Electroencephalographic Trajectories During Emergence From Inhalational and Total Intravenous Anesthesia

• No Intervention: Observational Cohort (Other): No Intervention: Observational Cohort

Primary outcomes

• EEG trajectories during emergence from anesthesia [From discontinuation of the anesthetic maintenance drugs until 30 minutes after tracheal extubation.]: 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.

Secondary outcomes

• EEG spectral power characteristics [From discontinuation of the anesthetic maintenance drugs until 30 minutes after tracheal extubation]: 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 [From discontinuation of the anesthetic maintenance drugs until 30 minutes after tracheal extubation]: 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 [From discontinuation of the anesthetic maintenance drugs until 30 minutes after tracheal extubation]: 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 [From discontinuation of the anesthetic maintenance drugs until 30 minutes after tracheal extubation]: 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.
• Length of stay in the postanesthesia care unit [From discontinuation of the anesthetic maintenance drugs until 30 minutes after tracheal extubation]: Duration from admission to discharge from the postanesthesia care unit.
• Aldrete score at PACU discharge [Before discharge from the postanesthesia care unit.]: Recovery status will be assessed using the Aldrete score at discharge from the postanesthesia care unit.
• Richmond Agitation-Sedation Scale score at PACU discharge [From discontinuation of the anesthetic maintenance drugs until 30 minutes after tracheal extubation]: Level of agitation and sedation will be assessed using the Richmond Agitation-Sedation Scale (RASS) at PACU discharge.
• Pain intensity measured using the Numeric Rating Scale at PACU discharge [From discontinuation of the anesthetic maintenance drugs until 30 minutes after tracheal extubation]: Pain intensity will be assessed using the 0-10 Numeric Rating Scale (NRS) at PACU discharge, with higher scores indicating greater pain intensity.

Sex: All, ages: 18 Years to 60 Years, accepts healthy volunteers

Inclusion criteria

1. Adults aged 18-60 years.
2. Patients classified as American Society of Anesthesiologists (ASA) physical status I-III.
3. Patients scheduled to undergo elective non-cardiac and non-neurosurgical surgery under general anesthesia.
4. Expected duration of surgery ≥60 minutes.
5. Expected intraoperative maintenance anesthesia with either total intravenous anesthesia (TIVA) or inhalational anesthesia .
6. Patients who understand the study procedures and voluntarily provide written informed consent.

Exclusion Criteria

1. History of central nervous system disorders, including epilepsy, Parkinson's disease, dementia, previous stroke with residual neurological deficits, or other clinically significant neurological diseases.
2. Long-term use (≥4 weeks) of sedative-hypnotic drugs, antidepressants, antipsychotic medications, or other medications that may significantly affect central nervous system function.
3. Pre-existing cognitive impairment or severe visual/hearing impairment preventing assessment of recovery of consciousness.
4. Skin lesions, trauma, or other conditions affecting placement of frontal EEG electrodes.
5. Emergency surgery, neurosurgery, cardiac surgery, planned deep sedation with postoperative intubation, or direct transfer to the intensive care unit after surgery.
6. Severe intraoperative adverse events, including cardiac arrest, malignant hyperthermia, severe allergic reactions, major bleeding, or situations requiring substantial changes in the planned anesthesia maintenance strategy.
7. Body mass index (BMI) ≥30 kg/m² or ≤18 kg/m².
8. Refusal to participate or withdrawal of informed consent during the study.1. Adults aged 18-60 years, with no restriction on sex.