• Susanne Retter, Jennifer Szerb, Kwesi Kwofie, Patricia Colp, Robert Sandeski, and Vishal Uppal.
• Department of Anaesthesia, Pain Management and Perioperative Medicine, Halifax, NS, Canada.
• Br J Anaesth. 2019 Jun 1; 122 (6): 776-781.

BackgroundMulti-injection targeted intracluster injection ultrasound-guided supraclavicular brachial plexus block has been advocated to provide a faster onset of anaesthesia compared with a double injection technique. By placing the needle within clusters of hypoechoic structures, corresponding to neural tissue, this technique may increase needle trauma and the incidence of nerve injury. This study assessed the rate of sub-perineural needle placement with a single intracluster brachial plexus injection in the supraclavicular fossa of human cadavers.MethodsA single ultrasound-guided intracluster brachial plexus injection was performed bilaterally at the supraclavicular fossa on 21 lightly embalmed clinical grade cadavers. Using an in-plane technique, an echogenic needle was positioned to target the middle or lower trunk 'cluster', where 0.2 ml black India ink was injected. An effort was taken to avoid the hypoechoic structures with the needle tip. Tissue samples were assessed histologically by two experienced reviewers.ResultsAll 42 injections were sonographically assessed to be within the 'main cluster'. Ink was extra-epineural in 13/41 (32%), sub-epineural but outside perineurium in 18/41 (44%), and sub-perineural in 10/41 sections (24%; 95% confidence interval, 13-41%). The histology from one injection was uninterpretable. Of the 10 sub-perineural deposits, the ink was intrafascicular in nine sections.ConclusionsWe observed a high rate of sub-perineural injection with a single intracluster injection. Thus the targeted intracluster injection supraclavicular block cannot be recommended until further evidence is available regarding the safety of this technique.Copyright © 2019 British Journal of Anaesthesia. Published by Elsevier Ltd. All rights reserved.

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