RESUMO
PURPOSE: Inhaled nitric oxide (iNO) therapy can decrease pulmonary vascular resistance and improve oxygenation through enhanced ventilation-perfusion matching. This study investigated therapeutic response and possible factors affecting the response to iNO in preterm infants with respiratory failure. METHODS: This is a retrospective study of 17 preterm infants with respiratory failure whose birth weight were 1,250 g or less and were treated with iNO, admitted in the neonatal intensive care units at Seoul National University Bundang Hospital between January 2006 and June 2010. Infants were classified as responders if they presented a reduction of FiO2 of more than 20% during 24 hours from the beginning of the treatment, and as non-responder if not. RESULTS: Eight infants (47%) were classified as the responder group and nine infants (53%) as the non-responder group. Mean gestational age was 25.4+/-1.6 weeks in the responder group and 26.0+/-1.6 weeks in the non-responder group. Mean birth weight was 701.9+/-190.1 g in the responder group and 816.1+/-241.6 g in the non-responder group. In the responder group, infants received iNO at postnatal day 12+/-9, in the non-responder group, iNO at postnatal day 35+/-25 (P=0.02). The exposure duration to FiO2 > or =0.5 prior to iNO treatment was significantly shorter in responders than in non-responders (0.1+/-0.4 d vs. 12.6+/-16.3 d, P=0.04). The mechanical ventilation duration was shorter and the postmenstrual age and postnatal age at last extubation were earlier in responders than in non-responders (52+/-25 d vs. 120+/-67 d, P=0.03) (33.1+/-3.0 weeks vs. 45.4+/-9.5 weeks, P=0.01; 55+/-25 d vs. 125+/-59 d, P=0.01). The postmenstrual age and postnatal age at last oxygen treatment were earlier in responders than in non-responders (41.1+/-2.4 weeks vs. 49.0+/-4.5 weeks, P=0.03; 109+/-28 d vs. 158+/-36 d, P=0.03). CONCLUSION: Responders during iNO treatment in preterm infants with respiratory failure had earlier postnatal age and shorter duration of the exposure to hyperoxia. The responder group resulted in good response with early iNO treatment, thus the weaning of mechanical ventilation and oxygen was earlier than the non-responder group. Further studies on effects of beginning time of iNO treatment and long-term effects, especially bronchopulmonary dysplasia, intraventricular hemorrhage and neurodevelopmental outcome are necessary.