Pulmonary Hypertension

Targeted Neonatal Echocardiography in the Management of Neonatal Pulmonary Hypertension

Pulmonary hypertension (PH) in neonates, originating from a range of disease states with heterogeneous underlying pathophysiology, is associated with significant morbidity and mortality. Although the final common pathway is a state of high right ventricular afterload leading to compromised cardiac output, multiple hemodynamic phenotypes exist in acute and chronic PH, for which cardiorespiratory treatment strategies differ. Comprehensive appraisal of pulmonary pressure, pulmonary vascular resistance, cardiac function, pulmonary and systemic blood flow, and extrapulmonary shunts facilitates delivery of individualized cardiovascular therapies in affected newborns.

How to diagnose and treat acute pulmonary hypertension when you have no cardiology support

Acute pulmonary hypertension (aPH) is a complex, physiology-driven disorder that causes critical illness in newborns, the hallmark of which is elevated pressure in the pulmonary vascular bed. Several underlying hemodynamic phenotypes exist, including classic arterial aPH with resistance-driven elevations in pulmonary arterial pressure (PAP), alongside flow-driven aPH from left-to-right shunt lesions, and primary left ventricular dysfunction with pulmonary venous hypertension and elevated left atrial pressure. Targeted neonatal echocardiography (TnECHO) is an important tool for evaluation of hemodynamics in aPH and is highly useful for evaluating modulators of disease and targeting cardiovascular therapy. The diagnostic approach to aPH includes confirmation of elevation of PAP, evaluation of the cause and exclusion of structural cardiac disease, assessment of the response of the myocardium to adverse loading conditions, and appraisal of the adequacy of systemic blood flow. Therapeutic goals include support of right ventricular (RV) function, RV afterload reduction, and selection of cardiotropic agents that support underlying pathophysiology without adverse effects on heart rate or pulmonary vascular resistance in addition to routine supportive intensive care. Training programs for TnECHO exist across multiple jurisdictions and strong correlation with pediatric cardiology assessment has been demonstrated. Future directions include adapting TnECHO training with a greater focus on achieving competency, and further research into the role of the modality in providing individualized cardiovascular care for patients with heterogenous underlying physiology, and its effect on key neonatal outcomes.

Dead space ratio as a tool in nitric oxide weaning: a study in pulmonary hypertensive disease

OBJECTIVES

To describe the association between successful weaning of inhaled nitric oxide and trends in dead space ratio during such weans in patients empirically initiated on nitric oxide therapy out of concern of pulmonary hypertensive crisis.

PATIENTS

Children in a cardiac intensive care unit initiated on inhaled nitric oxide out of clinical concern for pulmonary hypertensive crisis retrospectively over 2 years.

MEASUREMENTS AND MAIN RESULTS

Twenty-seven patients were included, and nitric oxide was successfully discontinued in 23/27. These patients exhibited decreases in dead space ratio (0.18 versus 0.11, p = 0.047) during nitric oxide weaning, and with no changes in dead space ratio between pre- and post-nitric oxide initiation (p = 0.88) and discontinuation (p = 0.63) phases. These successful patients had a median age of 10 months [4.0, 57.0] and had a pre-existent diagnosis of CHD in 6/23 and pulmonary hypertension in 2/23. Those who failed nitric oxide discontinuation trended with a higher dead space ratio at presentation (0.24 versus 0.10), were more likely to carry a prior diagnosis of pulmonary hypertension (50% versus 8.7%), and had longer mechanical ventilation days (5 versus 12).

CONCLUSIONS

Patients empirically placed on nitric oxide out of concern of pulmonary hypertensive crisis and successfully weaned off showed unchanged or decreased dead space ratio throughout the initiation to discontinuation phases of nitric oxide therapy. Trends in dead space ratio may aid in determining true need for nitric oxide and facilitate effective weaning. Further studies are needed to directly compare trends between success and failure groups.

Bioinformatic analysis of dysregulated circular RNAs in pediatric pulmonary hypertension linked congenital heart disease

BACKGROUND

Circular RNAs (circRNAs) may play important roles in the progression of pulmonary arterial hypertension. However, the potential roles they play in childhood pulmonary arterial hypertension associated congenital heart disease (CHD) progression remains unclear.

