Defective pulmonary innervation and autonomic imbalance in congenital diaphragmatic hernia

Diagnosis, management and long term cardiovascular outcomes of phenotypic profiles in pulmonary hypertension associated with congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a developmental defect of the diaphragm resulting in herniation of viscera into the chest. This condition is characterized by pulmonary hypoplasia, pulmonary hypertension (PH) and cardiac ventricular dysfunction. PH is a key component of the pathophysiology of CDH in neonates and contributes to morbidity and mortality. Traditionally, PH associated with CDH (CDH-PH) is thought to be secondary to increased pulmonary arterial resistance and vasoreactivity resulting from pulmonary hypoplasia. Additionally, there is increasing recognition of associated left ventricular hypoplasia, dysfunction and elevated end diastolic pressure resulting in pulmonary venous hypertension in infants with CDH. Thus, hemodynamic management of these infants is complex and cautious use of pulmonary vasodilators such as inhaled nitric oxide (iNO) is warranted. We aim to provide an overview of different phenotypic profiles of CDH associated PH and potential management options based on current evidence and pathophysiology.

Congenital diaphragmatic hernia with associated broncho-pulmonary sequestration: A report of two cases and a literature review

BACKGROUND

Congenital Diaphragmatic Hernia (CDH) is a severe congenital anomaly with significant morbidity and mortality. It can be isolated or can be associated with other congenital anomalies, including broncho-pulmonary sequestration (BPS). The association of CDH with BPS (CDH+BPS) is uncommon but has been previously reported, and it can complicate the course of the disease in patients with CDH. We report two cases of CDH+BPS that were recently treated at our CDH-Qatar (CDH-Q) program.

METHODS

We reviewed CDH-Q program registry to search for CDH+BPS and extracted the data for the identified cases. We also reviewed the previously published literature available on PubMed for similar cases.

RESULTS

Out of 53 cases of CDH referred to CDH-Q from January 2018 to December 2022, two cases of CDH+BPS were identified, with an estimated prevalence of 3.8% of this association in our CDH population. Both cases were born at term. Case 1 was diagnosed with CDH+BPS postnatally, while case 2 was diagnosed with CDH antenatally but BPS was diagnosed after birth. Both cases underwent a surgical repair of the CDH with resection of the associated BPS, and the histopathology of the resected lung tissue confirmed the presence of BPS in both. Both cases survived to discharge.

CONCLUSION

The association of CDH+BPS is uncommon; however, it can have significant consequences on the management and the prognosis of patients with CDH. Reporting these cases is important to provide a better understanding of this association and its impact on CDH patients.

Intact cord resuscitation in newborns with congenital diaphragmatic hernia: insights from a lamb model

Introduction

Congenital diaphragmatic hernia (CDH) is a rare condition characterized by pulmonary hypoplasia, vascular dystrophy, and pulmonary hypertension at birth. Validation of the lamb model as an accurate representation of human CDH is essential to translating research findings into clinical practice and understanding disease mechanisms. This article emphasizes the importance of validating the lamb model to study CDH pathogenesis and develop innovative therapeutics.

Material and methods

At 78 days of gestation, the fetal lamb's left forelimb was exposed through a midline laparotomy and hysterotomy, and a supra diaphragmatic thoracotomy was performed to allow the digestive organs to ascend into the thoracic cavity. At 138 ± 3 days of gestation, lambs were delivered via a cesarean section; then, with umbilical cord intact during 1 hour, the lambs were mechanically ventilated with gentle ventilation in a pressure-controlled mode for 2 h.

Results

CDH lambs exhibited a lower left lung-to-body weight ratio of 5.3 (2.03), p < 0.05, and right lung-to-body weight ratio of 8.2 (3.1), p < 0.05. They reached lower Vt/kg (tidal volume per kg) during the course of the resuscitation period with 1.2 (0.7) ml/kg at 10 min and 3 (1.65) ml/kg at 60 min (p < 0.05). Compliance of the respiratory system was lower in CDH lambs with 0.5 (0.3) ml/cmH2O at 60 min (p < 0.05) and 0.9 (0.26) ml/cmH2O at 120 min (p < 0.05). Differences between pre- and postductal SpO2 were higher with 15.1% (21.4%) at 20 min and 6.7% (14.5%) at 80 min (p < 0.05). CDH lambs had lower differences between inspired and expired oxygen fractions with 4.55% (6.84%) at 20 min and 6.72% (8.57%) at 60 min (p < 0.05). CDH lamb had lower left ventricle [2.73 (0.5) g/kg, p < 0.05] and lower right ventricle [0.69 (0.8), p < 0.05] to left ventricle ratio.

