Brachial Plexus Blockade, Shoulder Surgery, Superficial Cervical Plexus Block
Conditions
Keywords
Interscalene Block, Brachial Plexus Blockade, Supraclavicular nerves block, Shoulder Surgery, Miminum Effective Volume 90, MEV90
Brief summary
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.
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.
Interventions
DRUGUltrasound-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).
Sponsors
Hospital del Trabajador de Santiago
Study design
Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
SUPPORTIVE_CARE
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Minimum Effective Volume (MEV90) for Supraclavicular Nerve Block via Interscalene Approach | 30 minutes after completion of the block | 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. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Sensorimotor Block Score for Interscalene Block | Every 5 minutes up to 30 minutes after block completion. | 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. |
| Onset Time of Sensorimotor Block | Up to 30 minutes after block completion. | Interval (minutes) between completion of local anesthetic injection and achievement of ≥6 points on the sensorimotor scale. |
| Sensory Block at Shoulder Arthroscopy Portals | 30 minutes after block completion. | Presence or absence of cold and touch sensation at anterior, lateral, and posterior portal sites using ice test. |
| Sensory Block of Auricular, Occipital, and Transverse Cervical Nerves | 30 minutes after block completion. | Assessment of sensory block in territories of auricular major, occipital minor, and transverse cervical nerves using ice test. |
| Pain Score During Block Procedure | Immediately after block completion. | Patient-reported pain during needle insertion and injection, measured using Visual Analog Scale (VAS, 0-10). |
| Block Performance Times | During block procedure. | Time intervals for image acquisition, needle placement, and total block execution (minutes). |
| Incidence of Block-Related Adverse Events | From block completion until end of surgery. | Occurrence of complications including Horner's syndrome, hoarseness, dyspnea, vascular puncture, hematoma, paresthesia, and symptoms of local anesthetic systemic toxicity (LAST). |
Countries
Chile
Contacts
CONTACTGermán Aguilera, MD
Outcome results
None listed