<qa>  What is the first RCT of iloprost for inhalation after surgery ofPulmonary hypertension is a serious postoperative complication in children with congenital heart defects, which has a high incidence and mortality. Iloprost is a prostacyclin analogue. When applied by inhalation, it selectively dilates pulmonary vessels, without side affecting the systemic circulation. No randomized controlled trials RCT of iloprost have previously been performed in this indication. The investigators study is the first RCT of iloprost for inhalation after surgery of childrens congenital heart diseases to be performed in this field. 