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.

The use of ultrasound to assist epidural injection in obese dogs.

OBJECTIVE: To evaluate the use of ultrasound for identifying the site for needle puncture and to determine the depth to the epidural space in obese dogs. STUDY DESIGN: Prospective study in dogs undergoing elective orthopedic surgery. ANIMALS: A group of seven obese Labrador male dogs aged 6.93 ± 2.56 years and weighing 46.5 ± 4.1 kg (mean ± standard deviation). METHODS: The anesthetic protocol for these dogs included epidural anesthesia. With the dogs anesthetized and positioned in sternal recumbency with the pelvic limbs flexed forward, ultrasound imaging was used to locate the lumbosacral intervertebral space. Intersection of dorsal and transverse lines about the probe identified the point of needle insertion. A 17 gauge, 8.9 cm Tuohy needle was inserted perpendicularly through the skin and advanced to the lumbosacral intervertebral space. The number of puncture attempts was recorded and needle depth was compared with skin to ligamentum flavum distance. RESULTS: Epidural injection was performed in all dogs at the first attempt of needle insertion. The distance from skin to epidural space was 5.95 ± 0.62 cm measured by ultrasound and 5.89 ± 0.64 cm measured with the Tuohy needle. These measurements were not different (p = 0.26). A highly significant correlation coefficient of 0.966 between measurement techniques was obtained (p < 0.001). CONCLUSIONS AND CLINICAL RELEVANCE: Ultrasound imaging identified the point of needle insertion for lumbosacral epidural injection in seven obese dogs. The results indicate that ultrasound can be used to locate the lumbosacral intervertebral space and identify an appropriate point for needle insertion to perform epidural injection.