Safety of Withdrawing Inhaled Nitric Oxide Therapy in Persistent Pulmonary Hypertension of the Newborn

Objective. Because of case reports describing hypoxemia on withdrawal of inhaled nitric oxide (I-NO), we prospectively examined this safety issue in newborns with persistent pulmonary hypertension who were classified as treatment successes or failures during a course of I-NO therapy. Methods. Randomized, placebo-controlled, double-masked, dose-response clinical trial at 25 tertiary centers from April 1994 to June 1996. Change in oxygenation and outcome (death and/or extracorporeal membrane oxygenation) during or immediately after withdrawing I-NO were the principal endpoints. Patients (n = 155) were term infants, <3 days old at study entry with echocardiographic evidence of persistent pulmonary hypertension of the newborn. Exclusion criteria included previous surfactant treatment, high-frequency ventilation, or lung hypoplasia. Withdrawal from treatment gas (0, 5, 20, or 80 ppm) started once treatment success or failure criteria were met. Withdrawal of treatment gas occurred at 20% decrements at <4 hours between steps. Results. The patient profile was similar for placebo and I-NO groups. Treatment started at an oxygenation index (OI) of 25 ± 10 (mean ± SD) at 26 ± 18 hours after birth. For infants classified as treatment successes (mean duration of therapy = 88 hours, OI <10), decreases in the arterial partial pressure of oxygen (Pao2) were observed only at the final step of withdrawal. On cessation from 1, 4, and 16 ppm, patients receiving I-NO demonstrated a dose-related reduction in Pao2 (−11 ± 23, −28 ± 24, and −50 ± 48 mm Hg, respectively). For infants classified as treatment failures (mean duration of therapy = 10 hours), no change in OI occurred for the placebo group (−13 ± 36%, OI of 31 ± 11 after the withdrawal process); however a 42 ± 101% increase in OI to 46 ± 21 occurred for the pooled nitric oxide doses. One death was possibly related to withdrawal of I-NO. Conclusion. For infants classified as treatment successes, a dose response between the I-NO dose and decrease in Pao2 after discontinuing I-NO was found. A reduction in I-NO to 1 ppm before discontinuation of the drug seems to minimize the decrease in Pao2 seen. For infants failing treatment, discontinuation of I-NO could pose a life-threatening reduction in oxygenation should extracorporeal membrane oxygenation not be readily available or I-NO cannot be continued on transport.