Neonatal-perinatal risk factors for the development of persistent pulmonary hypertension of the newborn in preterm newborns

Sudden Onset of Severe Pulmonary Hypertension in a Preterm Infant: A Case Report on the Role of Maternal Use of Serotonin Re-Uptake Inhibitors During Pregnancy and Concurrent Risk Factors

Persistent pulmonary hypertension of the newborn (PPHN) is a severe condition caused by failed circulatory adaptation at birth. Pulmonary hypertension is most common in full-term infants and rare in preterms, although it is increasingly diagnosed also in extremely preterm infants. Previous studies demonstrated the association between maternal use of selective serotonin re-uptake inhibitors during gestation and pulmonary hypertension. This brief report describes the complex physiopathological correlations that were identified in a case of severe pulmonary hypertension in a fetal growth restricted (FGR) preterm infant, with a history of maternal use of antidepressants during pregnancy. Perinatal factors, triggers and aggravating mechanisms caused a dramatic clinical course. Maternal history of escitalopram therapy throughout pregnancy was noted. Uteroplacental insufficiency, fetal hypoxia, FGR, preeclampsia, preterm delivery, antenatal steroids, and cesarean section were documented as concurrent risk factors. Myocardial immaturity and dysfunction, secondary to FGR and prematurity aggravated the hemodynamic compromise. The short time gap between pharmacological ductal closure and the onset of PPHN may suggest a cause-effect relationship, as observed in previous reports. Placental histopathologic findings are reported.

A Meta-Analysis of the Risk Factors of Persistent Pulmonary Hypertension in Newborns

Objective: To determine the risk factors of persistent pulmonary hypertension of the newborn using a meta-analysis method and provide a reference for its clinical prevention and treatment. Methods: A meta-analysis was performed by searching the PubMed, Embase, Cochrane Library, China Biology Medicine Disc, Wanfang, and Chinese VIP journal databases, as well as the China National Knowledge Infrastructure. Results: A total of 22 references were included in the meta-analysis; the cumulative medical records comprised 7,937 cases, and 2,613,072 control cases were included. A total of 12 related risk factors were included (7 were associated with pregnant women and 5 were associated with newborns). Conclusion: Among the 12 associated risk factors included, the three most important and their combined odds ratio values and 95% CI were as follows: (1) pregnant women smoking, 4.85 (1.98-11.9) during pregnancy; (2) gestational weeks <37, 4.34 (1.64-11.5); (3) perinatal asphyxia, 3.9 (2.87-5.31).

Pediatric Pulmonary Hypertension: Definitions, Mechanisms, Diagnosis, and Treatment

Pediatric pulmonary hypertension (PPH) is a multifactorial disease with diverse etiologies and presenting features. Pulmonary hypertension (PH), defined as elevated pulmonary artery pressure, is the presenting feature for several pulmonary vascular diseases. It is often a hidden component of other lung diseases, such as cystic fibrosis and bronchopulmonary dysplasia. Alterations in lung development and genetic conditions are an important contributor to pediatric pulmonary hypertensive disease, which is a distinct entity from adult PH. Many of the causes of pediatric PH have prenatal onset with altered lung development due to maternal and fetal conditions. Since lung growth is altered in several conditions that lead to PPH, therapy for PPH includes both pulmonary vasodilators and strategies to restore lung growth. These strategies include optimal alveolar recruitment, maintaining physiologic blood gas tension, nutritional support, and addressing contributing factors, such as airway disease and gastroesophageal reflux. The outcome for infants and children with PH is highly variable and largely dependent on the underlying cause. The best outcomes are for neonates with persistent pulmonary hypertension (PPHN) and reversible lung diseases, while some genetic conditions such as alveolar capillary dysplasia are lethal. © 2021 American Physiological Society. Compr Physiol 11:2135-2190, 2021.

Risk factors and outcomes of early pulmonary hypertension in preterm infants

PURPOSE

Data on early pulmonary arterial hypertension (PAH) in preterm infants is limited and outcomes are conflicting. Our objectives are to examine the risk factors and neonatal outcomes of early onset PAH (EOPAH) diagnosed in the first 2 weeks of age in preterm infants in a large perinatal center.

