Burst Suppression, Electroencephalogram, Interscalene Brachial Plexus Block
Conditions
Keywords
burst supression, electroencephalogram, interscalene brachial plexus block, general anesthesia
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.
Detailed 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.
Interventions
PROCEDUREUltrasound-guided interscalene brachial plexus block (ISB)
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.
PROCEDUREGeneral Anesthesia (control group)
General anesthesia without regional block
Sponsors
Bezmialem Vakif University
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
SCREENING
Masking
DOUBLE (Subject, Outcomes Assessor)
Masking description
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.
Eligibility
Sex/Gender
ALL
Age
18 Years to 65 Years
Healthy volunteers
No
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Burst Suppression Ratio (BSR) | peroperative | 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). |
| Power Spectral Density (PSD) Analysis | peroperative | 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. |
| Patient State Index (PSI) | peroperative | 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. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Nursing Delirium Screening Scale (NUDESC) | During PACU stay (up to 2 hours) | The Nursing Delirium Screening Scale (NU-DESC) is a validated, nurse-administered tool used to detect signs of postoperative delirium. It assesses five domains: disorientation, inappropriate behavior, inappropriate communication, illusions/hallucinations, and psychomotor retardation. Each domain is scored from 0 to 2, resulting in a total score ranging from 0 to 10. A total score of ≥2 indicates a high probability of delirium. In this study, NU-DESC scores were recorded during the early postoperative period to identify any acute cognitive changes. |
| Mean Arterial Pressure (MAP) | peroperative | Intraoperative mean arterial pressure (MAP) was continuously monitored and recorded at predefined intervals throughout the procedure. Particular attention was paid to measurements taken during anesthesia induction, surgical positioning in the beach chair position, and skin incision. These data were analyzed to evaluate hemodynamic stability and to investigate the potential sympatholytic effects of the interscalene brachial plexus block (ISB). |
| Oxygen Saturation (SpO₂) | peroperative | Peripheral oxygen saturation (SpO₂) was monitored continuously during surgery and recorded at predetermined intervals. Measurements during critical phases, including induction, positioning, and incision, were evaluated to ensure adequate oxygenation and assess any indirect effects of ISB on respiratory function. |
| Heart Rate (HR) | peroperative | Heart rate (HR) was continuously monitored intraoperatively and recorded at specified time points, with focused analysis during key phases such as anesthesia induction, patient positioning (beach chair position), and surgical incision. Group comparisons were made to assess ISB-associated modulation of cardiac autonomic response. |
| Anesthetic and Analgesic Drug Consumption | peroperative | Total doses of intraoperative sevoflurane, remifentanil, and propofol were recorded for each patient. Volatile anesthetic consumption was quantified in minimum alveolar concentration-hours (MAC-h). The aim was to evaluate whether ISB reduced the requirement for hypnotic and opioid agents during surgery. |
| Postoperative Pain Scores | During PACU stay (up to 2 hours) | Postoperative pain intensity was assessed using the Numerical Rating Scale (NRS), which ranges from 0 (no pain) to 10 (worst imaginable pain). Higher scores indicate greater pain severity. Pain scores were recorded during the post-anesthesia care unit (PACU) stay, specifically within the first two hours following surgery, to evaluate early postoperative analgesia. |
Countries
Turkey (Türkiye)
Outcome results
None listed