Ultrasonographic study of a modified axillary approach to block the major branches of the brachial plexus in dogs.

Objective: To provide ultrasonographic mapping of the axillary region of dogs to facilitate identification of the major branches of the brachial plexus in relation to the axillary artery.

Study Design: Prospective study.

Animals: A total of two dog cadavers and 50 client-owned, healthy dogs weighing >15 kg.

Methods: In Phase 1, anatomical dissections were performed to identify the relation of the major brachial plexus nerves to the axillary artery. In Phase 2, with the dogs in dorsal recumbency with thoracic limbs flexed naturally, the axillary space was scanned using a linear array probe oriented on the parasagittal plane until the axis transverse to nerves was found. Then, the transducer was rotated to a slight lateral angle approximately 30° to midline. The examination aimed to identify the axillary artery and the musculocutaneous, radial, median and ulnar nerves in addition to determining their position and distribution in four predefined sectors.

Results: The musculocutaneous nerve was observed in all animals cranial to the axillary artery. The radial, ulnar and median nerves were distributed around the axillary artery, with >90% on the caudal aspect of the axillary artery (sectors 1 and 2).

Conclusions And Clinical Relevance: Ultrasonography identified the location of the brachial plexus nerves near the studied sectors, providing useful guidance for performing a brachial plexus nerve block.