Persistent pulmonary hypertension of the neonate and asymmetric growth restriction

Pulmonary hypertension in preterm infants: prevalence and association with bronchopulmonary dysplasia

OBJECTIVE

To determine whether early pulmonary hypertension (PH) at 10-14 days of life in preterm infants is associated with bronchopulmonary dysplasia (BPD) at 36 weeks' postmenstrual age (PMA).

STUDY DESIGN

This was a prospective observational cohort study of infants <28 weeks' gestation. Exclusion criteria were any major anomaly, genetic syndrome, or death before the initial echocardiogram. Echocardiograms were performed between 10 and 14 days of life and at 36 weeks' PMA to assess PH. BPD and its severity were determined at 36 weeks PMA by the National Institutes of Health workshop definition.

RESULTS

From March 2011 to April 2013, of 146 consecutively admitted infants <28 weeks, 120 were enrolled. One infant was excluded, 17 did not consent, and 8 died before undergoing a study echocardiogram. At 10-14 days of life, 10 infants had early PH (8%). Male sex (56% vs 40%), gestational age (26(+2) ± 1(+2) vs 25(+6) ± 1(+4) weeks), birth weight (837 ± 205 g vs 763 ± 182 g), and small for gestational age (14% vs 20%) were not significantly different among infants with no PH and early PH, respectively. Infants with early PH required >0.3 fraction of inspired oxygen by day 10 of life (70% vs 27%, P < .01). Moderate/severe BPD or death was greater among infants with early PH (90%) compared with no PH (47%, relative risk 1.9, 95% CI 1.43-2.53).

CONCLUSION

In this prospective, single-center cohort, early PH was associated with moderate/severe BPD or death at 36 weeks' PMA.

The Robyn Barst Memorial Lecture: Differences between the fetal, newborn, and adult pulmonary circulations: relevance for age-specific therapies (2013 Grover Conference series)

Pulmonary arterial hypertension (PAH) contributes to poor outcomes in diverse diseases in newborns, infants, and children. Many aspects of pediatric PAH parallel the pathophysiology and disease courses observed in adult patients; however, critical maturational differences exist that contribute to distinct outcomes and therapeutic responses in children. In comparison with adult PAH, disruption of lung vascular growth and development, or angiogenesis, plays an especially prominent role in the pathobiology of pediatric PAH. In children, abnormalities of lung vascular development have consequences well beyond the adverse hemodynamic effects of PAH alone. The developing endothelium also plays critical roles in development of the distal airspace, establishing lung surface area for gas exchange and maintenance of lung structure throughout postnatal life through angiocrine signaling. Impaired functional and structural adaptations of the pulmonary circulation during the transition from fetal to postnatal life contribute significantly to poor outcomes in such disorders as persistent pulmonary hypertension of the newborn, congenital diaphragmatic hernia, bronchopulmonary dysplasia, Down syndrome, and forms of congenital heart disease. In addition, several studies support the hypothesis that early perinatal events that alter lung vascular growth or function may set the stage for increased susceptibility to PAH in adult patients ("fetal programming"). Thus, insights into basic mechanisms underlying unique features of the developing pulmonary circulation, especially as related to preservation of endothelial survival and function, may provide unique therapeutic windows and distinct strategies to improve short- and long-term outcomes of children with PAH.

Long term respiratory consequences of intrauterine growth restriction

Epidemiological studies demonstrate that in-utero growth restriction and low birth weight are associated with impaired lung function and increased respiratory morbidity from infancy, throughout childhood and into adulthood. Chronic restriction of nutrients and/or oxygen during late pregnancy causes abnormalities in the airways and lungs of offspring, including smaller numbers of enlarged alveoli with thicker septal walls and basement membranes. The structural abnormalities and impaired lung function seen soon after birth persist or even progress with age. These changes are likely to cause lung symptomology through life and hasten lung aging.

Current concepts in intrauterine growth restriction

Regulation of fetal growth is multifactorial and complex. Diverse factors, including intrinsic fetal conditions as well as maternal and environmental factors, can lead to intrauterine growth restriction (IUGR). The interaction of these factors governs the partitioning of nutrients and rate of fetal cellular proliferation and maturation. Although IUGR is probably a physiologic adaptive response to various stimuli, it is associated with distinct short- and long-term morbidities. Immediate morbidities include those associated with prematurity and inadequate nutrient reserve, while childhood morbidities relate to impaired maturation and disrupted organ development. Potential long-term effects of IUGR are debated and explained by the fetal programming hypothesis. In formulating a comprehensive approach to the management and follow-up of the growth-restricted fetus and infant, physicians should take into consideration the etiology, timing, and severity of IUGR. In addition, they should be cognizant of the immediate perinatal response of the growth-restricted infant as well as the childhood and long-term associated morbidities. A multi disciplinary approach is imperative, including early recognition and obstetrical management of IUGR, assessment of the growth-restricted newborn in the delivery room, possible monitoring in the neonatal intensive care unit, and appropriate pediatric follow-up. Future research is necessary to establish effective preventive, diagnostic, and therapeutic strategies for IUGR, perhaps affecting the health of future generations.