Residual pulmonary hypertension in children after treatment with inhaled nitric oxide: a follow-up study regarding cardiopulmonary and neurological symptoms

Pulmonary hypertension's variegated landscape: a snapshot

The many types of pulmonary hypertension (PH) are so protean in their biological origin, histological expression, and natural history that it is difficult to create a summary picture of the disease, or to easily compare and contrast characteristics of one type of PH with another. For newcomers to the field, however, such a picture would facilitate a broad understanding of PH. In this paper, we suggest that four characteristics are fundamental to describing the nature of various types of PH, and that taken together they define a number of patterns of PH expression. These characteristics are histopathology, developmental origin, associated clinical conditions, and potential for resolution. The “snapshot” is a way to concisely display the ways that these signal characteristics intersect in select specific types of PH, and is an effort to summarize these patterns in a way that facilitates a “big picture” comprehension of this disease.

Treatment of pediatric pulmonary hypertension

Pulmonary hypertension was once thought to be a rare condition and only managed in specialized centers. Now however, with the advent of echocardiography, it is found in many clinical scenarios, in the neonate with chronic lung disease, in the acute setting in the intensive care unit, in connective tissue disease and in cardiology pre- and postoperatively. We have a better understanding of the pathological process and have a range of medication which is starting to be able to palliate this previously fatal condition. This review describes the areas that are known in this condition and those that are less familiar. The basic physiology behind pulmonary hypertension and pulmonary vascular disease is explained. The histopathologic process and the various diagnostic tools are described and are followed by the current and future therapy at our disposal.

Mean airway pressure and response to inhaled nitric oxide in neonatal and pediatric patients

Inhaled nitric oxide (iNO) can improve oxygenation and ventilation-perfusion (V/Q) matching by reduction of shunt (Qs/Qt) in patients with hypoxemic lung disease. Because the improvement in V/Q matching must occur by redistribution of pulmonary blood flow, and because high airway pressure (Paw) increases physiologic dead space (Vd/Vt), we hypothesized that high Paw may limit the improvement in V/Q matching during iNO treatment. iNO 0-50 ppm was administered during mechanical ventilation. Mechanical ventilator settings were at the discretion of the attending physician. Qs/Qt and Vd/Vt were derived from a tripartite lung model with correction for shunt-induced dead space. Data from 62 patients during 153 trials were analyzed for effects of Paw and iNO on Qs/Qt and Vd/Vt. Baseline Qs/Qt was slightly increased at Paw 16-23 cmH2O (p < 0.05), while Vd/Vt increased progressively with higher Paw (p < 0.002). Therapy with iNO significantly reduced Qs/Qt (p < 0.001) at all levels of mean Paw, reaching a maximum reduction at 16-23 cmH2O (p < 0.05), such that Qs/Qt during iNO treatment was similar at all levels of Paw. During iNO treatment, a reduction in Vd/Vt occurred only at Paw of 8-15 cmH2O (p < 0.05), and the positive relationship between Vd/Vt and Paw was maintained. These differential effects on Qs/Qt and Vd/Vt suggest that both high and low Paw may limit improvement in gas exchange with iNO. Analysis of gas exchange using this corrected tripartite lung model may help optimize ventilatory strategies during iNO therapy.

Three-year follow up of term and near-term infants treated with inhaled nitric oxide

BACKGROUND

The present study describes the outcome at 3 years in term and near-term infants treated with inhaled nitric oxide (iNO) for persistent pulmonary hypertension of the newborn (PPHN).

METHODS

The study population consisted of 18 infants delivered at 34 weeks by best obstetric estimate who were admitted to the neonatal intensive care units with a diagnosis of PPHN.

RESULTS

Eighteen infants (mean gestational age 38.5 +/- 2.6 weeks, mean birthweight 3015 +/- 587 g) were treated with iNO. The mean oxygenation index before iNO was 27.2 +/- 15.2. Responses to iNO were classified into three groups: (i) early response in eight infants; (ii) late response in two; and (iii) poor response in eight infants. Three infants died within seven postnatal days. Fifteen surviving infants were followed up to 3 years. The mean developmental scale was 98.4 +/- 9.0. One infant was diagnosed with severe neurodevelopmental disability due to cerebral palsy. Another infant was diagnosed with mild neurodevelopmental disability because of a low developmental scale. No infant showed significant hearing loss. Five infants had reactive airway disease (RAD) at 18 months, these infants required a significantly longer duration of mechanical ventilation in their neonatal period than non-RAD infants (P = 0.02). The frequency of survival with normal neurodevelopmental outcome was significantly higher in the early response group than the late or poor response groups (P = 0.03).

CONCLUSION

In iNO-treated PPHN, mortality and neurodevelopmental outcome were associated with response to iNO, and pulmonary outcome was associated with duration of mechanical ventilation.