METHODS

Thirteen human plasma samples including eight from pulmonary arterial hypertension secondary to CHD patients and five from a control group were analyzed using the Arraystar Human circRNA array. The relative expression levels of five differentially expressed circRNAs in pulmonary arterial hypertension were detected using real-time polymerase chain reaction (PCR) analysis. In parallel, these levels were also taken on control samples from 32 CHD patients. We used miRanda and TargetScan software packages to predict potential microRNA (miRNA)targets, which were then combined into a circRNA-miRNA-messenger RNA (mRNA) network.

RESULTS

Twenty-seven circRNAs (three upregulated and 24 downregulated) were differentially expressed between the pulmonary arterial hypertension and control groups. Compared to control group levels, circ_003416 expression in the pulmonary arterial hypertension group was significantly downregulated, while circ_005372 expression, in contrast, was significantly upregulated. The differential expression of these circRNAs was mainly linked to variation in levels of oxidative phosphorylation and tight junction signaling.

CONCLUSIONS

We identified one overexpressed and one underexpressed circRNA in plasma samples from children with CHD associated pulmonary arterial hypertension. Bioinformatic analysis indicated these dysregulated circRNAs might be associated with the occurrence and regulation of pulmonary arterial hypertension.

Characterization of Inhaled Nitric Oxide Use for Cardiac Indications in Pediatric Patients

OBJECTIVES

Characterize the use of inhaled nitric oxide (iNO) for pediatric cardiac patients and assess the relationship between patient characteristics before iNO initiation and outcomes following cardiac surgery.

DESIGN

Observational cohort study.

SETTING

PICU and cardiac ICUs in seven Collaborative Pediatric Critical Care Research Network hospitals.

PATIENTS

Consecutive patients, less than 18 years old, mechanically ventilated before or within 24 hours of iNO initiation. iNO was started for a cardiac indication and excluded newborns with congenital diaphragmatic hernia, meconium aspiration syndrome, and persistent pulmonary hypertension, or when iNO started at an outside institution.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Four-hundred seven patients with iNO initiation based on cardiac dysfunction. Cardiac dysfunction patients were administered iNO for a median of 4 days (2-7 d). There was significant morbidity with 51 of 407 (13%) requiring extracorporeal membrane oxygenation and 27 of 407 (7%) requiring renal replacement therapy after iNO initiation, and a 28-day mortality of 46 of 407 (11%). Of the 366 (90%) survivors, 64 of 366 patients (17%) had new morbidity as assessed by Functional Status Scale. Among the postoperative cardiac surgical group (n = 301), 37 of 301 (12%) had a superior cavopulmonary connection and nine of 301 (3%) had a Fontan procedure. Based on echocardiographic variables prior to iNO (n = 160) in the postoperative surgical group, right ventricle dysfunction was associated with 28-day and hospital mortalities (both, p < 0.001) and ventilator-free days (p = 0.003); tricuspid valve regurgitation was only associated with ventilator-free days (p < 0.001), whereas pulmonary hypertension was not associated with mortality or ventilator-free days.

CONCLUSIONS

Pediatric patients in whom iNO was initiated for a cardiac indication had a high mortality rate and significant morbidity. Right ventricular dysfunction, but not the presence of pulmonary hypertension on echocardiogram, was associated with ventilator-free days and mortality.

Mortality from Pulmonary Hypertension in the Pediatric Cardiac ICU

Rationale: Patients with pulmonary hypertension (PH) admitted to pediatric cardiac ICUs are at high risk of mortality. Objectives: To identify factors associated with mortality in cardiac critical care admissions with PH. Methods: We evaluated medical admissions with PH to Pediatric Cardiac Critical Care Consortium institutions over 5 years. PH was standardly defined in the clinical registry by diagnosis and/or receipt of intensive care-level pulmonary vasodilator therapy. Multivariable logistic regression identified independent associations with mortality. Measurements and Main Results: We analyzed 2,602 admissions; mortality was 10% versus 3.9% for all other medical admissions. Covariates most strongly associated with mortality included invasive ventilation (adjusted odds ratio, 44.8; 95% confidence interval, 6.2-323), noninvasive ventilation (19.7; 2.8-140), cardiopulmonary resuscitation (8.9; 5.6-14.1), and vasoactive infusions (4.8; 2.6-8.8). Patients receiving both invasive ventilation and vasoactive infusions on admission Days 1 and 2 had an observed mortality rate of 29.2% and 28.6%, respectively, compared with <5% for those not receiving either. Vasoactive infusions emerged as the dominant early risk factor for mortality, increasing the absolute risk of mortality on average by 6.4% when present on admission Day 2. Conclusions: Patients with PH admitted to pediatric cardiac critical care units have high mortality rates. Those receiving invasive ventilation and vasoactive infusions on Day 1 or Day 2 had an observed mortality rate that was more than fivefold greater than that of those who did not. These data highlight the illness severity of patients with PH in this setting and could help inform conversations with families regarding the prognosis.

