Background and Objectives This prospective, randomized trial compared ultrasound-guided targeted intracluster injection (TII) supraclavicular brachial plexus block (SCB) and infraclavicular brachial plexus block (ICB).

Methods Sixty-four patients were randomly allocated to receive an ultrasound-guided TII SCB (n = 32) or ICB (n = 32). The local anesthetic agent (lidocaine 1.5% with epinephrine 5 μg/mL) was identical in all subjects. In the TII SCB group, half the volume (16 mL) was injected inside the largest neural cluster (confluence of trunks and divisions of the brachial plexus). Subsequently, the remaining half (16 mL) was divided into equal aliquots and injected inside every single satellite cluster. In the ICB group, the entire volume (35 mL) was injected dorsal to the axillary artery. During the performance of the block, the performance time, number of needle passes, procedural pain, and complications (vascular puncture, paresthesia) were recorded. Subsequently, a blinded observer assessed the onset time, incidence of Horner syndrome, and success rate (surgical anesthesia). The main outcome variable was the total anesthesia-related time (sum of performance and onset times).

Results Due to a quicker onset [8.9 (5.6) vs 17.6 (5.3) minutes; P < 0.001], the total anesthesia-related time was shorter with TII SCB [18.2 (6.1) vs 22.8 (5.3) minutes; P < 0.001]. However no differences were observed between the 2 groups in terms of success rate (93.7%–96.9%), block-related pain scores, and adverse events such as vascular puncture and paresthesia. Expectedly, the ICB group required fewer needle passes (2 vs 6; P < 0.001) as well as shorter needling [4.8 (2.3) vs 9.0 (2.9) minutes; P < 0.001] and performance [5.6 (2.3) vs 9.5 (2.9) minutes; P < 0.001] times. Moreover, the ICB approach was associated with a decreased incidence of Horner syndrome (3.1% vs 53.1%; P < 0.001).

Conclusions Ultrasound-guided TII SCB and ICB provide comparable success rates. Due to its quick onset, TII SCB results in a shorter total anesthesia-related time.