Dyspnea Induced by Alpha 2-Adrenergic Agonists and Dissociative Anesthetics Combination in Dogs and Cats

This case report describes the potential adverse effects of the combination of alpha 2-adrenergic agonists and dissociative anesthetics and discusses its prevention. The cases of 2 dogs and 3 cats, including 4 juvenile (<7 months old) animals and 1 adult cat (2 years old), that presented with dyspnea immediately after induction at local veterinary clinics and were referred to the Seoul National University Veterinary Medicine Teaching Hospital are described. Four animals were premedicated with atropine, and all were anesthetized intravenously using a combination of an alpha 2-adrenergic agonist (medetomidine or xylazine) and a dissociative anesthetic (ketamine or Zoletil^®). Both dogs developed immediate epistaxis, dyspnea, and radiographic evidence of diffuse alveolar infiltration. One dog was euthanized after experiencing seizures. All 3 cats developed anorexia followed by dyspnea within 24 to 48 h post-anesthesia, resulting in death in 2 cats, while 1 cat recovered with symptomatic treatment. The sympathomimetic effects of dissociative anesthetics and vasoconstrictive alpha 2-adrenergic agonists can cause transient hypertension, which can precipitate pulmonary edema and hemorrhage, leading to dyspnea. Either juvenile or atropine-premedicated patients may be at an increased risk, warranting dose adjustment, route selection, and careful monitoring during anesthesia.