METHODS

We performed a case-control study to assess the risk factors and clinical outcomes of preterm infants with EOPAH. Preterm infants (<34 weeks) admitted to NICU between 2009 and 2013 with a diagnosis of PAH in the first 2 weeks of age were matched to two consecutive controls for gestational age, birth weight, and year of birth. We performed univariate and multivariate analyses.

RESULTS

Of 1798 eligible infants, 60 (3.3%) had EOPAH with 57/60 (95%) diagnosed in the first 7 d of age. Infants with early PAH had higher incidence of prolonged rupture of membrane (47% versus 29%), oligohydramnios (37% versus 16%) and received less antenatal steroids (78% versus 91%). Fifty-one infants received inhaled nitric oxide (iNO) and all responded well. The overall mortality rate was not significantly different between two groups (13.3% versus 8%). After adjusting for potential confounding variables, early PAH is associated with bronchopulmonary dysplasia (BPD) (aOR 3.06, 95% CI 1.43, 6.54) and BPD/death (aOR 2.65, 95% CI 1.25, 5.64) and severe intraventricular hemorrhage (aOR 3.08, 95% CI 1.28, 7.39).

CONCLUSION

Early onset pulmonary arterial hypertension in preterm is not uncommon and is associated with bronchopulmonary dysplasia and severe intraventricular hemorrhage. Inhaled nitric oxide was used to treat in majority of cases with good response and survival is high.

Persistent Pulmonary Hypertension of the Newborn in Twin-Twin Transfusion Syndrome: A Case-Control Study

BACKGROUND

Persistent pulmonary hypertension of the newborn (PPHN) is associated with severe morbidity and mortality. Twin-twin transfusion syndrome (TTTS) is suggested to increase the risk of PPHN.

OBJECTIVES

To describe the incidence of PPHN in TTTS twins and to identify risk factors in TTTS twins for the development of severe PPHN.

METHODS

Cases with severe PPHN were extracted from our monochorionic twin database (2002-2016). Severe PPHN was defined as severe hypoxaemia requiring mechanical ventilation and inhaled nitric oxide (iNO) treatment, confirmed by strict echocardiographic criteria. A case-control comparison within TTTS survivors was conducted to identify risk factors for PPHN.

RESULTS

The incidence of PPHN in TTTS twins was 4% (24/598, 95% confidence interval [CI] 2.7-5.9%) and 0.4% (2/493, 95% CI 0.1-1.5%) in uncomplicated monochorionic twins (odds ratio [OR] 10.3, 95% CI 2.4-43.9; p = 0.002). Two risk factors were independently associated with PPHN: severe prematurity (OR 3.3, 95% CI 1.0-11.4) and recipient status (OR 3.9, 95% CI 1.4-11.0). In TTTS recipients, another risk factor for PPHN is anaemia at birth (OR 7.2, 95% CI 1.8-29.6).

CONCLUSION

Clinicians caring for neonates with TTTS should be aware of the 10-fold increased risk of PPHN compared to uncomplicated monochorionic twins. PPHN occurs more often in case of premature delivery and in recipient twins, particularly in the presence of anaemia at birth. As the development of severe PPHN is difficult to predict, we advise that all TTTS twins should be delivered in a tertiary care centre with iNO treatment options.

Adverse perinatal and neonatal outcomes in patients with chronic abruption-oligohydramnios sequence

AIM

Chronic abruption-oligohydramnios sequence (CAOS) is a clinical condition with lasting vaginal bleeding and oligohydramnios because of chronic placental abruption, which seems to cause preterm labor and neonatal chronic lung disease (CLD). This prompted us to explore the correlation between perinatal/neonatal outcomes and CAOS.

METHODS

Patients with suspected risk of abortion with recurrent vaginal bleeding were divided into CAOS and non-CAOS groups, and we compared the perinatal/neonatal outcomes between these two groups. To examine the impact of chorioamnionitis (CAM) on the prognosis of CAOS, we also compared outcomes between the CAOS group and gestational-age-matched preterm labor due to CAM (CAM group).

