Indirect versus direct measurement of brachial plexus depth

Supraclavicular nerve blocks are effective but may be complicated by pneumo thorax. We hypothesized that, to avoid this complication, the depths of the brachial plexus and the lung could be estimated to guide needle placement. In 17 patients undergoing surgical relief of thoracic outlet syndrome, we designated a point on the skin midway between the clavicle and the trapeziu s muscle, in line with the most lateral point of the arterial pulsation in the supraclavicular fossa, to make preoperative height measurements relativ e to the clavicle and then intraoperative depth measurements of the plexus, artery, and pleura. The height of the reference point above the top of cla vicle did not differ significantly from the depth of the plexus. The height of the reference point above the top, middle, and bottom of the clavicle d iffered significantly from the pleural depth (P = 0.0001, P = 0.0001, P = 0 .0005, respectively). Patient weight correlated significantly with the dept h of the plexus (P = 0.004, r(2) = 0.45), artery (P = 0.0003, r(2) = 0.42), and pleura (P = 0.0003, r(2) = 0.58). We conclude that it is possible to a ccurately estimate the depth of the brachial plexus in the supraclavicular fossa. Implications: In this study, we sought to minimize the risk of pneum othorax when approaching the brachial plexus through the supraclavicular fo ssa by developing a technique that could accurately estimate the depth of t he nerves, within a range that is well clear of the lung.