Bronchopulmonary Effects of Digitalis in the Anesthetized Dog

¹ Department of Pharmacology, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania

Digoxin and acetyl strophanthidin were tested on the canine lung because of the possibility of cardiac glycosides having some undesired action in patients with cor pulmonale. Both glycosides cause an increase in pulmonary resistance in the dog with intact or cut vagus. Atropine and sotalol did not interfere with the response. The increase in pulmonary resistance is explained by a direct effect of digitalis on the bronchial smooth muscle. The accompanying decrease in pulmonary compliance is independent of any change in pulmonary blood flow because the response could still be elicited in the dog with right heart bypass. In such a preparation, acetyl strophanthidin caused a variable effect on pulmonary vascular resistance possibly because the extracorporeal circulation may have altered the ability to maintain an adequate dose in the pulmonary blood vessels.