Circulatory changes following premature delivery in a baboon model of hyaline membrane disease

Inhaled nitric oxide in the premature infant: animal models and clinical experience

Inhaled nitric oxide (iNO) is an effective adjuvant therapy for term newborns with persistent pulmonary hypertension. However, its role in treating hypoxemic respiratory failure in premature newborns has not been established. Laboratory experiments have shown the importance of endogenously produced NO in fetal and neonatal pulmonary vasoregulation in the premature lamb. Moreover, low-dose iNO improves oxygenation and reduces pulmonary vascular resistance in the premature lamb with hyaline membrane disease. Preliminary studies have suggested the potential role of low-dose iNO in premature newborns with hyaline membrane disease, sepsis, and pulmonary hypoplasia. However, prematurity poses unique risks that must be carefully addressed with clinical trials designed to measure both safety and efficacy of this promising new therapy.

Recent developments in the pathophysiology and treatment of persistent pulmonary hypertension of the newborn

Successful management of severe PPHN depends on the application of appropriate strategies to manage the cardiopulmonary interactions that characterize this syndrome. Manifestations of PPHN often involve dysfunctional pulmonary vasoregulation, with suprasystemic pulmonary vascular resistance causing extrapulmonary shunting, pulmonary parenchymal disease causing intrapulmonary shunting, and systemic hemodynamic deterioration. Inhaled NO can cause marked improvement in oxygenation when optimal lung inflation is achieved and systemic blood volume and vascular resistance are adequate. Although concern has been expressed regarding potential increases in costs associated with this new therapy, we have found that the successful application of inhaled NO in PPHN has reduced costs of hospitalization and duration of hospital stay by approximately 50% and 40%, respectively. However, inhaled NO alone is unlikely to cause sustained improvement in oxygenation in neonatal hypoxemic respiratory failure associated with severe parenchymal lung disease without extrapulmonary shunting. Inhaled NO may be an important tool in the management of severe PPHN when its application is limited to patients with severe extrapulmonary shunting and vigilant attention is given to changes in the clinical course.