Ultrasound guided posterior approach to the infraclavicular brachial plexus

During conventional ultrasound guided approaches to the infraclavicular brachial plexus the needle is acutely angled to the ultrasound beam, making needle tip visualisation difficult. This limitation can be overcome by changing the insertion point so that the needle passes perpendicular to the ultrasound beam. The ultrasound probe is placed on the anterior shoulder inferior to the clavicle and medial to the coracoid process (Fig. 1). The axillary vessels are identified in cross-section in the parasagittal plane. The ultrasound probe may be scanned medially at this point to confirm adequate separation from the pleural cavity and ribs. Position of the patient, probe, and ultrasound machine prior to performing the block. The needle insertion point is over the trapezius muscle sufficiently posterior to allow the needle to pass between the clavicle and the scapula in the direction of the axillary artery (Fig. 2). The insertion point is strictly aligned with the long axis of the ultrasound beam. The approximate insertion length to pass into the ultrasound beam is noted, about 30–40 mm. With the probe in one hand and needle in the other, a 100-mm needle is inserted in the inferior direction to the predetermined depth for initial visualisation and the probe alignment is manipulated until the needle is seen prominently in long axis in the ultrasound image. The needle is then manipulated to approach the brachial plexus (Fig. 3). If the scapula obstructs the needle, a sandbag placed to elevate the shoulder increases the gap between the scapula and clavicle, or a more medial approach may be used. Parasagittal section through the shoulder medial to the coracoid process showing block needle and ultrasound probe. Ultrasound image of block needle approaching the neurovascular bundle. The block is completed using visual perineural targeting of the nerve cords, a nerve stimulator or by perivascular infiltration. The local anaesthetic solution is seen as a black space surrounding the nerves (Fig. 4). Although the block needle passes through a longer course to reach the target, the superior visualisation of the entire tip section of the needle allows more confident alignment relative to neurovascular structures. The block needle is also more easily directed posterior to the artery than when using the conventional approach. Ultrasound image of local anaesthetic injected around the brachial plexus. Further information on this and other new ultrasound guided approaches may be found at http://www.heartweb.com.au