A Technique for Ultrasound-guided Paravertebral Brachial Plexus Injections in Dogs

Using cadaveric dogs, we established the ultrasonographic landmarks for performing paravertebral injections around the brachial plexus nerve roots in the dog, and assessed the accuracy and regional spread of the aliquots. A mixture of methylene blue dye and an iodinated contrast medium was used as the injectate. A 0.3 ml volume was used to assess accuracy and a 3.0 ml volume was used to assess regional spread. Accuracy and regional spread were assessed from computed tomography (CT) images acquired after injection by measuring the distance from each foramen to the nearest edge of contrast medium, and the dimensions of spread of contrast medium in each anatomic plane, respectively. The mean distance of small volume injections from each foramen was 0.9 cm (standard deviation [SD] 0.56 cm). The mean spread of contrast medium for the small volume injections measured 1.7 cm (SD 0.6 cm) cranial-to-caudal, 1.2 cm (SD 0.4 cm) dorsal-to-ventral and 7.4 cm (SD 0.4 cm) medial-to-lateral. The mean spread of contrast medium for the combined three large volume injections measured 7.4 cm (SD 1.7 cm) cranial-to-caudal, 3.1 cm (SD 0.8 cm) medial-to-lateral, and 2.8 cm (SD 0.5 cm) dorsal-to-ventral. After the CT studies, staining of each nerve root and any other regional structure was assessed grossly. Based on our results, ultrasound can be used to guide injections around the nerve roots of the brachial plexus in dogs.