Comparison of l-Carnitine and l-Carnitine HCL salt for targeted lung treatment of pulmonary hypertension (PH) as inhalation aerosols: Design, comprehensive characterization, in vitro 2D/3D cell cultures, and in vivo MCT-Rat model of PH

Disrupted l-Carnitine (L-Car) homeostasis has been implicated in the development of pulmonary hypertension (PH). L-Car has been administered orally and intravenously causing systemic side effects. To the authors' knowledge, there are no reports using L-Car or L-Car HCl as an inhaled aerosol through the respiratory route in a targeted manner either from dry powder inhaler (DPI) or liquid delivery system. The purpose of the comprehensive and systematic comparative study between L-Car and L-Car HCl salt was to design and develop dry powder inhalers (DPIs) of each. This was followed by comprehensive physicochemical characterization, in vitro cell viability as a function of dose on 2D human pulmonary cell lines from different lung regions and in vitro cell viability on 3D small airway epithelia human primary cells at the air-liquid interface (ALI). In addition in vitro transepithelial electrical resistance (TEER) in air-interface culture (AIC) conditions on 2D human pulmonary cell line and 3D small airway epithelia human primary cells was carried out. In vitro aerosol dispersion performance using three FDA-approved human DPI devices with different device properties was also examined. Following advanced spray drying under various conditions, two spray drying pump rates (low and medium) were found to successfully produce spray-dried L-Car powders while four spray drying pump rates (low, medium, medium-high, and high) all resulted in the production of spray-dried L-Car HCl powders. Raw L-Car and L-Car HCl were found to be crystalline. All SD powders retained crystallinity following spray drying and polymorphic interconversion in the solid-state was identified as the mechanism for retaining crystallinity after the advanced spray drying process. All SD powders aerosolized readily with all three human DPI devices. However, the in vitro dispersion parameters for the SD powders was not conducive for in vivo administration to rats in DPIs due to hygroscopicity and nanoaggreation. In vivo rat studies were successfully accomplished using inhaled liquid aerosols. Safety was successfully demonstrated in vivo in healthy Sprague Dawley rats. Furthermore, therapeutic efficacy was successfully demonstrated in vivo in the monocrotaline (MCT)-rat model of PH after two weeks of daily L-Car inhalation aerosol treatment.

Advanced therapeutic inhalation aerosols of a Nrf2 activator and RhoA/Rho kinase (ROCK) inhibitor for targeted pulmonary drug delivery in pulmonary hypertension: design, characterization, aerosolization, in vitro 2D/3D human lung cell cultures, and in vivo efficacy

Inhalable nanostructured microparticles of simvastatin, a Nrf2 activator and RhoA/Rho kinase (ROCK) inhibitor, were rationally designed for targeted pulmonary delivery as dry powder inhalers (DPIs) for the treatment of pulmonary hypertension (PH). Advanced particle engineering design technology was employed to develop inhalable dry powders using different dilute feed concentrations and spray drying pump rates. Several analytical techniques were used comprehensively to characterize the physicochemical properties of the resulting powders. Scanning electron microscopy (SEM) was used to visualize particle morphology (shape), surface structure, size, and size distribution. Karl Fischer titration (KFT) was employed to quantify the residual water content in the powders. X-ray powder diffraction (XRPD) was used to determine crystallinity. Hot-stage microscopy (HSM) under cross-polarizing lens was used to observe the presence or absence of birefringence characteristic of crystallinity. Differential scanning calorimetry (DSC) was employed to quantify thermotropic phase behavior. Attenuated total reflectance (ATR)-Fourier-transform infrared (FTIR) spectroscopy and Raman spectroscopy were used to determine the molecular fingerprint of simvastatin powders before and after particle engineering design. In vitro aerosol dispersion performance was performed with three different Food and Drug Administration (FDA)-approved human DPI devices. Cell viability and transepithelial electrical resistance (TEER) were demonstrated using different in vitro human pulmonary cell two and three-dimensional models at the air-liquid interface, and in vivo safety in healthy rats by inhalation. Efficacy was demonstrated in the in vivo lamb model of PH. Four different inhalable powders of simvastatin were successfully produced. They possessed nanostructured surfaces and were in the inhalable size range. Simvastatin retained its crystallinity following particle engineering design. The more dilute feed concentration spray dried at the lower pump rate produced the smallest particles. All powders successfully aerosolized with all three DPI human devices. Inhaled simvastatin as an aerosol restored the endothelial function in the shunt lamb model of PH, as demonstrated by the reduction of pulmonary vascular resistance (PVR) in response to the endothelium-dependent vasodilator acetylcholine.The reviews of this paper are available via the supplemental material section.

