Mast cell tumors are one of the most common skin malignancies diagnosed in dogs, and surgical excision is commonly performed in the veterinary practice setting. Surgical manipulation of the tumor can cause mast cell degranulation and release of various bioactive substances including histamine. It is common practice for many to administer an antihistamine preoperatively to prevent the cardiovascular effects of histamine including vasodilation and hypotension. In this Specialty Update veterinary anesthesiology expert Dr. Alexander Valverde discusses his approach in managing patients undergoing anesthesia for mast cell tumor excision. In addition to suggested anesthetic drug protocols, he reveals the findings of a clinical study that examined the effects of diphenhydramine in dogs undergoing cutaneous mast cell tumor excision and shares his recommendations based on these findings. Running time: 27 mins Member Fee: $14.95; Free registration for Premium VetVine Membership subscribers http://vetvine.com/article/181/evidence-based-update-subscriptions