Alpha₂ agonists are commonly used in combination with other anesthetic agents to chemically immobilize wildlife and may cause potentially serious hypoxemia in wild ruminants. In some domestic ruminants, they are associated with significant changes to the pulmonary parenchyma, increased venous admixture, pulmonary edema, and hypoxemia. Effective and safe immobilization of these animals requires knowledge of the mechanisms behind these changes and the methods that offset their effects, including the use of supplemental oxygen.