Inhalable Nanoparticles/Microparticles of an AMPK and Nrf2 Activator for Targeted Pulmonary Drug Delivery as Dry Powder Inhalers

Metformin is an activator of the AMPK and Nrf2 pathways which are important in the pathology of several complex pulmonary diseases with unmet medical needs. Organic solution advanced spray drying in the absence of water in closed-mode was used to design and develop respirable dry powders. Following comprehensive characterization, the influence of physicochemical properties was correlated with performance as aerosols using inertial impaction and three different human dry powder inhaler (DPI) devices varying in device properties. In vitro cell assays were conducted to test safety in 2D human pulmonary cell lines and in 3D small airway epithelia comprising primary cells at the air-liquid interface (ALI). In addition, in vitro transepithelial electrical resistance (TEER) was carried out. Metformin remained crystalline following advanced spray drying under these conditions. All SD powders consisted of nanoparticles/microparticles in the solid state. In vitro aerosol dispersion performance showed high aerosolization for all SD metformin powders with all DPI devices tested. High emitted dose for all powders with all three DPI devices was measured. Differences in other aerosol performance parameters and the interplay between the properties of different formulations produced at specific pump rates and the three different DPI devices were correlated with spray drying pump rate and device properties. Safety over a wide metformin dose range was also demonstrated in vitro. Aerosol delivery of metformin nanoparticles/microparticles has the potential to be a new "first-in-class" therapeutic for the treatment of a number of pulmonary diseases including pulmonary vascular diseases such as pulmonary hypertension.

Sugammadex Neuromuscular Blockade Reversal Associated With Lower Postoperative Arterial Carbon Dioxide Levels After Congenital Cardiac Surgery

OBJECTIVE

To compare postoperative arterial blood gas samples and requirement for respiratory support between patients who received sugammadex versus neostigmine reversal before extubation after congenital cardiac surgery.

DESIGN

Retrospective, cross-sectional study.

SETTING

Single-center, university-based, tertiary care hospital.

PARTICIPANTS

Patients with congenital heart disease undergoing surgery with cardiopulmonary bypass.

INTERVENTIONS

Chart review.

MEASUREMENTS AND MAIN RESULTS

The first postoperative arterial blood gas measurements were abstracted from electronic medical records, and reintubation or use of positive- pressure respiratory support within the first 24 postoperative hours was documented. Of the 237 charts reviewed, 111 (47%) patients received sugammadex reversal and 126 (53%) received neostigmine. Multivariate models showed that patients with 2-ventricle congenital heart disease who received sugammadex had lower postoperative arterial carbon dioxide partial pressure (PaCO₂) values (coefficient -3.1, 95% confidence interval [CI] -5.9 to -0.4; p = 0.026) and required less- noninvasive positive- pressure ventilation (odds ratio 0.3, 95% CI 0.1-0.8; p = 0.021). Single-ventricle congenital heart disease patients who received sugammadex had higher postoperative pH values (coefficient 0.04, 95% CI 0.01-0.06; p = 0.01) and lower PaCO₂ values (coefficient -5.2, 95% CI -9.6 to -0.8; p = 0.021).

