Modified technique for proximal subclavicular brachial plexus block: study on unfixed cadavers

BACKGROUND: The proximal subclavian brachial plexus block is performed deep and posterior to the midpoint of the clavicle. Only a few studies evaluated the spread of local anesthetic when using a proximal subclavian approach to the brachial plexus. We performed a cadaveric study to evaluate the spread of the injection after performing proximal subclavian brachial plexus block using ultrasound navigation.

AIM: To examine the spread of the stained solution in unfixed corpses, when it is administered using a modified technique of proximal subclavian access to the brachial plexus using ultrasound navigation.

MATERIALS AND METHODS: Six ultrasound-guided injections were performed on three unfixed cadavers using 20 ml of a colored solution. The brachial plexus and its branches were distinguished from the level of the midpoint of the clavicle to the upper third of the shoulder. The boundaries of ink distribution in relation to the bundles and terminal branches of the brachial plexus from the intersection of the upper edge of the clavicle to the upper parts of the axillary region were assessed.

RESULTS: In all cases of dye spread, the lateral, posterior, and medial bundles of the brachial plexus were stained. Terminal branch staining varied and was limited to the proximal portions of these nerves. The dye spread to the interstellar space in 2 (33%) out of 6 (100%) injections and to the level of the upper edge of the clavicle in 4 (67%) injections. The axillary and radial nerves were stained in all injections, and the ulnar nerve was stained in 4 (67%) of 6 (100%) injections. The musculocutaneous and median nerves were stained in only 2 (33%) of 6 (100%) injections. No phrenic nerve staining was observed in any case.

CONCLUSIONS: On the basis of experiment results on unfixed cadavers, injection using a modified ultrasound-guided proximal subclavian approach can fill the fascial sheath surrounding the brachial plexus with the injection material, thus causing the dye to spread around all bundles of the brachial plexus to supraclavicular space. Additional research is needed to assess whether high injection volumes or multiple injection sites can affect distribution.