LP012 A comparative analysis of injectate spread in axillary brachial plexus block: landmark versus ultrasound-guided techniques

<h3></h3> <b>Please confirm that an ethics committee approval has been applied for or granted</b>: Yes: I’m uploading the Ethics Committee Approval as a PDF file with this abstract submission <h3>Background and Aims</h3> Ultrasound (US) guidance has modified regional anesthesia techniques. In the axillary brachial plexus block, US-guided technique targets terminal branches in the upper arm lateral to the pectoralis major, while the landmark-based technique involves perivascular needle insertion deep in the axillary fossa. Despite the differences, no study has analyzed and compared injectate spread between the two techniques. <h3>Methods</h3> Eighteen injections were performed on nine fresh human cadavers. Nine were using the landmark-based and 9 the current US-guided technique. In the landmark technique, insertion point was deep in the axillary fossa under the pectoralis major, directing the needle towards the contra-lateral shoulder. In the US-guided technique, the needle was inserted in the upper arm lateral to the pectoralis major, targeting the musculocutaneous, median, radial, and ulnar nerves. A 50 mm 22G nerve block needle was used and 20 ml of saline with 0.02% methylene blue was injected. After the injections, blunt anatomical dissection was performed to visualize spread. <h3>Results</h3> In the landmark-based technique, complete staining of the brachial plexus fascicles and axillary nerve was observed in 89% of the cases (8 out of 9). In the US-guided method, fascicle staining was considerably lower: in 11% of cases the lateral fascicle was spared; in 22% the medial fascicle; and in 56% the posterior fascicle and axillary nerve. All targeted terminal branches (100%) were stained. <h3>Conclusions</h3> Insertion point, needle direction and injectate distribution significantly differ between the two techniques. US guidance allows for selective injection of terminal branches with less proximal brachial plexus spread.