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Abstract
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Background and Aims 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.
Methods 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.
Results 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.
Conclusions 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.
Landmark-based technique
Ultrasound-guided technique