A novel approach to ear pain in the horse: A case report

Abstract

Background: During electrochemotherapy (ECT), a chemotherapeutic drug is injected into the tumor and then an electroporation is provided. In horses, ear manipulation may be very painful, and combining a loco-regional technique with sedation might be a good option to avoid anesthesia-related risks. A two-injection-point block of the internal and external pinna and acoustic meatus was described in horse cadavers, and it permitted complete stain of all three branches of the great auricular nerve (GAN), internal auricular nerve branch (IAB), lateral auricular branch (LAB), and caudal auricular nerve (CAN), suggesting a lower risk of intra-parotid injection during the IAB and LAB block.

Case description: An 8-year-old Italian jumping gelding presented for ECT to treat a fibroblastic sarcoid in the left medial pinna. After intravenous sedation with acepromazine, romifidine, and butorphanol, a two-injection-point block was provided as previously described. The block of the GAN was blind, whereas an electrical nerve locator was used for the IAB, LAB, and CAN. A total of 12 ml of 0.5% ropivacaine was injected. The ECT was safely performed without any difficulties. The horse well tolerated the procedure and completely recovered 75 minutes after sedation. No complications were detected.

Conclusion: The described approach seems feasible and suitable for the blockade of the sensory innervation of the equine ear in the case of ECT.

Keywords: Auricular blocks; Ear; Electrochemotherapy; Horse; Ropivacaine.

Fig. 1.. After palpating the cranial aspect of the atlas wing, the GAN and its branches were localized, and the first injection of 0.5% ropivacaine (6 ml) was performed. A second injection at the caudal base of the ear was performed to block the IAB, LAB, and CAN. The needle was inserted through the skin once the parotid gland was palpated, then it was advanced in a sagittal direction, parallelly to the ear canal until its tip was just above the parotid gland (about 2 cm deep). When medio-lateral twitch of the pinna was well elicited at a current of 0.4 mA, 6 ml of 0.5% ropivacaine was slowly administered.