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70 patients admitted to the University of Michigan Holden NICU from 21/1/93 through 11/15/96 received inhaled nitric oxide (NO) therapy. 62/70 patients were diagnosed with persistent pulmonary hypertension of the newborn (PPHN) as documented by echocardiogram and/or pre- and postductal PaO2 gradients. 8/70 patients were treated for persistent, intractable hypoxemia thought secondary to intrapulmonary shunt. A positive response was defined as an increase in postductal PaO2 to avoid ECMO. Permanent responders (28/70; 40%) were those who sustained a significant enough increase in postductal PaO2 to avoid ECMO. Transient responders (15/70; 21%) were those who had an initial positive response to inhaled NO, but could not sustain an adequate postductal PaO2, and required ECMO. Non-responders (27/70; 39%) were those who did not respond with an adequate increase in postductal PaO2 to an initial NO test of 40-80 ppm. Non-responders had a mean (+/- SD) baseline PaO2 of 45.6 (+/- 15.3) Torr. Mean baseline PaO2 in transient responders (38.6 +/- 14 Torr) was not significantly different from non-responders (P<0.2). Permanent responders had a significantly higher mean baseline PaO2 (62.6 +/- 25 Torr) over non-responders (P<0.005). Among the permanent responders, there were many more infants (10/28 responders vs. 3/27 non-responders) with radiographically diffuse underlying lung disease(RDS). Infants diagnosed with idiopathic PPHN were represented equally in all groups. Of 8 patients with congenital diaphragmatic hernia, 3 (37%) were responders, 1 (13%) was a transient responder and 4 (50%) were non-responders. There were an equal number of infants with underlying meconium aspiration syndrome and PPHN in both permanent responder and non-responder groups. All 8 infants without documented evidence of PPHN required ECMO. These limited data suggest there is a critical baseline level of oxygenation at or above which patients receiving NO may respond, and certain disease characteristics (e.g. PPHN with underlying diffuse disease) may be important in predicting NO response.

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(Spon by: Roger G. Faix, M.D.)

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