Characteristic Electroencephalogram of General Anesthesia

Analysis of the Characteristic Electroencephalogram of Patients Undergoing Orthopedic Surgery During the Induction of General Anesthesia and the Unconscious State and Recovery Period With Electroencephalogram Monitoring Device

Patients were enrolled according to predefined inclusion and exclusion criteria. Following surgical admission, standard monitoring was initiated, including continuous assessment of heart rate, blood pressure, electrocardiogram (ECG), and peripheral capillary oxygen saturation (SpO₂). A peripheral intravenous line was established. Bispectral index (BIS) monitoring was performed continuously using a BIS monitor to assess frontal lobe electroencephalographic activity. Based on the type of surgical procedure, regional nerve block was administered. Upon confirmation of adequate block efficacy, patients were assigned to treatment groups according to sealed envelope randomization, and corresponding intravenous sedative regimens were initiated. Sedative induction agents were administered as follows: Group A received remimazolam at 0.08 mg/kg; Group B received dexmedetomidine at 1 μg/kg over 10 minutes; Group C received midazolam at 0.05 mg/kg. Maintenance infusions were as follows: Group A received remimazolam at 1 mg/kg·h; Group B received dexmedetomidine at 0.2-0.7 μg/kg·h; for Group C, if consciousness was not sufficiently suppressed with the initial dose, midazolam was supplemented in increments of 0.01 mg/kg, not exceeding a total dose of 0.1 mg/kg. Following induction, sedation depth was assessed every 2 minutes using the Observer's Assessment of Alertness/Sedation (OAA/S) scale, with auditory stimulation applied every 30 seconds until the patient no longer responded. The time to loss of response to auditory stimuli and the time to loss of consciousness were recorded. Surgical intervention was then performed. Ten minutes prior to anticipated completion of surgery, sedative infusion was discontinued. Sedation depth was reassessed every 2 minutes using the OAA/S scale, with repeated auditory stimulation every 30 seconds to determine the time to return of response and time to recovery of consciousness. If the patient had not achieved an OAA/S score of 5 within 30 minutes after discontinuation of sedation, flumazenil was administered as a reversal agent. Once the OAA/S score reached 5 or spontaneous responses to auditory stimuli were observed-indicating transition back to a responsive state-and complete electroencephalographic data had been collected, no further intervention was required.

Study Overview

• Status: Not yet recruiting
• Conditions: Orthopedic Surgery; EEG Data Analysis
• Intervention / Treatment: Other: After the use of sedative drugs, the changes in the electroencephalogram (EEG) spectrum were observed with an EEG monitor

• Study Type: Observational
• Enrollment (Estimated): 48

Contacts and Locations

• Study Contact: Name: weiliu Zhu, Master; Phone Number: +86 15858287662; Email: zhuweiliu1988@163.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

Patients undergoing elective orthopedic surgery under nerve block combined with intravenous anesthesia

Description

Inclusion Criteria:

• Age: 20 - 60 years old. BMI: 18 ≤ BMI ≤ 24 kg/m2. Right-handed. ASA classification: I - II. Patients scheduled for extremity surgery of upper and lower limbs and undergoing nerve block, those who understand and sign the informed consent form, and those receiving non-endotracheal general anesthesia with remimazolam or dexmedetomidine or midazolam, with Mallampati classification: I - II.

Exclusion Criteria:

• Skin infection at the site of nerve block puncture; history of smoking and alcohol abuse, history of brain surgery, history of cerebral infarction, mental and neurological disorders (MMSE < 18, 3D-CAM positive), history of taking any psychotropic or opioid drugs within 2 weeks, hearing impairment, cardiovascular disease, expected difficulty in airway management or sleep apnea syndrome, drug (including those with a history of allergic reaction to the test drug or contraindications for use) or food allergies, pregnant or lactating patients, patients or family members who refuse to participate, and those who refuse to undergo nerve block.

Study Plan

How is the study designed?

Number of groups / cohorts

3

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
sedation of remimazolam; Electroencephalogram changes under moderate deep sedation induced by remimazolam	Other: After the use of sedative drugs, the changes in the electroencephalogram (EEG) spectrum were observed with an EEG monitor; Electroencephalogram changes under moderate deep sedation
sedation of dexmedetomidine; Electroencephalogram changes under moderate deep sedation induced by dexmedetomidine	Other: After the use of sedative drugs, the changes in the electroencephalogram (EEG) spectrum were observed with an EEG monitor; Electroencephalogram changes under moderate deep sedation
sedation of midazolam; Electroencephalogram changes under moderate deep sedation induced by midazolam	Other: After the use of sedative drugs, the changes in the electroencephalogram (EEG) spectrum were observed with an EEG monitor; Electroencephalogram changes under moderate deep sedation

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Electroencephalogram changes during the perioperative period	Power changes in α and β bands of electroencephalogram during the perioperative period	From the date of random grouping until the end of the surgery

Collaborators and Investigators

• Sponsor: First Affiliated Hospital of Zhejiang University

Publications and helpful links

General Publications

• Schuttler J, Eisenried A, Lerch M, Fechner J, Jeleazcov C, Ihmsen H. Pharmacokinetics and Pharmacodynamics of Remimazolam (CNS 7056) after Continuous Infusion in Healthy Male Volunteers: Part I. Pharmacokinetics and Clinical Pharmacodynamics. Anesthesiology. 2020 Apr;132(4):636-651. doi: 10.1097/ALN.0000000000003103.
• Zhang H, Zhou QQ, Chen H, Hu XQ, Li WG, Bai Y, Han JX, Wang Y, Liang ZH, Chen D, Cong FY, Yan JQ, Li XL. The applied principles of EEG analysis methods in neuroscience and clinical neurology. Mil Med Res. 2023 Dec 19;10(1):67. doi: 10.1186/s40779-023-00502-7.
• Schartner M, Seth A, Noirhomme Q, Boly M, Bruno MA, Laureys S, Barrett A. Complexity of Multi-Dimensional Spontaneous EEG Decreases during Propofol Induced General Anaesthesia. PLoS One. 2015 Aug 7;10(8):e0133532. doi: 10.1371/journal.pone.0133532. eCollection 2015.
• Valizadeh SA, Riener R, Elmer S, Jancke L. Decrypting the electrophysiological individuality of the human brain: Identification of individuals based on resting-state EEG activity. Neuroimage. 2019 Aug 15;197:470-481. doi: 10.1016/j.neuroimage.2019.04.005. Epub 2019 Apr 9.
• White-Dzuro GA, Du A, Brown EN, Akeju O, Peterfreund RA. The Effect of Midazolam Induction on Frontal Electroencephalogram Power. Anesth Analg. 2025 Nov 1;141(5):1185-1187. doi: 10.1213/ANE.0000000000007556. Epub 2025 May 23. No abstract available.

Study record dates

Study Major Dates

• Study Start (Estimated): March 20, 2026
• Primary Completion (Estimated): January 12, 2028
• Study Completion (Estimated): January 12, 2028

Study Registration Dates

• First Submitted: January 8, 2026
• First Submitted That Met QC Criteria: March 9, 2026
• First Posted (Actual): March 12, 2026

Study Record Updates

• Last Update Posted (Actual): March 12, 2026
• Last Update Submitted That Met QC Criteria: March 9, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Other Study ID Numbers: IIT20251166B-R2