Effects of Imagent® on pulmonary hemodynamics and gas exchange in dogs

Imagent® is an IV injected contrast echocardiography agent designed to image the left ventricle after traversing the pulmonary circulation. We examined the effect of Imagent® on pulmonary function by injecting either Imagent® (n = 8) or equivalent volume of saline (n = 7) IV in randomly ordered 1, 8 and 16 mg/kg doses in dogs with preexisting pulmonary hypertension. We found that Imagent® had no effects on cardiac output, pulmonary gas exchange, lung wet:dry ratio or static compliance. However, the 16 mg/kg dose of Imagent® increased both pulmonary artery pressure (PAP) transiently by an average of 5.7 mmHg (p < 0.05) 2 to 3 min after injection and pulmonary vascular resistance (PVR) by 5.9 mmHg per l/min (p < 0.05) 4 min after injection before returning to preinjection levels. The lower doses of Imagent® did not affect PAP or PVR. These results imply that the approved clinical dose of Imagent® (0.125 mg/kg) will not affect pulmonary hemodynamics, gas exchange or mechanical properties in dogs with preexisting pulmonary hypertension. (E-mail: pdwagner@ucsd.edu)