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

Hospital del Trabajador de Santiago

Status: Not yet enrolling

Conditions: Superficial Cervical Plexus Block; Shoulder Surgery; Brachial Plexus Blockade

Treatments: Drug: Ultrasound-Guided Interscalene Block with Bupivacaine

Study type: Interventional

Funder types: Other

Identifiers

NCT07338916

251213001 (Other Identifier)

Project Nº34, 2025

Details and patient eligibility

About

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.

Full 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.

Enrollment: 55 estimated patients

Sex: All

Ages: 18+ years old

Volunteers: No Healthy Volunteers

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

Trial design

Primary purpose: Supportive Care

Allocation: N/A

Interventional model: Single Group Assignment

Masking: None (Open label)

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55 participants in 1 patient group

Minimum Effective Volume 90 (MEV90)

Experimental group

Description:

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.

Treatment:

Drug: Ultrasound-Guided Interscalene Block with Bupivacaine