Cerebral Desaturation Burden After Interscalene or Suprascapular-Axillary Block for Shoulder Arthroscopy

Comparison of the Effects of Preoperative Interscalene Block and Combined Suprascapular and Axillary Nerve Blocks on Cerebral Desaturation Burden in Patients Undergoing Elective Shoulder Arthroscopy in the Beach-Chair Position Under General Anesthesia: A Prospective Randomized Study

Shoulder arthroscopy is often performed with the patient in an upright beach-chair position. Changes in position and anesthesia may affect blood pressure and oxygen delivery to the brain. This study compares two ultrasound-guided nerve block approaches performed before general anesthesia: interscalene block and combined suprascapular and axillary nerve blocks. Participants will be randomly assigned to one of these approaches. Both groups will receive the same general anesthetic and 20 mL of 0.25% bupivacaine for the assigned block approach. Cerebral oxygen saturation will be monitored continuously using sensors placed on the forehead. The main outcome is the total cerebral desaturation burden, measured as the area below 80% of each participant's baseline cerebral oxygen saturation during monitoring. Other outcomes include the occurrence and duration of desaturation, minimum cerebral oxygen saturation, blood pressure and heart rate events, vasopressor use, and immediate recovery and a Mini-Mental State Examination to assess cognitive functions.

Study Overview

• Status: Recruiting
• Conditions: Cerebral Oxygenation During Shoulder Arthroscopy
• Intervention / Treatment: Procedure: Ultrasound-Guided Interscalene Nerve Block; Procedure: ltrasound-Guided Combined Suprascapular and Axillary Nerve Blocks

• Study Type: Interventional
• Enrollment (Estimated): 60
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Muhammed Enes Aydin, Associate Professor; Phone Number: +905543318289; Email: enesmd@msn.com
• Study Contact Backup: Name: Emir Sahan, assistant doctor; Phone Number: +905332773733; Email: Emirsahan94@gmail.com

Study Locations

• Turkey (Türkiye)
  • Erzurum, Turkey (Türkiye), 25000
    • Recruiting
    • Ataturk University
    • Contact: Muhammed Enes Aydin, principal investigator; Phone Number: 05543318289; Email: enesmd@msn.com
    • Contact: Emir Sahan, assistant doctor; Phone Number: +90-533-277-37-33; Email: Emirsahan94@gmail.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 65 years (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Age 18-65 years
• ASA physical status I or II
• Scheduled for elective shoulder arthroscopy under general anesthesia in the beach-chair position
• Provides written informed consent

Exclusion Criteria:

• Allergy to local anesthetics
• Previous cervical spine surgery
• History of cerebrovascular disease or carotid artery surgery
• Serious cardiac disease, including advanced heart failure or significant valvular disease
• Neurological disease, including epilepsy, multiple sclerosis, or Parkinson's disease
• Dementia or cognitive impairment
• Coagulopathy or contraindication to peripheral nerve block due to anticoagulant use
• Pregnancy
• Body mass index greater than 35 kg/m²
• Technical or anatomical obstacle to performing the planned nerve block

