Contralateral Horner's syndrome after ultrasound-guided right brachial plexus blockade using subscalenic approach in a dog

The objective of this case report is to describe the presentation, development and outcome of left-sided Horner's syndrome following right brachial plexus blockade using the subscalenic approach in a dog. The patient was admitted for bipedicle advancement flap of the right forelimb. An ultrasound-guided subscalenic approach for right brachial plexus nerve block was performed using 0.4 mL/kg of ropivacaine 0.375%. After extubation, the dog showed miosis, enophthalmos, palpebral ptosis and protrusion of the third eyelid of the left eye, compatible with left Horner syndrome. The dog did not seem to be uncomfortable, and about 180 minutes after extubation, when sensory function of the right forelimb was partially recovered, signs of left Horner syndrome disappeared. Six hours after extubation, the dog was discharged without any complication. To the authors' knowledge, there are no reports of contralateral Horner's syndrome after subscalenic brachial plexus blockade in dogs.