Pulmonary hypertension (PH) is a consequence of an increase in pulmonary vascular resistance (PVR), pulmonary blood flow, pulmonary venous pressure, or a combination of these elements. Pulmonary arterial hypertension is a frequent complication of congenital heart disease, particularly in patients with systemic-to-pulmonary shunts. Persistent exposure o f the pulmonary vasculature to increased blood flow and pressure may result in vascular remodeling and dysfunction. This leads to increased pulmonary vascular resistance and, ultimately, to reversal of the shunt and development of Eisenmenger's syndrome. It may be more appropriate to define pulmonary hypertension according to the ratio of MPAP to mean systemic arterial pressure (MPAP/MAP) because children may have a low mean systemic blood pressure. MPAP/MAP ratio of < 0.25 is normal, a ratio of 0.33-0.5 indicates moderate pulmonary hypertension, and a ratio of > 0.5 is indicative of severe pulmonary hypertension

30 Patients were randomly allocated in two equal groups; group MS (received intravenous milrinone and oral sildenafil) and group M (received only intravenous milrinone). Demographic data, patient's clinical data and different intraoperative times were recorded. In 1st postoperative 24 hours, we recorded; hemodynamic parameters [mean pulmonary arterial pressure (MPAP), mean systemic arterial pressure (MAP), heart rate, central venous pressure]. We calculated MPAP/MAP and inotropic score. The incidence of pulmonary hypertensive crisis, side effects of studied drugs and complications related to pulmonary artery catheter were recorded.

Inclusion Criteria:

- Thirty patients in the age range 2-24 months scheduled for surgical closure of ventricular septal defect (VSD) associated with postoperative pulmonary hypertension [diagnosed in all patients by preoperative echocardiography and confirmed invasively by the pulmonary catheter before transfer to ICU by Mean Pulmonary Arterial Pressure (MPAP) > 25 mmHg or Mean Pulmonary Arterial Pressure (MPAP) /Mean Systemic Arterial Pressure (MAP) > 0.33] were enrolled in this study.

Exclusion Criteria:

• Patients with pre-existing obstructive lung disease, mitral valve disease, left ventricular dysfunction, and patients receiving preoperative pulmonary vasodilators