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

Bezmialem Vakif University

Status: Completed

Conditions: Interscalene Brachial Plexus Block; Electroencephalogram; Burst Suppression

Treatments: Procedure: General Anesthesia (control group); Procedure: Ultrasound-guided interscalene brachial plexus block (ISB)

Study type: Interventional

Funder types: Other

Identifiers

NCT07081672

Tugba07

Details and patient eligibility

About

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.

Full description

This prospective, randomized, double-blind clinical trial was conducted to evaluate the neurophysiological effects of combining interscalene brachial plexus block (ISB) with general anesthesia in patients undergoing elective shoulder surgery. The primary objective was to investigate how ISB influences intraoperative burst suppression ratio (BSR) and EEG-derived brain activity, using quantitative parameters such as power spectral densities of frequency bands and Patient State Index (PSI).

A total of 50 ASA I-III patients scheduled for shoulder surgery were randomly assigned into two groups: Group B (general anesthesia + ISB) and Group K (general anesthesia only). Standardized general anesthesia was maintained with sevoflurane in both groups. EEG data were recorded continuously using a SedLine® monitor from frontal electrodes (Fp1, Fp2, F7, F8) during four perioperative phases. Spectral analysis was performed using Fast Fourier Transform (FFT) and Welch's method to quantify power in the delta (0.5-4 Hz), theta (4-8 Hz), alpha (8-12 Hz), and beta (13-30 Hz) bands. BSR was calculated based on the duration of EEG suppression epochs, while PSI and SEF (Spectral Edge Frequency) were recorded continuously.

Enrollment: 50 patients

Sex: All

Ages: 18 to 65 years old

Volunteers: No Healthy Volunteers

Inclusion criteria

• 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

Exclusion criteria

• 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

Trial design

Primary purpose: Screening

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: Double Blind

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50 participants in 2 patient groups

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

Active Comparator group

Description:

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.

Treatment:

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 group

Description:

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.

Treatment:

Procedure: General Anesthesia (control group)