Circulatory effects of inhaled iloprost in the newborn preterm lamb

Inhaled NO (iNO) has an established role in the treatment of pulmonary hypertension (PH) in the newborn. However, costs and potential toxicity associated with iNO have generated interest in alternative inhaled selective pulmonary vasodilators such as iloprost. In a preterm lamb model of respiratory distress syndrome, we studied effects of increasing doses of iloprost followed by iNO on right ventricular pressure (RVP) and circulation including cerebral oxygenation. Fetal sheep were randomized to three doses (0.2-4 mg/kg) of iloprost (n = 9) or saline (n = 10), administered as 15-min inhalations with 15-min intervals after a 60-min postnatal stabilization. No differences were found in RVP, arterial PO2, or cardiac index according to treatment. The cerebral oxygenation, measured with near-infrared spectroscopy, deteriorated in control lambs, but not in iloprost lambs. Iloprost treatment followed by iNO resulted in a larger decrease (p = 0.007) in RVP than saline treatment followed by iNO. In conclusion, iloprost stabilized cerebral oxygenation and when followed by iNO had a larger effect on RVP than iNO alone. Although species differences may be relevant, these results suggest that iloprost should be studied in newborn infants for the treatment of PH.