Pulmonary prostacyclin is associated with less severe respiratory distress in preterm infants.

Background: Prostacyclin (PGI2) and thromboxane A2 (TxA2) may take part in lung pathology; high concentrations of PGI2 may protect newborn rabbits against hyperoxic lung injury, and TxA2 may participate in the development of bronchopulmonary dysplasia (BPD). Aims: To examine in small preterm infants, the relationship between pulmonary PGI2 and TxA2 and respiratory distress during the early postnatal period. Methods: The stable metabolite of prostacyclin, 6-keto-prostaglandinF1alpha, and that of thromboxane A2, thromboxane B2, were quantified by radioimmunoassays in 284 samples of tracheal aspirates from 48 infants (GA: 27.4±2.1 week, BW 959±334 g) during the first 12 postnatal days. Results: Mean concentration of 6-keto-prostaglandinF1alpha was 414±31 pg/ml (mean±S.E.M.), and of thromboxane B2 was 418±37 pg/ml. Correlations existed between 6-keto-prostaglandinF1alpha and gestational age, birth weight, and the initial arterial–alveolar oxygenation ratio. Negative correlations existed between 6-keto-prostaglandinF1alpha and both mean inspiratory oxygen and duration of mechanical ventilation. Indomethacin treatment was associated with lower pulmonary 6-keto-prostaglandinF1alpha, but not with lower TxB2. Thromboxane B2 correlated positively with gestational age, birth weight, and initial arterial–alveolar oxygenation ratio, and inversely with duration of mechanical ventilation. Conclusions: In preterm infants, higher pulmonary 6-keto-prostaglandinF1alpha was associated with less severe respiratory distress and with maturity, whereas thromboxane B2 was associated more strongly with maturity than with respiratory distress.