Evaluation of pulmonary vasodilatory capacity with inhaled nitric oxide in a dog with patent ductus arteriosus.

A female Maltese dog with patent ductus arteriosus (PDA) showing left congestive heart failure and moderate pulmonary hypertension was evaluated for pulmonary vasodilatory capacity using low concentrations of inhaled nitric oxide (NO) in comparison with oxygen during preoperative cardiac catheterization. Increasing the inspired oxygen concentration (FiO2) to 1.0 without adding NO did not reduce the mean pulmonary arterial pressure (mPAP). However, inhalation of NO at FiO2 1.0 reduced mPAP rapidly without changing other hemodynamic and gas exchange parameters. From these results, inhaled NO caused selective pulmonary vasodilation without producing systemic vasodilation, which may provide a safe and effective mean of evaluating the pulmonary vasodilatory capacity of dogs with PDA.