Effects of ouabain on pulmonary haemodynamics in patients with hypoxic pulmonary hypertension

Differing opinions about the use of digitalis in patients with cor pulmonale have led the authors to study haemodynamic effect of strophantin, a cardiotonic glycoside used as therapy of choice of decompensated cor pulmonale. Five patients with severe airways obstruction recovering from heart failure were studied. Ouabain at a dose of 0.01 mg/kg was infused into the pulmonary artery. Pulmonary artery pressure and flow were measured before, at the end of the infusion, 15 and 30 min after it. There was no change in the heart rate or mean pulmonary artery pressure and a slight increase in the pulmonary wedge pressure was observed after ouabain. The most important change concerned the pulmonary blood flow. The cardiac index rose from the initial 2.48 +/- 0.44 l/min/m2 to 3.67 +/- 1.3 l/min/m2 15 min after ouabain. The increase in cardiac output was entirely due to the increase in the stroke volume. Pulmonary vascular resistance fell from 502 +/- 208 dyn. s. cm-5 to 315 +/- 216 dyn. s. cm-5 15 min after ouabain. The findings support clinical preference for strophantin in patients with decompensated cor pulmonale.