Inhaled nitric oxide by pulmonary hypertension:: Comparison preterm infants versus newborn infants

Background: Inhaled nitric oxide (iNO) is used as a vasodilator in pulmonary hypertension (PH) of the newborn infant. Patients and Methods: Retrospective analysis of patients, who were treated at our department with iNO in the period from 1994-001. Response was defined as an increase of the paO(2)/FiO(2) Ratio greater than or equal to 20% and/or a decrease of the oxygenation index (OI) greater than or equal to 20 % after 2 h (early response), and consecutively after. 24 h (late response). The patients were divided into a) primary persistent pulmonary hypertension of the newborn (PPHN), or b) pulmonary hypertension secondary to meconium aspiration syndrome (MAS), sepsis or congenital diaphragmatic hernia (CDH). Results: Between 1994 and 2001 we treated 47 patients with iNO at our neonatal intensive care unit. We included 16 (35%) preterm infants (GA 34,5 [25-37] weeks, GG 2061 [680-3410]g) (Median/Range) and 31 (65%) newborn (GA40 [38-42] weeks, GG 3510 [2550-4560]g). 18 (38%) patients suffered from primary PPHN, 29 (62%) from secondary PPHN (14 MAS [30%], 8 sepsis [17%], 4 CDH [8%]). 8 (50%) preterm and 20 (64%) term infants showed a positive NO response after 2 h, again 8 (50 %) preterm, and 20 (64%) term infants showed a positive NO response after 24h. There was neither a significant difference between term and preterm infants at 2 h, nor at 24 h. Between 2 h and 24 h 10 patients changed in their response to iNO. 5 (18 %) patients with early response showed a significant degradation after 24h, whereas 5 (26%) of the patients without early response showed a significant improvement of the oxygenation alter 24h. Alltogether 13 (72%) patients with PPHN, 8 (57%) with MAS, 2 (50%) with CDH, 4 (50%) with sepsis showed a positive iNO response after 24h. In regard to the oxygenation parameters at start of iNO-therapy, the patients with early response did not differ from the patient without response (median 01: 20,0 versus 21,8, median paO(2)/FiO(2) Ratio: 59,3 versus 55,0 mmHg at the start of the iNO therapy). Conclusion: In regard to iNO response, there was no significant difference between term and preterm infants. Due to the changing response, a positive iNO-response after 2 h had no predictive value for the further prognosis of the oxygenation situation under iNO therapy.