anesthesiologists (ASA) physical status I-III.
Patients scheduled to undergo elective non-cardiac and non-neurosurgical surgery under general anesthesia.
Expected duration of surgery ≥60 minutes.
History of central nervous system disorders, including epilepsy, Parkinson's disease, dementia, previous stroke with residual neurological deficits, or other clinically significant neurological diseases.
Long-term use (≥4 weeks) of sedative-hypnotic drugs, antidepressants, antipsychotic medications, or other medications that may significantly affect central nervous system function.
Pre-existing cognitive impairment or severe visual/hearing impairment preventing assessment of recovery of consciousness.
Skin lesions, trauma, or other conditions affecting placement of frontal EEG electrodes.
This study will enroll adult patients aged 18-60 years who are scheduled to undergo elective non-cardiac and non-neurosurgical surgery under general anesthesia. Participants will receive routine clinical anesthesia management, and the choice of total intravenous anesthesia or inhalational anesthesia will be determined by the attending anesthesiologist according to clinical practice.
Cohort
Prospective
No Intervention: Observational Cohort
Other interventionNo Intervention: Observational Cohort
EEG trajectories during emergence from anesthesia
Frontal EEG recordings will be analyzed to characterize spectral activity and its temporal evolution during emergence from general anesthesia. Prespecified EEG parameters will include delta-band spectral power and alpha/spindle-band spectral power derived from power spectral density estimates. These spectral features will be used to characterize EEG states and transitions during emergence, including state occupancy, transition timing, and transition sequences.
EEG spectral power characteristics
Frontal EEG recordings will be obtained during emergence from general anesthesia. The EEG will be segmented into consecutive prespecified epochs, and spectral analysis will be performed for each segment. Power spectral density will be calculated within the following frequency bands: delta, 0.5-4 Hz; theta, 4-8 Hz; alpha/spindle, 8-13 Hz; beta, 13-30 Hz; and gamma, 30-45 Hz. Absolute power and relative power will be calculated for each frequency band. Relative power will be defined as the power within each frequency band divided by the total spectral power across the prespecified analysis frequency range. The alpha-to-delta power ratio, alpha peak frequency, and alpha peak power will also be calculated. Gamma-band findings will be considered exploratory because of possible electromyographic contamination.
Aperiodic exponent of the EEG power spectrum
The aperiodic exponent will be estimated from frontal EEG power spectra using a prespecified spectral parameterization method that separates periodic spectral peaks from the aperiodic 1/f-like background.
Aperiodic offset of the EEG power spectrum
The aperiodic offset will be estimated from frontal EEG power spectra using a prespecified spectral parameterization method that separates periodic spectral peaks from the aperiodic 1/f-like background.
Auxiliary EEG and monitor-derived parameters during emergence
Additional EEG-derived and monitor-generated parameters will be assessed during emergence from general anesthesia. Spectral edge frequency 90% (SEF90) will be calculated as the frequency below which 90% of the total EEG spectral power within the prespecified analysis frequency range is contained. In addition, the Ai Index and electromyographic (EMG) index generated by the EEG monitoring system will be recorded continuously during emergence.
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