Discussion

CDH lambs had significantly lower tidal volume than control lambs due to lower compliance of the respiratory system and higher airway resistance. These respiratory changes are characteristic of CDH infants and are associated with higher mortality rates. CDH lambs also exhibited pulmonary hypertension, pulmonary hypoplasia, and left ventricle hypoplasia, consistent with observations in human newborns. To conclude, our lamb model successfully provides a reliable representation of CDH and can be used to study its pathophysiology and potential interventions.

Early nitric oxide is not associated with improved outcomes in congenital diaphragmatic hernia

BACKGROUND

Inhaled nitric oxide (iNO) is widely used for the management of infants with congenital diaphragmatic hernia (CDH); however, evidence of benefit is limited.

METHODS

This is a multicenter cohort study using data from the Congenital Diaphragmatic Hernia Study Group between 2015 and 2020. The impact of early iNO use in the first 3 days of life prior to ECLS use on mortality or ECLS use was explored using multivariate logistic regression models and subgroup analyses.

RESULTS

Of the 1777 infants, 863 (48.6%) infants received early iNO treatment. Infants receiving iNO had lower birth weight, larger defect size, more severe pulmonary hypertension, and abnormal ventricular size and function. After controlling for these factors, early iNO use was associated with increased mortality (aOR 2.06, 95% CI 1.05-4.03, P = 0.03) and increased ECLS use (aOR 3.44, 95% CI 2.11-5.60, P < 0.001). Subgroup analyses after stratification by echocardiographic characteristics and defect size revealed no subgroup with a reduction in mortality or ECLS use.

CONCLUSIONS

Use of iNO in the first 3 days of life prior to ECLS was not associated with a reduction in mortality or ECLS use in either the regression models or the subgroup analyses. The widespread use of iNO in this vulnerable population requires reconsideration.

IMPACT

Evidence to support widespread use of iNO for infants with congenital diaphragmatic hernia is limited. The use of iNO in the first 3 days of life was associated with significantly increased mortality and ECLS use. Stratification by echocardiographic characteristics and defect size did not reveal a subgroup that benefited from iNO. Even the subset of patients with R-to-L shunts at both ductal and atrial levels, a surrogate for elevated pulmonary arterial pressures in the absence of significantly decreased LV compliance, did not benefit from early iNO use. Early iNO therapy was of no benefit in the management of acute pulmonary hypertension in infants with congenital diaphragmatic hernia, supporting reconsideration of its use in this population.

Neurodevelopmental outcome of patients with congenital gastrointestinal malformations: a systematic review and meta-analysis

AIM

Children with congenital gastrointestinal malformations may be at risk of neurodevelopmental impairment due to challenges to the developing brain, including perioperative haemodynamic changes, exposure to anaesthetics and postoperative inflammatory influences. This study aggregates existing evidence on neurodevelopmental outcome in these patients using meta-analysis.

METHOD

PubMed, Embase and Web of Science were searched for peer-reviewed articles published until October 2019. Out of the 5316 unique articles that were identified, 47 studies met the inclusion criteria and were included. Standardised mean differences (Cohen's d) between cognitive, motor and language outcome of patients with congenital gastrointestinal malformations and normative data (39 studies) or the studies' control group (8 studies) were aggregated across studies using random-effects meta-analysis. The value of (clinical) moderators was studied using meta-regression and diagnostic subgroups were compared.

