Response to Inhaled Nitric Oxide and Clinical Outcome in Very Low Birth Weight Infants with Early Pulmonary Hypertension

Abstract

Purpose: To determine the efficacy of inhaled nitric oxide (iNO) in very low birth weight (VLBW) infants with early pulmonary hypertension (PH). Methods: We reviewed the medical records of 22 preterm infants who were born <30 weeks of gestational age with birth weight <1,500 g, diagnosed with early PH, and treated with iNO within the first 72 hours after birth. Responders were defined by a reduction in FiO2 >20% and/or oxygenation index (OI) >20% from the baseline values at 1 hour after beginning iNO therapy. Cardiorespiratory support indices including OI, oxygen saturation index, and vasoactive-inotropic score (VIS) were serially obtained for 96 hours following iNO therapy. Results: The mean gestational age of the patients was 26.1±2.0 weeks and the mean birth weight was 842±298 g. The mean OI at the start of iNO was 63.8±61.0. Improvement in oxygenation indicated by prompt decrease in FiO2 and OI from the baseline values were observed 1 hour after beginning iNO therapy and lasted up to 96 hours. After iNO therapy, VIS increased until 24 hours and decreased thereafter. At 1 hour after iNO, 16 patients (73%) were classified as responders and six (27%) as nonresponders. Compared with nonresponders, responders did not demonstrate the beneficial effect of iNO in terms of short-term survival and neonatal complications. The 1-year mortality rate did not differ between responders (56%) and nonresponders (67%). Conclusion: Although iNO treatment immediately improved oxygenation in most VLBW infants with early severe PH, the long-term mortality rate was high. A largescale study is needed to determine whether the initial response to iNO can predict patients’ survival.