Changes in arterial oxygen tension when weaning neonates from inhaled nitric oxide*†

Abstract

We set out to evaluate changes in arterial oxygen tension (PaO(2)) when weaning neonates from inhaled nitric oxide (INO). We reviewed the records of 505 prospectively collected INO weaning attempts on 84 neonates with hypoxic respiratory failure. PaO(2) values before and 30 min after weaning attempts were recorded. Relationships between change in PaO(2) and decreases in INO concentrations were investigated using regression analysis and ANOVA. PaO(2) decreased (-18.7 +/- 1.8 torr; P < 0.001); when weaning INO. A stepwise decline in PaO(2) was observed weaning INO from 40 ppm. The greatest decline occurred when INO was discontinued (-42.1 +/- 4.1 torr). Forward stepwise multiple regression using variables with significant relationships to the decline in PaO(2) identified the specific dose reduction 7(P < 0.001), the prewean PaO(2) (P < 0.001), and surfactant therapy (P = 0.018) as the variables best describing the change in PaO(2)(P = 0.004, r = 0.51). In conclusion, a graded decline in PaO(2) occurs when reducing INO. INO should be weaned to less than 1 ppm before discontinuing its use. Prior surfactant treatment appears to enhance the oxygenation reserve when weaning INO.