RESULTS

The 47 included studies encompassed 62 cohorts, representing 2312 patients. Children with congenital gastrointestinal malformations had small-sized cognitive impairment (d=-0.435, p<0.001; 95% CI -0.567 to -0.302), medium-sized motor impairment (d=-0.610, p<0.001; 95% CI -0.769 to -0.451) and medium-sized language impairment (d=-0.670, p<0.001; 95% CI -0.914 to -0.425). Patients with short bowel syndrome had worse motor outcome. Neurodevelopmental outcome was related to the number of surgeries and length of total hospital stay, while no relations were observed with gestational age, birth weight, age and sex.

INTERPRETATION

This study shows that children with congenital gastrointestinal malformations exhibit impairments in neurodevelopmental outcome, highlighting the need for routine screening of neurodevelopment during follow-up.

Neurally adjusted ventilatory assist in neonates with congenital diaphragmatic hernia

OBJECTIVE

To measure short-term outcomes of neonates with congenital diaphragmatic hernia (CDH) while on Neurally Adjusted Ventilator Assist (NAVA), and to measure the impact of a congenitally abnormal diaphragm on NAVA ventilator indices.

STUDY DESIGN

First, we conducted a retrospective-cohort analysis of 16 neonates with CDH placed on NAVA over a treatment period of 72 h. Second, we performed a case-control study comparing NAVA level and Edi between neonates with CDH and those without CDH.

RESULTS

Compared to pre-NAVA, there were clinically meaningful improvements in PIP (p < 0.003), Respiratory Severity Score (p < 0.001), MAP (p < 0.001), morphine (p = 0.004), and midazolam use (p = 0.037). Compared to a 1:2 matched group without CDH, there was no meaningful difference in NAVA level (p = 0.286), Edi-Peak (p = 0.315), or Edi-Min (p = 0.266).

CONCLUSIONS

The potential benefits of NAVA extend to neonates with CDH. There is minimal compensatory change in Edis, and higher/lower ventilator settings compared to neonates without CDH.

Update on Congenital Diaphragmatic Hernia

Congenital diaphragmatic hernia (CDH) is a rare developmental defect of the diaphragm, characterized by herniation of abdominal contents into the chest that results in varying degrees of pulmonary hypoplasia and pulmonary hypertension (PH). Significant advances in the prenatal diagnosis and identification of prognostic factors have resulted in the continued refinement of the approach to fetal therapies for CDH. Postnatally, protocolized approaches to lung-protective ventilation, nutrition, prevention of infection, and early aggressive management of PH have led to improved outcomes in infants with CDH. Advances in our understanding of the associated left ventricular (LV) hypoplasia and myocardial dysfunction in infants with severe CDH have allowed for the optimization of hemodynamics and management of PH. This article provides a comprehensive review of CDH for the anesthesiologist, focusing on the complex pathophysiology, advances in prenatal diagnosis, fetal interventions, and optimal postnatal management of CDH.

Comparison of the 3-D patterns of the parasympathetic nervous system in the lung at late developmental stages between mouse and chicken

Although the basic schema of the body plan is similar among different species of amniotes (mammals, birds, and reptiles), the lung is an exception. Here, anatomy and physiology are considerably different, particularly between mammals and birds. In mammals, inhaled and exhaled airs mix in the airways, whereas in birds the inspired air flows unidirectionally without mixing with the expired air. This bird-specific respiration system is enabled by the complex tubular structures called parabronchi where gas exchange takes place, and also by the bellow-like air sacs appended to the main part of the lung. That the lung is predominantly governed by the parasympathetic nervous system has been shown mostly by physiological studies in mammals. However, how the parasympathetic nervous system in the lung is established during late development has largely been unexplored both in mammals and birds. In this study, by combining immunocytochemistry, the tissue-clearing CUBIC method, and ink-injection to airways, we have visualized the 3-D distribution patterns of parasympathetic nerves and ganglia in the lung at late developmental stages of mice and chickens. These patterns were further compared between these species, and three prominent similarities emerged: (1) parasympathetic postganglionic fibers and ganglia are widely distributed in the lung covering the proximal and distal portions, (2) the gas exchange units, alveoli in mice and parabronchi in chickens, are devoid of parasympathetic nerves, (3) parasympathetic nerves are in close association with smooth muscle cells, particularly at the base of the gas exchange units. These observations suggest that despite gross differences in anatomy, the basic mechanisms underlying parasympathetic control of smooth muscles and gas exchange might be conserved between mammals and birds.