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Interscalene Block (ISB); Participants will receive a preoperative ultrasound-guided interscalene nerve block using 20 mL of 0.25% bupivacaine.	Procedure: Ultrasound-Guided Interscalene Nerve Block; A preoperative ultrasound-guided interscalene block will be performed with the patient supine and the head turned to the opposite side. A total of 20 mL of 0.25% bupivacaine will be injected around the brachial plexus roots.
Experimental: Combined Suprascapular and Axillary Nerve Blocks (SSAX); Participants will receive preoperative ultrasound-guided suprascapular and axillary nerve blocks. A total of 20 mL of 0.25% bupivacaine will be divided between the two blocks.	Procedure: ltrasound-Guided Combined Suprascapular and Axillary Nerve Blocks; Preoperative ultrasound-guided suprascapular and axillary nerve blocks will be performed. A total of 20 mL of 0.25% bupivacaine will be divided between the two block sites.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Total Cerebral Desaturation Burden (AUC)	The area under the curve below the desaturation threshold, defined as 80% of baseline regional cerebral oxygen saturation (rSO₂). AUC will be calculated separately for each hemisphere; the mean of the two hemispheres will be used for the primary comparison. Only desaturation episodes lasting at least 15 seconds will be included. The unit is %·min.	From baseline measurement before the nerve block until 10 minutes after return to the supine position.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incidence and Number of Cerebral Desaturation Events	Proportion of participants with, and number of, cerebral desaturation events, defined as a decrease in rSO₂ of at least 20% from baseline lasting at least 15 seconds.	From baseline measurement before the nerve block until 10 minutes after return to the supine position.
Total Time Below the Cerebral Desaturation Threshold	Total time during which rSO₂ remains below 80% of baseline.	From baseline measurement before the nerve block until 10 minutes after return to the supine position.
Minimum Right and Left Cerebral rSO₂	Minimum rSO₂ values recorded from the right and left frontal hemispheres; values will be assessed separately.	From baseline measurement before the nerve block until 10 minutes after return to the supine position.
Ipsilateral and Contralateral Cerebral Desaturation Burden	AUC below the desaturation threshold in the cerebral hemisphere ipsilateral and contralateral to the operated shoulder.	From baseline measurement before the nerve block until 10 minutes after return to the supine position.
Incidence of Intraoperative Hypotension and Bradycardia	Proportion of participants with hypotension, defined as a decrease in baseline systolic blood pressure of more than 20% or MAP below 65 mmHg, and bradycardia, defined as heart rate below 50 beats/min.	During the intraoperative period.
Total Intraoperative Ephedrine and Norepinephrine Dose	Total ephedrine dose in mg and total norepinephrine dose in µg administered intraoperatively.	During the intraoperative period.
Post-Anesthesia Care Unit Length of Stay	Time elapsed, in minutes, from postoperative admission to the post-anesthesia care unit to discharge to the surgical ward. Patients are discharged when the Modified Aldrete Score reaches 9 or higher.	Perioperative period (immediate postoperative recovery, from post-anesthesia care unit admission to discharge).
Modified Aldrete Score at Post-Anesthesia Care Unit Discharge	The Modified Aldrete Score is recorded at discharge from the post-anesthesia care unit to the surgical ward. The scale assesses activity, respiration, circulation, consciousness, and oxygen saturation. Each component is scored from 0 to 2, yielding a total score ranging from 0 to 10. Higher scores indicate better physiological recovery from anesthesia. Patients are discharged when the total score reaches 9 or higher.	Perioperative period (at discharge from the post-anesthesia care unit).
Assessment of cognitive functions at the 24th postoperative hour	A Mini-Mental State Examination was performed at the 24th postoperative hour to assess cognitive functions.	At the 24th postoperative hour

Collaborators and Investigators

• Sponsor: Ataturk University

Publications and helpful links

General Publications

• Murphy GS, Szokol JW, Marymont JH, Greenberg SB, Avram MJ, Vender JS, Vaughn J, Nisman M. Cerebral oxygen desaturation events assessed by near-infrared spectroscopy during shoulder arthroscopy in the beach chair and lateral decubitus positions. Anesth Analg. 2010 Aug;111(2):496-505. doi: 10.1213/ANE.0b013e3181e33bd9. Epub 2010 May 27.
• Thanaboriboon C, Vanichvithya P, Jinaworn P. What Is the Risk of Intraoperative Cerebral Oxygen Desaturation in Patients Undergoing Shoulder Surgery in the Beach Chair Position? Clin Orthop Relat Res. 2021 Dec 1;479(12):2677-2687. doi: 10.1097/CORR.0000000000001864.
• Harsanji Drenjancevic I, Drenjancevic D, Davidovic-Cvetko E, Drenjancevic I, Gulam D, Kvolik S. DOES THE ANESTHESIA TECHNIQUE AFFECT ARTERIAL PRESSURE AND REGIONAL CEREBRAL OXYGEN SATURATION DURING SHOULDER ARTHROSCOPY IN THE BEACH CHAIR POSITION? Acta Clin Croat. 2018 Sep;57(3):473-479. doi: 10.20471/acc.2018.57.03.10.

Study record dates

Study Major Dates

• Study Start (Actual): November 10, 2026
• Primary Completion (Estimated): December 29, 2026
• Study Completion (Estimated): December 29, 2026

Study Registration Dates

• First Submitted: November 3, 2026
• First Submitted That Met QC Criteria: November 10, 2026
• First Posted (Actual): November 12, 2026

Study Record Updates

• Last Update Posted (Actual): November 12, 2026
• Last Update Submitted That Met QC Criteria: November 10, 2026
• Last Verified: November 1, 2026

More Information

Terms related to this study

• Keywords: Cerebral Desaturation; Interscalene Block; Near-Infrared Spectroscopy; Shoulder Arthroscopy; Suprascapular Nerve Block; Axillary Nerve Block; Beach-Chair Position
• Other Study ID Numbers: B.30.2.ATA.0.01.00/144; 2026/5 (Other Identifier: Atatürk University Clinical Research Ethics Committee)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No