RESULTS

In the CAOS and non-CAOS groups, initial vaginal bleeding was seen at the first trimester. However, its duration was significantly longer in the CAOS group. Additionally, neonatal birthweight was lower, and small-for-gestational-age (SGA) incidence was higher in the CAOS group. CLD was observed in most infants from CAOS patients. In the comparison between CAOS and CAM groups, birthweight was lower and SGA incidence was higher in the CAOS group. Moreover, CLD incidence and neonatal mortality were significantly higher, despite the lower incidence of severe CAM in the CAOS group. Finally, multivariate analysis demonstrated that duration of bleeding was a significant predictive factor for CAOS.

CONCLUSIONS

Our observations demonstrated that patients with CAOS were a high-risk group for poor perinatal/neonatal outcomes. Moreover, episodes of recurrent and prolonged uterine bleeding were predictive factors for CAOS. During the first trimester, prolonged bleeding is an important sign as one symptom of CAOS.

Pathophysiology of persistent pulmonary hypertension of the newborn: impact of the perinatal environment

The main cause of pulmonary hypertension in newborn babies results from the failure of the pulmonary circulation to dilate at birth, termed 'persistent pulmonary hypertension of the newborn' (PPHN). This syndrome is characterized by sustained elevation of pulmonary vascular resistance, causing extrapulmonary right-to-left shunting of blood across the ductus arteriosus and foramen ovale and severe hypoxaemia. It can also lead to life-threatening circulatory failure. There are many controversial and unresolved issues regarding the pathophysiology of PPHN, and these are discussed. PPHN is generally associated with factors such as congenital diaphragmatic hernia, birth asphyxia, sepsis, meconium aspiration and respiratory distress syndrome. However, the perinatal environment-exposure to nicotine and certain medications, maternal obesity and diabetes, epigenetics, painful stimuli and birth by Caesarean section-may also affect the maladaptation of the lung circulation at birth. In infants with PPHN, it is important to optimize circulatory function. Suggested management strategies for PPHN include: avoidance of environmental factors that worsen PPHN (e.g. noxious stimuli, lung overdistension); adequate lung recruitment and alveolar ventilation; inhaled nitric oxide (or sildenafil, if inhaled nitric oxide is not available); haemodynamic assessment; appropriate fluid and cardiovascular resuscitation and inotropic and vasoactive agents.

Effects of environmental tobacco smoke on the pulmonary circulation in the ovine fetus

OBJECTIVE

Epidemiologic studies have highlighted an association between maternal smoking and persistent pulmonary hypertension of the newborn infant. However, the impact of exposure to tobacco smoke on the perinatal pulmonary circulation is currently unknown. The purpose of this study was to assess the pulmonary vascular effects of environmental tobacco smoke in the fetus.

STUDY DESIGN

We performed surgery on 16 fetal lambs and placed catheters in the main pulmonary artery, aorta, and left atrium to measure pressures. An ultrasonic blood flow transducer was placed around the left pulmonary artery to measure blood flow. The ewes were exposed to tobacco smoke for 2 hours. In another set of experiments, the pulmonary vascular response to increased fetal O(2) tension has been assessed after 2 hours of tobacco smoke inhalation or not (control group).

RESULTS

Exposure to tobacco smoke decreased pulmonary blood flow by 30% and elevated pulmonary vascular resistance by 40%. The vasodilator response to increased O(2) tension was blunted after smoke inhalation compared with control animals. Smoke inhalation was associated with a decrease in fetal PaO(2) and SaO(2).

CONCLUSION

Exposure to environmental tobacco smoke in pregnant ewes impairs both basal tone and vascular reactivity of the fetal lung.

