190 - A comparison of two dosing regimens of inhaled nitric oxide in neonates.

Poster Number: 190
Publication Number: 190.2992

Background: Although iNO is widely used to treat hypoxaemic respiratory failure and pulmonary hypertension in neonates, there is little information on optimal dosing regimens. Current recommendations advise starting doses between 5-20 ppm according to gestation.

Objective: We aimed to compare oxygenation response, drug exposure and clinical outcomes between two iNO dosing strategies.

Design/Methods: Retrospective before-and-after observational study in neonates treated with iNO.

In Cohort 1 (2010 to 2013), a ‘low starting dose regimen’ was used where iNO was started at a dose of 5 ppm and titrated up in a stepwise fashion to 20 ppm according to response. There was a change in clinical practice in 2013 because of a perceived delay in achieving an optimal response to starting iNO. In Cohort 2 (2013 to 2016), iNO was started at a higher dose of 20 ppm and weaned according to response. Infants in this cohort were identified to match the sample size in Cohort 1.

We collected information that had been entered prospectively into electronic patient records on demographics, respiratory status, iNO therapy and clinical outcomes. We compared short-term oxygenation response, drug exposure and outcomes including bronchopulmonary dysplasia (BPD) and death in the two cohorts. Oxygenation response was defined as a decrease in oxygenation index of > 20% or more and/or a decrease in FiO2 > 0.2. BPD was defined as a need for any form of respiratory support at 36 weeks’ post-menstrual age.

Results: 158 infants were treated with iNO, approximately 2/3 of whom were preterm < 34 weeks. The most common diagnoses were surfactant-deficient lung disease, perinatal asphyxia and preterm premature rupture of membranes (PPROM)/pulmonary hypoplasia. There were no significant differences in baseline patient characteristics between the two cohorts (Table 1).

Similar proportions of babies were categorised as ‘early responders’ and ‘late responders’ (Table 2). However, exposure to iNO (median dose or duration of therapy) was significantly greater in infants in Cohort 2, the era in which a higher starting dose was used. There were no significant differences in clinical outcomes between the two cohorts (Table 3).

Conclusion(s): We found no differences in response rates or clinical outcomes when comparing a low versus high starting dose regime of iNO therapy. However, the median dose and duration of iNO therapy was greater in the high starting dose era. We conclude that a higher starting dose of iNO may expose neonates to the potential toxic effects of therapy without offering any clinical benefits.