Inhaled Nitric Oxide Can Treat Premature Babies with Acute Pulmonary Hypertension, Study Finds

A study finds that, contrary to some reports, the use of inhaled nitric oxide can be effective in treating premature infants with acute pulmonary hypertension.

The study, “The efficacy of inhaled nitric oxide treatment in premature infants with acute pulmonary hypertension,” was published in the journal Early Human Development,

The use of the gas nitric oxide (or inhaled nitric oxide; iNO) in treating babies with acute pulmonary hypertension (PHT) is well-established. It use is largely routine in infants born full-term, or at or after 34 weeks of pregnancy, but its use in those born prematurely is not.

A few studies support the use of iNO in pre-term infants, and it is occasionally used in neonatal units across the world.  But such use remains controversial, and some studies argue against routine use.

Researchers with the neonatal unit at Imperial College Healthcare NHS Trust evaluated the efficacy of iNO treatment in premature infants with acute pulmonary hypertension (PH).

They gathered data on 55 infants born prematurely (less than 34 weeks’ gestation) at London hospitals between 2010 and 2016. All had received iNO for the treatment of acute PH.

The primary outcome of iNO treatment was assessed using FiO2 (or fraction of inspired oxygen). Infants were considered to respond well to iNO if their FiO2 was reduced by 20% or more within three hours of treatment, while those with an FiO2 that increased, was changed or reduced by less than 20%  were regarded as negative responders. The researchers also compared compare neonatal characteristics and outcomes.

Based on the above definitions, the study found that 71% of infants showed a positive response to iNO treatment. Positive responders also had a significantly longer survival rate — 77% — compared to babies who did not respond well to iNO treatment (25%).

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Regarding neonatal characteristics, only oligohydramnios (a deficiency in the amniotic fluid ) and the development of acute pulmonary hypertension within the first three days of life were found to be significantly associated with positive responders. The researchers noted that babies with later acute PH onset also had significantly lower birth weights.

Among the study’s limitations were the relatively small number of infants included, the lack of controls, and its retrospective nature.

Still, its results are encouraging and indicate that “infants below 34 weeks’ gestation, selected appropriately with acute PHT [pulmonary hypertension], show significant proportion of positive response and benefit from iNO administration,” the researchers conclude.

Based on the limitations mentioned above, they add that “further randomized trials would warrant evaluating the impact of iNO administration compared to controls, regarding certain neonatal complications and survival.”