Muscarinic Receptor Activation Affects Pulmonary Artery Contractility in Sheep: The Impact of Maturation and Chronic Hypoxia on Endothelium-Dependent and Endothelium-Independent Function

Giang, Michael, Demosthenes G. Papamatheakis, Dan Nguyen, Ricardo Paez, Carla Blum Johnston, Joon Kim, Alexander Brunnell, Quintin Blood, Ravi Goyal, Lawrence D. Longo, and Sean M. Wilson. Muscarinic receptor activation affects pulmonary artery contractility in sheep: the impact of maturation and chronic hypoxia on endothelium-dependent and endothelium-independent function. High Alt Med Biol. 17:122-132, 2015.-Muscarinic receptor activation in the pulmonary vasculature can cause endothelium-dependent vasodilation and smooth muscle-dependent vasoconstriction. Chronic hypoxia (CH) can modify both of these responses. This study aimed to assess the combined influence of CH and maturation on endothelium-dependent and endothelium-independent muscarinic-induced vasoreactivity. This was accomplished by performing wire myography on endothelium-intact or endothelium-disrupted pulmonary arterial rings isolated from normoxic or CH fetal and adult sheep. In endothelium-intact arteries, vasodilation was evaluated using cumulative bradykinin doses in phenylephrine and carbachol precontracted pulmonary arterial segments; and vasoconstriction was examined using cumulative doses of carbachol following bradykinin predilation. Effects of nonselective (atropine) and selective M1 (pirenzepine), M2 (AFDX116), and M3 (4-DAMP and Dau5884) muscarinic receptor antagonists were assessed in disrupted arteries. In normoxic arteries, bradykinin relaxation was twofold greater in the adult compared to fetus, while carbachol contraction was fourfold greater. In adult arteries, CH increased bradykinin relaxation and carbachol contraction. In vessels with intact endothelium, maturation and CH augmented maximal response and efficacy for carbachol constriction and bradykinin relaxation. Approximately 50%-80% of adult normoxic and CH endothelium-disrupted arteries contracted to acetylcholine, while ∼50% of fetal normoxic and ∼10% of CH arteries responded. Atropine reduced carbachol-induced contraction in all vessels. Adult normoxic vessels were most responsive to M3 antagonism, fetal to M2 antagonism, while M1 inhibition had no effect. Overall, muscarinic-induced pulmonary arterial contraction is partially endothelium dependent and appears to develop after birth. Fetuses are more reliant on M3 receptors while M2 receptors predominate in adults, whereas CH augments muscarinic-dependent pulmonary vasoconstriction in both.

Congenital Diaphragmatic hernia - a review

Congenital Diaphragmatic hernia (CDH) is a condition characterized by a defect in the diaphragm leading to protrusion of abdominal contents into the thoracic cavity interfering with normal development of the lungs. The defect may range from a small aperture in the posterior muscle rim to complete absence of diaphragm.

The pathophysiology of CDH is a combination of lung hypoplasia and immaturity associated with persistent pulmonary hypertension of newborn (PPHN) and cardiac dysfunction. Prenatal assessment of lung to head ratio (LHR) and position of the liver by ultrasound are used to diagnose and predict outcomes. Delivery of infants with CDH is recommended close to term gestation. Immediate management at birth includes bowel decompression, avoidance of mask ventilation and endotracheal tube placement if required. The main focus of management includes gentle ventilation, hemodynamic monitoring and treatment of pulmonary hypertension followed by surgery. Although inhaled nitric oxide is not approved by FDA for the treatment of PPHN induced by CDH, it is commonly used.

Extracorporeal membrane oxygenation (ECMO) is typically considered after failure of conventional medical management for infants ≥ 34 weeks’ gestation or with weight >2 kg with CDH and no associated major lethal anomalies. Multiple factors such as prematurity, associated abnormalities, severity of PPHN, type of repair and need for ECMO can affect the survival of an infant with CDH. With advances in the management of CDH, the overall survival has improved and has been reported to be 70-90% in non-ECMO infants and up to 50% in infants who undergo ECMO.

