4 PATTERNS OF RESPONSE TO INHALED NITRIC-OXIDE FOR PERSISTENT PULMONARY-HYPERTENSION OF THE NEWBORN

Objective. To determine the clinical role of inhaled nitric oxide (iNO ) in the treatment of persistent pulmonary hypertension of the newborn (PPHN). Study Design. Prospective open observational clinical study. Setting. A regional cardiac and pediatric intensive care unit. Methods . Twenty-five consecutive near-term neonates (>35 weeks gestation) wit h severe FPHN (oxygenation index [OI] >25) were given a trial of iNO o f 20 ppm for 20 minutes. Neonates who showed a greater than 20% improv ement in Pa-O2 as well as a decrease in the OI to below 40 were define d as responders and continued on this therapy. Results. Four patterns of response emerged to the iNO therapy: Pattern 1 neonates (n = 2) did not respond to the initial trial of iNO--one survived. Pattern 2 neon ates (n = 9) responded to the initial trial of iNO, but failed to sust ain this response over 36 hours, as defined by a rise in the OI to >40 . Six survived, five with extracorporeal membrane oxygenation. Pattern 3 neonates (n = 11) responded to the initial trial of iNO, sustained this response, and were successfully weaned from iNO within 5 days--al l survived to discharge. Pattern 4 neonates (n = 3) responded to the i nitial trial of iNO, but developed a sustained dependence on iNO for 3 to 6 weeks. All three died and lung histology revealed severe pulmona ry hypoplasia and dysplasia. These neonates (pattern 4) not only requi red iNO for a longer period of time than did the sustained responders (pattern 3), but they required significantly higher doses of iNO durin g their first 5 days of iNO therapy. Conclusions. Early responses to i NO may not be sustained. Neonates with pulmonary hypoplasia and dyspla sia may have a decreased sensitivity and differing time course of resp onse to iNO when compared with patients who have PPHN in fully develop ed lungs.