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Nitric Oxide

by Mary E. Wearden, MD

Nitric oxide has been approved by the FDA for treatment of pulmonary hypertension in newborns 34 weeks’ gestation and greater. FDA approval was based on the results of several large, randomized, controlled trials that demonstrated that the use of inhaled nitric oxide in newborns with hypoxemic respiratory failure improves oxygenation and reduces the need for ECMO or heart-lung bypass by 40%. The Newborn Section at Baylor College of Medicine participated in the first large trial and treats more than 30 infants a year with inhaled nitric oxide.

Nitric oxide is a ubiquitous molecule with vasodilator and cell signalling capabilities. Inhaled nitric oxide is a freely diffusible gas that is a pulmonary vasodilator in newborns with hypoxemic respiratory failure as a consequence of or in association with pulmonary hypertension. The conditions associated with pulmonary hypertension include primary pulmonary hypertension, meconium aspiration, pneumonia, sepsis, and pulmonary hypoplasia. An estimated 3000 infants per year will be treated with inhaled nitric oxide.

Before nitric oxide was available, treatment for pulmonary hypertension included oxygen, mechanical ventilation, alkalinization, and extracorporeal membrane oxygenation (ECMO). ECMO is labor-intensive, exposes the infants to large amounts of blood products, frequently requires ligation of the carotid artery, and creates potential for hemorrhage because of the heparinization required. In contrast, nitric oxide has been demonstrated to be safe and efficacious. The gas is delivered through the ventilator circuit, so it is easy to administer.

Nitric oxide appears to be safe, and developmental outcomes are comparable to those achieved with ECMO without the need to perform invasive surgery. However, immediate accessibility to an ECMO center must be considered when using nitric oxide treatment.

Future studies and uses of inhaled nitric oxide will include use in premature infants and infants with pulmonary hypertension associated with congenital heart disease. Meanwhile, inhaled nitric oxide will become part of our standard armamentarium in the treatment of pulmonary hypertension.