Defective parasympathetic innervation is associated with airway branching abnormalities in experimental CDH

Developmental mechanisms leading to lung hypoplasia in congenital diaphragmatic hernia (CDH) remain poorly defined. Pulmonary innervation is defective in the human disease and in the rodent models of CDH. We hypothesize that defective parasympathetic innervation may contribute to airway branching abnormalities and, therefore, lung hypoplasia, during lung development in CDH. The murine nitrofen model of CDH was utilized to study the effect of the cholinergic agonist carbachol on embryonic day 11.5 (E11.5) lung explant cultures. Airway branching and contractions were quantified. In a subset of experiments, verapamil was added to inhibit airway contractions. Sox9 immunostaining and 5-bromo-2-deoxyuridine incorporation were used to identify and quantify the number and proliferation of distal airway epithelial progenitor cells. Intra-amniotic injections were used to determine the in vivo effect of carbachol. Airway branching and airway contractions were significantly decreased in nitrofen-treated lungs compared with controls. Carbachol resulted in increased airway contractions and branching in nitrofen-treated lungs. Nitrofen-treated lungs exhibited an increased number of proliferating Sox9-positive distal epithelial progenitor cells, which were decreased and normalized by treatment with carbachol. Verapamil inhibited the carbachol-induced airway contractions in nitrofen-treated lungs but had no effect on the carbachol-induced increase in airway branching, suggesting a direct carbachol effect independent of airway contractions. In vivo treatment of nitrofen-treated embryos via amniotic injection of carbachol at E10.5 resulted in modest increases in lung size and branching at E17.5. These results suggest that defective parasympathetic innervation may contribute to airway branching abnormalities in CDH.

Understanding and treating pulmonary hypertension in congenital diaphragmatic hernia

Lung hypoplasia and pulmonary hypertension are classical features of congenital diaphragmatic hernia (CDH) and represent the main determinants of survival. The mechanisms leading to pulmonary hypertension in this malformation are still poorly understood, but may combine altered vasoreactivity, pulmonary artery remodeling, and a hypoplastic pulmonary vascular bed. Efforts have been directed at correcting the "reversible" component of pulmonary hypertension of CDH. However, pulmonary hypertension in CDH is often refractory to pulmonary vasodilators. A new emerging pattern of late (months after birth) and chronic (months to years after birth) pulmonary hypertension are described in CDH survivors. The true incidence and implications for outcome and management need to be confirmed by follow-up studies from referral centers with high patient output. In order to develop more efficient strategies to treat pulmonary hypertension and improve survival in most severe cases, the ultimate therapeutic goal would be to promote lung and vascular growth.

New Insights into Congenital Diaphragmatic Hernia - A Surgeon's Introduction to CDH Animal Models

In recent decades, new research into the developmental defects and pathophysiological basis of congenital diaphragmatic hernia (CDH) has revealed opportunities for the development of innovative therapies. Importantly, the use of animal models to represent this anomaly in the laboratory has resulted in the discovery of many important genetic, epigenetic, and other molecular contributors to this condition. In this review, the most commonly used and newly devised animal models of CDH are presented to familiarize the reader with the latest innovations in the basic sciences.

Recent advances in late lung development and the pathogenesis of bronchopulmonary dysplasia

In contrast to early lung development, a process exemplified by the branching of the developing airways, the later development of the immature lung remains very poorly understood. A key event in late lung development is secondary septation, in which secondary septa arise from primary septa, creating a greater number of alveoli of a smaller size, which dramatically expands the surface area over which gas exchange can take place. Secondary septation, together with architectural changes to the vascular structure of the lung that minimize the distance between the inspired air and the blood, are the objectives of late lung development. The process of late lung development is disturbed in bronchopulmonary dysplasia (BPD), a disease of prematurely born infants in which the structural development of the alveoli is blunted as a consequence of inflammation, volutrauma, and oxygen toxicity. This review aims to highlight notable recent developments in our understanding of late lung development and the pathogenesis of BPD.