CONCLUSION

Sugammadex reversal was associated with lower postoperative PaCO₂ values. In addition, sugammadex reversal was associated with less need for noninvasive positive- pressure ventilation in 2-ventricle patients. The magnitude of the effect appears modest, therefore the clinical significance remains unclear. Additional studies focused on investigating particular patient populations, such as infants, single-ventricle congenital heart disease, or patients with pulmonary hypertension, are needed to identify whether these patients appreciate a greater benefit from sugammadex reversal.

Extracorporeal Membrane Oxygenation in Pediatric Pulmonary Hypertension

OBJECTIVE

To describe the epidemiology, critical care interventions, and mortality of children with pulmonary hypertension receiving extracorporeal membrane oxygenation.

DESIGN

Retrospective analysis of prospectively collected multicenter data.

SETTING

Data entered into the Extracorporeal Life Support Organization database between January 2007 and November 2018.

PATIENTS

Pediatric patients between 28 days and 18 years old with a diagnosis of pulmonary hypertension.

MEASUREMENTS AND MAIN RESULTS

Six hundred thirty-four extracorporeal membrane oxygenation runs were identified (605 patients). Extracorporeal membrane oxygenation support type was pulmonary (43.1%), cardiac (40.2%), and extracorporeal cardiopulmonary resuscitation (16.7%). The majority of cannulations were venoarterial (80.4%), and 30% had a pre-extracorporeal membrane oxygenation cardiac arrest. Mortality in patients with pulmonary hypertension was 51.3% compared with 44.8% (p = 0.001) in those without pulmonary hypertension. In univariate analyses, significant predictors of mortality included age less than 6 months and greater than 5 years; pre-extracorporeal membrane oxygenation cardiac arrest; pre-extracorporeal membrane oxygenation blood gas with pH less than 7.12, PaCO2 greater than 75, PaO2 less than 35, and arterial oxygen saturation less than 60%; extracorporeal membrane oxygenation duration greater than 280 hours; extracorporeal cardiopulmonary resuscitation; and extracorporeal membrane oxygenation complications including cardiopulmonary resuscitation, inotropic support, myocardial stun, tamponade, pulmonary hemorrhage, intracranial hemorrhage, seizures, other hemorrhage, disseminated intravascular coagulation, renal replacement therapy, mechanical/circuit problem, and metabolic acidosis. A co-diagnosis of pneumonia was associated with significantly lower odds of mortality (odds ratio, 0.5; 95% CI, 0.3-0.8). Prediction models were developed using three sets of variables: 1) pre-extracorporeal membrane oxygenation (age, absence of pneumonia, and pH < 7.12; area under the curve, 0.62); 2) extracorporeal membrane oxygenation related (extracorporeal cardiopulmonary resuscitation, any neurologic complication, pulmonary hemorrhage, renal replacement therapy, and metabolic acidosis; area under the curve, 0.72); and 3) all variables combined (area under the curve, 0.75) (p < 0.001).

CONCLUSIONS

Children with pulmonary hypertension who require extracorporeal membrane oxygenation support have a significantly greater odds of mortality compared with those without pulmonary hypertension. Risk factors for mortality include age, absence of pneumonia, pre-extracorporeal membrane oxygenation acidosis, extracorporeal cardiopulmonary resuscitation, pulmonary hemorrhage, neurologic complications, renal replacement therapy, and acidosis while on extracorporeal membrane oxygenation. Identification of those pulmonary hypertension patients requiring extracorporeal membrane oxygenation who are at even higher risk for mortality may inform clinical decision-making and improve prognostic awareness.

Moving Beyond the Stethoscope: Diagnostic Point-of-Care Ultrasound in Pediatric Practice

Diagnostic point-of-care ultrasound (POCUS) is a growing field across all disciplines of pediatric practice. Machine accessibility and portability will only continue to grow, thus increasing exposure to this technology for both providers and patients. Individuals seeking training in POCUS should first identify their scope of practice to determine appropriate applications within their clinical setting, a few of which are discussed within this article. Efforts to build standardized POCUS infrastructure within specialties and institutions are ongoing with the goal of improving patient care and outcomes.

Pediatric Perioperative Pulmonary Arterial Hypertension: A Case-Based Primer

The perioperative period is an extremely tenuous time for the pediatric patient with pulmonary arterial hypertension. This article will discuss a multidisciplinary approach to preoperative planning, the importance of early identification of pulmonary hypertensive crises, and practical strategies for postoperative management for this unique group of children.