Description of an ultrasound-guided maxillary nerve block in dogs: a cadaveric study and case series

To describe an ultrasound-guided in-plane technique for maxillary nerve block in dogs and its clinical analgesic application.

Descriptive anatomical study and retrospective case series.

A group of 12 canine cadavers and six client-owned dogs.

Cadavers were placed in lateral recumbency, and the ultrasound transducer was positioned transversely across the head, ventral to the zygomatic arch and cranial to the mandible to visualize the pterygopalatine fossa. The fascial plane between the zygomatic gland and medial pterygoid muscle was identified, and a 22 gauge, 50 mm insulated needle was advanced in-plane to inject 0.1 mL of a 1:1 dye-saline per hemimaxilla. Injection success was assessed by staining of the maxillary nerve or its perineural fascia during dissection. Clinical anaesthesia records from six dogs undergoing maxillofacial procedures were reviewed retrospectively. Blocks were performed using the pulsation of the maxillary artery as a sonographic landmark. Block success was defined as absence of nociceptive response to upper lip pinching postoperatively. Staining success is presented as numbers and percentages (n/n, %).

In the cadavers, 14/24 injections (58.3%) resulted in maxillary nerve or perineural fascia staining. In the clinical series, median body mass was 26.6 (range: 4.4-34.8 kg). A total of nine blocks were performed in six dogs using 0.5% bupivacaine (0.06-0.2 mL kg^-1): bilateral blocks in three dogs and unilateral blocks in three dogs. All dogs (9/9, 100%) demonstrated postoperative sensory blockade; however, two dogs required intraoperative fentanyl.

This ultrasound-guided in-plane approach achieved a moderate success rate in cadavers. In vivo, the pulsatile maxillary artery served as a reliable landmark for injection with consistent postoperative sensory blockade. The technique appears feasible and may represent a clinically effective alternative to traditional blind approaches.