PURPOSE:Persistent pulmonary hypertension of the newborn (PPHN) is life threatening neonatal disease. Nitric oxide (NO) has been proven to improve oxygenation, however its usage is limited and 30% of patients with PPHN are NO nonresponders. Milrinone decreases right ventricular afterload and has selective pulmonary vasodilator effect. We studied the effects of milrinone on neonates with respiratory failure originated in PPHN. METHODS:Six neonates, who had oxygen index above 20 and responded poorly to other management, were treated with intravenous milrinone after confirming pulmonary hypertension with echocardiography. We reviewed their medical records retrospectively. Intravenous milrinone was started at a dose of 0.375 microgram/kg/min. Respiratory indices (Oxygenation index [OI], ventilation settings, and arterial blood gas) and cardiovascular stability (mean arterial pressure and heart rate) were documented just before; and at 6, 12, 24, 36, 48, and 72 hours after commencement of milrinone therapy. The primary outcome was the effect of milrinone on oxygenation, which was 40% reduction in OI. RESULTS:Primary cause of PPHN was meconium aspiration syndrome in three infants, respiratory distress syndrome (RDS) in the other three. Milrinone was commenced at a median age of 22.3+/-6.1 hours with a dose of 0.375 microgram/kg/min except one infant (0.5 microgram/kg/min) and infants were treated for median 58.3+/-16.7 hours. OI of all infants showed 40% reduction within 24 hours. There were no mortality, and no infants with hypotension, and intraventricular hemorrhage. CONCLUSION:Milrinone proved to be effective for PPHN by improving oxygenation. It did not cause any complications in clinical trials for newborns. It is suggested that Milrinone can replace NO or can be used as adjunct to NO in the treatment of PPHN.