Objective To study the therapeutic effects of inhaled iloprost on pediatric pulmonary hypertension after congenital heart disease operation and to investigate the mechanisms of iloprost.Methods Thirteen 10 min every time,every 4 hours for 48 h after the surgery.We used the 24 h cardiac monitoring and ultrasonic cardiography for hemodynamical monitoring.We examined the blood cAMP and cGMP by ELISA assay.Results The patients were(17.88±12.56) months old with average weight of(9.29±3.59) kg.The right atrial pressure,systolic pulmonary arterial pressure,systolic pulmonary arterial pressure/systolic blood pressure were(11.5±1.41)mm Hg,(61.64±13.6) mm Hg and 0.66±0.16 before the treatment and they were(9.88±1.88) mm Hg,(47.67±12.18) mm Hg and 0.52±0.15 at the time point of 20 min after the treatment.For all the three parameters,there were significant differences before and after treatment.The effect of iloprost continues to 120 min later.The cAMP level was(335.75±127.31) μg/L before iloprost inhalation and increased to(519.68±148.54)μg/L at the time point of 20 min after inhaling iloprost,showing a significant difference(P＜0.01).Blood pressure,cGMP level and ventilator parameters showed no notable difference before and after the treatment.Conclusion Inhaled iloprost significantly improves pulmonary hemodynamics in children with pulmonary hypertension after congenital heart disease operation,which might be achieved by increasing the blood cAMP.However,systemic blood pressure and respiratory function keep unaffected after iloprost inhalation.