Ultrasound-guided cervical plexus associated block in dogs: A preliminary cadaveric study.

Objectives: To describe the ultrasonographic anatomy of the neck region in dogs and to determine the feasibility of an injection targeted to the cervical plexus.

Study design: Prospective cadaveric study.

Animals: A group of six mixed-breed mesocephalic dog cadavers.

Methods: Cadavers were assigned to a size category according to body weight (small, ≤10 kg; medium, 10.1-24 kg; large, > 24.1 kg) and placed in lateral recumbency. A linear probe was placed over the wing of the atlas perpendicular to the spine and slid caudally to identify the transverse process of the fourth cervical vertebra. A 22 gauge, 70 mm spinal needle was introduced in-plane and advanced in a dorso-ventral direction, reaching the cervical fascia (CF). According to the size category, 2.5 mL, 5 mL or 10 mL of 0.15% methylene blue was injected within the CF and between the intertransversarius ventralis and longus colli muscles. Each cadaver was injected bilaterally. Staining of the second (C2), third (C3) and fourth (C4) cervical ventral branches was assessed by anatomical dissection.

Results: Each size category included two cadavers: 8 kg and 10 kg in the small category; 15 kg and 19 kg in the medium category; and 26 kg and 37 kg in the large category. Nerve staining resulted only from injection within the CF. In all cadavers, 100% of the ventral rami of the second (12/12), third (12/12) and fourth (12/12) cervical nerves were stained circumferentially for > 2 cm. In the smallest cadaver, the dye reached the atlas cranially.

Conclusions and clinical relevance: The described injection within the CF stained the cervical plexus and appears a feasible locoregional technique in dogs.