Dose-Finding Study: MEV90 for Local Anesthetic in Interscalene Block for Supraclavicular Nerves Block

Minimum Effective Volume (MEV90) of Local Anesthetic Required for Ultrasound-Guided Interscalene Block for Supraclavicular Nerve Block: A Dose-Finding Study

This study aims to determine the minimum effective volume (MEV90) of local anesthetic required to achieve sensory block of the supraclavicular nerves when performing a single-shot ultrasound-guided interscalene brachial plexus block (ISB). These nerves provide sensation to the skin over the clavicle and shoulder and are often involved in surgeries such as shoulder arthroscopy and clavicle repair.

Study Overview

• Status: Recruiting
• Conditions: Shoulder Surgery; Brachial Plexus Blockade; Superficial Cervical Plexus Block
• Intervention / Treatment: Drug: Ultrasound-Guided Interscalene Block with Bupivacaine

Detailed Description

This prospective dose-finding study seeks to determine the minimum effective volume (MEV90) of local anesthetic required to achieve sensory block of the supraclavicular nerves following a single-shot ultrasound-guided interscalene brachial plexus block (ISB). These nerves, branches of the superficial cervical plexus, provide cutaneous innervation over the clavicle and shoulder and may contribute to postoperative pain after shoulder and clavicular surgery. Establishing MEV90 is clinically relevant to optimize analgesia while minimizing the risk of local anesthetic systemic toxicity.

The study employs a biased coin up-and-down sequential design, commonly used in regional anesthesia dose-finding trials. The initial volume is 12 mL of bupivacaine 0.5% with epinephrine (5 µg/mL), with subsequent volumes adjusted in 2 mL increments based on the prior patient's response. The maximum permitted volume is 30 mL.

All blocks are performed under ultrasound guidance by experienced anesthesiologists (≥60 ISBs), following standard safety protocols.

This intervention does not introduce additional risk beyond routine care, as ISB is the gold standard for shoulder surgery analgesia. Results will inform whether a single interscalene injection provides adequate coverage of supraclavicular nerves or if a separate cervical plexus block is necessary for procedures involving both plexuses, such as clavicle surgery. Findings may refine volume recommendations, improve analgesic strategies, and reduce unnecessary drug exposure.

• Study Type: Interventional
• Enrollment (Estimated): 55
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Germán Aguilera, MD; Phone Number: +56985205514; Email: german.aguilera@gmail.com

Study Locations

• Chile
  • Providencia, Chile
    • Recruiting
    • Hospital del Trabajador
    • Contact: Germán Aguilera, MD; Phone Number: +56985205514

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Age ≥ 18 years
• ASA physical status I to III
• Body Mass Index (BMI) between 18 and 35 kg/m²
• Weight ≥ 50 kg
• Scheduled for shoulder arthroscopy requiring an interscalene brachial plexus block for analgesia
• Able to provide informed consent

Exclusion Criteria:

• Inability to provide informed consent
• Coagulopathy (platelet count ≤100,000; INR ≥1.4)
• Significant pulmonary disease (restrictive or obstructive)
• Renal insufficiency (creatinine ≥1.2 mg/dL)
• Hepatic insufficiency (transaminases ≥100 U/L)
• Allergy to local anesthetics
• Pregnancy
• Pre-existing neuropathy
• Previous surgery in ipsilateral cervical or supraclavicular region
• Contralateral hemidiaphragmatic paralysis or vocal cord paralysis

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Supportive Care
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Minimum Effective Volume 90 (MEV90); Participants in this arm will receive a single-shot ultrasound-guided interscalene brachial plexus block as part of standard perioperative analgesia for shoulder arthroscopy. The intervention consists of injecting bupivacaine 0.5% with epinephrine (5 µg/mL) between the anterior and middle scalene muscles at the level of the C5-C6 nerve roots, using an in-plane technique under real-time ultrasound guidance.

Drug: Ultrasound-Guided Interscalene Block with Bupivacaine; Participants will receive a single-shot interscalene brachial plexus block performed under real-time ultrasound guidance. The block targets the C5-C6 nerve roots between the anterior and middle scalene muscles using an in-plane technique. The local anesthetic is bupivacaine 0.5% with epinephrine (5 µg/mL). The injected volume ranges from 12 mL to 30 mL, determined by a dose-finding algorithm (biased coin up-and-down sequential design) to calculate the minimum effective volume (MEV90) for supraclavicular nerve block. All procedures are performed by experienced anesthesiologists following standard safety protocols, including incremental injection with aspiration and continuous monitoring (ECG, SpO₂, non-invasive blood pressure).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Minimum Effective Volume (MEV90) for Supraclavicular Nerve Block via Interscalene Approach	The primary outcome is the calculation of the minimum effective volume of local anesthetic (MEV90) required to achieve complete sensory block of the supraclavicular nerves following a single-shot ultrasound-guided interscalene brachial plexus block. Success is defined as absence of cold and touch sensation at the midpoint of the clavicle, assessed using an ice test.	30 minutes after completion of the block

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Sensorimotor Block Score for Interscalene Block	Composite score (0-8 points) assessing sensory and motor block in C5-C6 dermatomes using ice test and motor function (shoulder abduction and external rotation). Success defined as ≥6 points.	Every 5 minutes up to 30 minutes after block completion.
Onset Time of Sensorimotor Block	Interval (minutes) between completion of local anesthetic injection and achievement of ≥6 points on the sensorimotor scale.	Up to 30 minutes after block completion.
Sensory Block at Shoulder Arthroscopy Portals	Presence or absence of cold and touch sensation at anterior, lateral, and posterior portal sites using ice test.	30 minutes after block completion.
Sensory Block of Auricular, Occipital, and Transverse Cervical Nerves	Assessment of sensory block in territories of auricular major, occipital minor, and transverse cervical nerves using ice test.	30 minutes after block completion.
Pain Score During Block Procedure	Patient-reported pain during needle insertion and injection, measured using Visual Analog Scale (VAS, 0-10).	Immediately after block completion.
Block Performance Times	Time intervals for image acquisition, needle placement, and total block execution (minutes).	During block procedure.
Incidence of Block-Related Adverse Events	Occurrence of complications including Horner's syndrome, hoarseness, dyspnea, vascular puncture, hematoma, paresthesia, and symptoms of local anesthetic systemic toxicity (LAST).	From block completion until end of surgery.

Collaborators and Investigators

• Sponsor: Hospital del Trabajador de Santiago

Study record dates

Study Major Dates

• Study Start (Estimated): April 1, 2026
• Primary Completion (Estimated): November 1, 2026
• Study Completion (Estimated): December 1, 2026

Study Registration Dates

• First Submitted: January 4, 2026
• First Submitted That Met QC Criteria: January 4, 2026
• First Posted (Actual): January 14, 2026

Study Record Updates

• Last Update Posted (Actual): April 8, 2026
• Last Update Submitted That Met QC Criteria: April 6, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Shoulder Surgery; Interscalene Block; Brachial Plexus Blockade; Supraclavicular nerves block; Miminum Effective Volume 90; MEV90
• Additional Relevant MeSH Terms: Organic Chemicals; Anilides; Amides; Aniline Compounds; Amines; Bupivacaine
• Other Study ID Numbers: Project Nº34, 2025; 251213001 (Other Identifier: Comité Ético Científico de Ciencias de la Salud - Universidad Católica)

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