The Ultrasound-Guided Retroclavicular Block: A Prospective Feasibility Study

The aim of this feasibility study was to determine the success rate (sensory and surgical) of the novel retroclavicular block and to thoroughly describe the technique. In addition, needle tip and shaft visibility, needling time, procedural discomfort, motor block success rate, patient satisfaction at 48-hour follow-up, and complications were also recorded.

Fifty patients scheduled for distal upper limb surgery received an in-plane, single-shot, ultrasound-guided retroclavicular block with 40 mL of mepivacaine 1.5% with epinephrine 2.5 μg/mL. Block success was defined as a sensory score of 10/10 for the 5 nerves supplying the distal upper limb at 30 minutes. Surgical success, needle visibility, needling time, axillary artery depth, motor block rate, patient discomfort with technique, satisfaction at 48 hours, and complications were also recorded. All blocks were video-recorded and timed for further independent assessment. A chest x-ray was obtained before discharge.

Forty-five patients had a total sensory score of 10/10 at 30 minutes (90% success rate). Surgical success rate was 96%. Mean needling time was 3.77 minutes (25th-75th percentiles, 2.90-6.53 minutes) with a mean axillary artery depth of 3.1 ± 0.7 cm. Procedure-related discomfort (mean visual analog scale, 1.9 ± 1.2) was low. Mean 48-hour patient satisfaction rate (9.2 ± 1.1), mean needle tip (Likert scale, 3.0 ± 0.9), and shaft visibility (3.9 ± 0.9) were high. One vascular puncture and two transient paresthesias were recorded. No pneumothorax was revealed by chest x-ray.

In this study, the novel retroclavicular block offered a quick, safe, and reliable alternative for distal arm block. Further studies, comparing this approach with the classic infraclavicular block, are required to validate its efficacy, safety, and reliability.