The Efficacy of Personalized Local Anesthetic Dosing Based on Ultrasound-Measured Nerve Cross-Sectional Area in Brachial Plexus Block: a Non-Inferiority Randomized Controlled Trial.

Condition(s) studied

Investigational drug(s) / intervention(s)

CSA-based dosing of Ropivacaine: Participants assigned to this group will receive an ultrasound-guided interscalene brachial plexus block. First, the cross-sectional area (CSA) of the brachial plexus nerves at the interscalene groove will be measured in the short-axis view using ultrasound. The dose of 0.5% ropivacaine will then be calculated individually using the formula: Volume (mL) = CSA (mm²) × K, where K is a conversion coefficient (in mL/mm²) determined from a prior pilot dose-finding study. The total administered dose will not exceed the maximum recommended safe dose of ropivacaine (225 mg). The block will be performed by an experienced anesthesiologist under real-time ultrasound guidance.

Experience-based dosing of Ropivacaine: Participants assigned to this group will receive an ultrasound-guided interscalene brachial plexus block. The volume of 0.5% ropivacaine to be injected will be determined solely by the clinical judgment and experience of the attending anesthesiologist, reflecting standard real-world practice. The total administered dose will not exceed the maximum recommended safe dose of ropivacaine (225 mg). The block will be performed by an experienced anesthesiologist under real-time ultrasound guidance.

Weight-based dosing of Ropivacaine: Participants assigned to this group will receive an ultrasound-guided interscalene brachial plexus block. The dose of 0.5% ropivacaine will be calculated based on the participant's body weight using the standard formula: Dose (mg) = 2.5 mg/kg. The corresponding volume will then be administered. The total administered dose will not exceed the maximum recommended safe dose of ropivacaine (225 mg). The block will be performed by an experienced anesthesiologist under real-time ultrasound guidance.

Study summary

This is a prospective, randomized, assessor-blinded, three-arm, non-inferiority clinical trial. The study aims to compare the effectiveness and safety of an individualized dosing strategy for local anesthetic in brachial plexus blocks against two standard methods. The experimental intervention uses ultrasound to measure the cross-sectional area (CSA) of the brachial plexus nerves to calculate a patient-specific dose of 0.5% ropivacaine. This is compared to a standard weight-based dosing regimen (2.5 mg/kg) and dosing based on the anesthesiologist's clinical experience. A total of 350 adult patients scheduled for elective unilateral upper limb surgery will be randomly assigned to one of the three groups. The primary outcome is the success rate of the nerve block 30 minutes after administration. Secondary outcomes include assessments of diaphragmatic function, postoperative pain scores, the incidence of complications (such as nerve involvement or systemic toxicity), and patient satisfaction. The hypothesis is that the CSA-based dosing method will be non-inferior to the conventional methods in achieving successful anesthesia while potentially optimizing drug dosage.

Eligibility

Primary outcome measure(s)

• Block Success Rate — At 30 minutes after block completion

Trial sites (1)

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