Impact of Interscalene Block Combined With General Anesthesia on Burst Suppression in Shoulder Surgery Patients

NCT07081672 | Completed

• 1 other identifier: Tugba07
• Study Type: interventional
• Target: 50
• Locations: 1 country
• Sites: 1

Brief Summary

This prospective, randomized, double-blind clinical study aimed to investigate the effects of combining general anesthesia with an interscalene brachial plexus block (ISB) on burst suppression ratio (BSR) and electroencephalographic (EEG) activity in patients undergoing elective shoulder surgery. A total of 50 patients were allocated into two groups: those receiving general anesthesia with ISB (Group B) and those receiving general anesthesia alone (Group K). Intraoperative EEG recordings were obtained from frontal electrodes (Fp1, Fp2, F7, F8) using a SedLine® monitor. Power spectral analysis was conducted for delta, theta, alpha, and beta frequency bands, alongside assessment of Patient State Index (PSI) and BSR.

Conditions

Burst Suppression; Electroencephalogram; Interscalene Brachial Plexus Block

Keywords

burst supression; electroencephalogram; interscalene brachial plexus block; general anesthesia

Outcome Measures

Primary Outcomes (3)

• Burst Suppression Ratio (BSR)

  Burst Suppression Ratio (BSR): The main quantitative indicator of deep cortical suppression, calculated as the percentage of time the EEG signal remained in a suppression state (defined as amplitude \<±10 μV for ≥0.5 seconds) during surgery. BSR was recorded continuously and analyzed across four perioperative phases (Phase 0-3).

  peroperative

• Power Spectral Density (PSD) Analysis

  The average spectral power (μV²) of EEG signals was analyzed for four conventional frequency bands-delta (0.5-4 Hz), theta (4-8 Hz), alpha (8-12 Hz), and beta (13-30 Hz)-using FFT-based spectral analysis. These values were calculated from frontal electrodes (Fp1, Fp2, F7, F8), and comparisons were made between Group B (ISB group) and Group K (control group) at each phase.

  peroperative

• Patient State Index (PSI)

  The Patient State Index (PSI), a proprietary quantitative measure ranging from 0 to 100, is derived from multichannel electroencephalogram (EEG) signals using the SedLine® brain function monitoring system. Higher PSI values indicate lighter levels of anesthesia or increased cortical activity, whereas lower values correspond to deeper anesthetic states. In this study, PSI values were utilized to monitor the level of consciousness and cortical stability during the intraoperative period. Particular emphasis was placed on PSI trends observed during Phase 1 (following the administration of the interscalene block but prior to the induction of general anesthesia), in order to investigate any pre-anesthetic central nervous system effects attributable to the regional block.

  peroperative

Secondary Outcomes (6)

• Mean Arterial Pressure (MAP)

  peroperative

• Anesthetic and Analgesic Drug Consumption

  peroperative

• Postoperative Pain Scores

  During PACU stay (up to 2 hours)

• Nursing Delirium Screening Scale (NUDESC)

  During PACU stay (up to 2 hours)

• Heart Rate (HR)

  peroperative

Study Arms (2)

Patients in Group B received an ultrasound-guided interscalene brachial plexus block (ISB)

ACTIVE COMPARATOR

A total of 20 mL of 0.125% bupivacaine was administered around the C5-C6 nerve roots under real-time ultrasound visualization. Fifteen minutes after the block, both sensory and motor block assessments were performed to confirm effectiveness. Following confirmation of a successful block, a standardized general anesthesia protocol was initiated using 1-2 mg/kg propofol, 1 mcg/kg fentanyl, and 0.6 mg/kg rocuronium, followed by endotracheal intubation. Anesthesia was maintained with sevoflurane (1.0-1.3 MAC), and depth of anesthesia was continuously monitored using the SedLine® EEG monitor.

Procedure: Ultrasound-guided interscalene brachial plexus block (ISB)

Patients in Group K did not receive any regional anesthesia prior to general anesthesia induction.

ACTIVE COMPARATOR

After standard monitoring was established, including ECG, non-invasive blood pressure, SpO₂, and SedLine® EEG monitoring, a 5-minute baseline EEG recording (Phase 0) was obtained with the patient at rest, eyes closed, and in a noise-minimized environment. Subsequently, general anesthesia was induced using 1-2 mg/kg propofol, 1 mcg/kg fentanyl, and 0.6 mg/kg rocuronium, followed by endotracheal intubation. Anesthesia was maintained with sevoflurane at 1.0-1.3 MAC in a mixture of 50% oxygen and air. To ensure adequate intraoperative analgesia, a remifentanil infusion (0.05-0.2 μg/kg/min) was administered and titrated according to Surgical Pleth Index (SPI) values, aiming to maintain SPI between 20-50.

Procedure: General Anesthesia (control group)

Interventions

Ultrasound-guided interscalene brachial plexus block (ISB) PROCEDURE

The intervention consisted of an ultrasound-guided interscalene brachial plexus block (ISB) administered to patients in Group B prior to general anesthesia. The block was performed using a posterior in-plane approach with real-time ultrasound visualization. A total of 20 mL of 0.125% bupivacaine was injected around the C5-C6 nerve roots under sterile conditions by experienced anesthesiologists.

Patients in Group B received an ultrasound-guided interscalene brachial plexus block (ISB)

General Anesthesia (control group) PROCEDURE

General anesthesia without regional block

Patients in Group K did not receive any regional anesthesia prior to general anesthesia induction.

Eligibility Criteria

• Age: 18 Years - 65 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Patients classified as ASA Physical Status I-III
• Aged between 18 and 65 years
• Scheduled for elective shoulder surgery under general anesthesia, with or without interscalene brachial plexus block

You may not qualify if:

• Advanced renal failure
• Advanced hepatic failure
• Body mass index (BMI) \> 40 kg/m²
• History of central nervous system disorders
• Diagnosed psychiatric illness
• History of substance abuse
• Known allergy to any of the drugs used in the study
• Refusal to participate or to provide informed consent
• Termination Criteria:
• Severe hypotension (mean arterial pressure \< 50 mmHg despite treatment)
• Severe bradycardia (heart rate \< 40 bpm requiring intervention)
• Profound hypoxia (SpO₂ \< 90% despite oxygen support)
• Drug-related allergic reactions

Sponsors & Collaborators

• Bezmialem Vakif University: lead

Study Sites (1)

Bezmialem Vakif University

Istanbul, Fatih, 34093, Turkey (Türkiye)

Location

MeSH Terms

Interventions

Anesthesia, General; Control Groups

Intervention Hierarchy (Ancestors)

Anesthesia; Anesthesia and Analgesia; Epidemiologic Research Design; Epidemiologic Methods; Investigative Techniques; Research Design; Methods

Study Officials

• Kazım Karaaslan, MD

  Bezmialem Vakif University

  STUDY DIRECTOR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: DOUBLE
• Who Masked: PARTICIPANT, OUTCOMES ASSESSOR
• Masking Details: The study was conducted in a double-blind design: both the patients and the professional responsible for EEG data analysis were blinded to group allocation.
• Purpose: SCREENING
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: MD

Study Record Dates

• First Submitted: July 2, 2025
• First Posted: July 23, 2025
• Study Start: January 29, 2025
• Primary Completion: July 15, 2025
• Study Completion: July 20, 2025
• Last Updated: July 30, 2025

Record last verified: 2025-07

Data Sharing

• IPD Sharing: Will not share

Locations

TU (1)