Rebound Pulmonary Hypertension After Inhalation of Nitric Oxide

Background. We describe the hemodynamic response to initiation and withdrawal of inhaled nitric oxide (NO) in infants with pulmonary hypertension after surgical repair of total anomalous pulmonary venous connection.

Methods. Between January 1, 1992, and January 1, 1995, 20 patients underwent repair of total anomalous pulmonary venous connection. Nine patients had postoperative pulmonary hypertension and received a 15-minute trial of inhaled NO at 80 parts per million. Five of these patients received prolonged treatment with NO at 20 parts per million or less.

Results. Mean pulmonary artery pressure decreased from 35.6 ± 2.4 to 23.7 ± 2.0 mm Hg (mean ± standard error of the mean) (p = 0.008), and pulmonary vascular resistance decreased from 11.5 ± 2.0 to 6.4 ± 1.0 U · m² (p = 0.03). After prolonged treatment with NO, pulmonary artery pressure increased transiently in all patients when NO was discontinued.

Conclusions. After operative repair of total anomalous pulmonary venous connection, inhaled NO selectively vasodilated all patients with pulmonary hypertension. Withdrawal of NO after prolonged inhalation was associated with transient rebound pulmonary hypertension that dissipated within 60 minutes. Appreciation of rebound pulmonary hypertension may have important implications for patients with pulmonary hypertensive disorders when interruption of NO inhalation is necessary or when withdrawal of NO is planned.