Objective To describe short-term and long-term outcomes of preterm neonates with severe acute pulmonary hypertension (aPHT) in relation to response to rescue inhaled nitric oxide (iNO) therapy.

Design Retrospective cohort studyover a 6 year period.

Setting Tertiary neonatal intensive care unit.

Patients 89 neonates <35 weeks gestational age (GA) who received rescue iNO for aPHT, including 62 treated at ≤3 days of age (early aPHT).

Interventions iNO ≥ 1 hour.

Main outcome measures Positive responders (reduction in fraction of inspired oxygen (FiO₂) ≥0.20 within 1 hour of iNO) were compared with non-responders. Primary outcome was survival without moderate-to-severe disability at 18 months of age.

Results Mean (SD) GA and birth weight was 27.7 (3.0) weeks and 1077 (473) gm, respectively. Median (IQR) pre-iNO FiO₂ was 1.0 (1.0, 1.0). Positive response rate to iNO was 46%. Responders showed improved survival without disability (51% vs 15%; p<0.01), lower mortality (34% vs 71%; p<0.01) and disability among survivors (17% vs 50%; p=0.06). Higher GA (adjusted OR: 1.44 (95% CI 1.10 to 1.89)), aPHT in context of preterm prolonged rupture of membranes (6.26 (95% CI 1.44 to 27.20)) and positive response to rescue iNO (5.81 (95% CI 1.29 to, 26.18)) were independently associated with the primary outcome. Compared with late cases (>3 days of age), early aPHT had a higher response rate to iNO (61% vs 11%; p<0.01) and lower mortality (43% vs 78%; p<0.01).

Conclusion A positive response to rescue iNO in preterm infants with aPHT is associated with survival benefit, which is not offset by long-term disability.