Current and future therapeutic options for persistent pulmonary hypertension in the newborn

Persistent pulmonary hypertension of the newborn (PPHN) is a potentially life-threatening condition that is characterized by supra-systemic pulmonary vascular resistance causing right-to-left shunting through the ductus arteriosus and/or foramen ovale, leading to a vicious cycle of hypoxemia, acidosis and further pulmonary vasoconstriction. Advances in neonatology including surfactant instillation, high-frequency ventilation, extracorporeal membrane oxygenation and, most importantly, inhaled nitric oxide (INO), have revolutionized the management of PPHN. However, given that INO does not improve oxygenation in a significant proportion (30-40%) of cases, there is an urgent need to consider other therapeutic options for PPHN. The issue is more important for developing nations with a higher PPHN-related health burden and limited resources. This article discusses the evidence about INO in term and preterm neonates in brief, and focuses mainly on the potential alternative drugs in the management of PPHN.

Risk of persistent pulmonary hypertension of the neonate in twin-to-twin transfusion syndrome

BACKGROUND

Chronic twin-to-twin transfusion syndrome (TTTS) is a complication of monochorionic twin gestations and is associated with high perinatal mortality and increased neurological, cardiovascular and renal morbidity.

OBJECTIVE

To report the risk of severe persistent pulmonary hypertension of the newborn (PPHN) in TTTS and discuss the possible association between severe PPHN and TTTS.

METHODS

All cases of monochorionic twins with severe PPHN at birth admitted to our nursery between June 2002 and July 2006 were reviewed retrospectively. We compared the incidence of severe PPHN in monochorionic twins with and without TTTS. Severe PPHN was diagnosed according to clinical and ultrasound criteria when an infant with a structurally normal heart had (1) severe hypoxemia and (2) evidence of a right-to-left shunt on persistent ductus arteriosus or foramen ovale, requiring treatment with inhaled nitric oxide (iNO).

RESULTS

In a consecutive series of 73 twin pregnancies with TTTS, 4 of the 135 live-born twins (3%) were affected by severe PPHN. All reacted promptly to treatment with iNO. The incidence of severe PPHN in monochorionic twins without TTTS was 0% (0/161).

CONCLUSION

In view of the severe clinical course in PPHN and need for adequate and prompt treatment with iNO, perinatologists should be aware of the increased risk of severe PPHN in TTTS.

Maternal, neonatal, and placental features associated with diffuse chorioamniotic hemosiderosis, with special reference to neonatal morbidity and mortality

OBJECTIVE

Our purpose was to examine the significance of diffuse chorioamniotic hemosiderosis (DCH) on neonatal morbidity and mortality.

METHODS

Using data from a retrospective case-control study, we analyzed 46 singleton placentas with DCH from infants who were delivered and/or admitted to the neonatal intensive care unit of Kanagawa Children's Medical Center during 1987-2001 and 92 control placentas without DCH from infants of comparable gestational age, birth weight, and duration.

RESULTS

Mean and standard deviation of gestational age and infants' birth weight at delivery from the DCH group were 27 +/- 3 weeks and 939 +/- 342 g, respectively. Macroscopically, the placentas with DCH were more likely to show old peripheral blood clots (46% in the DCH group vs 8% in control group), subchorionic hematoma (20% vs 1%), and circumvallation (13% vs 1%). Histologically, amniotic necrosis was significantly more frequent in the DCH group (63% vs 24%). Of the obstetric factors, incidence of recurrent episodes of vaginal bleeding (70% vs 11%), oligohydramnios (59% vs 8%), and chronic abruption-oligohydramnios sequence (57% vs 5%) were significantly higher in the DCH group. Of the neonatal factors, persistent pulmonary hypertension of the newborn (29% vs 8%) and dry lung and/or pulmonary hypoplasia (20% vs 4%) were more common. However, respiratory distress syndrome was rare (15% vs 45%) in the DCH group. Neonatal death including stillbirth was increased in the DCH group but was not significant (24% vs 15%). Of infants who survived beyond day 28, chronic lung disease (CLD) was more frequent in the DCH group (51% vs 22%). The association of DCH, especially accompanied by amniotic necrosis, with CLD was still evident using likelihood ratio test.

CONCLUSION

DCH is closely associated with preterm delivery, pulmonary hypertension of the newborn, and dry lung syndrome and is a significant risk factor for CLD.