Clinical applications of inhaled nitric oxide in children with pulmonary hypertension

Cardiopulmonary Resuscitation in Infants and Children With Cardiac Disease: A Scientific Statement From the American Heart Association

Cardiac arrest occurs at a higher rate in children with heart disease than in healthy children. Pediatric basic life support and advanced life support guidelines focus on delivering high-quality resuscitation in children with normal hearts. The complexity and variability in pediatric heart disease pose unique challenges during resuscitation. A writing group appointed by the American Heart Association reviewed the literature addressing resuscitation in children with heart disease. MEDLINE and Google Scholar databases were searched from 1966 to 2015, cross-referencing pediatric heart disease with pertinent resuscitation search terms. The American College of Cardiology/American Heart Association classification of recommendations and levels of evidence for practice guidelines were used. The recommendations in this statement concur with the critical components of the 2015 American Heart Association pediatric basic life support and pediatric advanced life support guidelines and are meant to serve as a resuscitation supplement. This statement is meant for caregivers of children with heart disease in the prehospital and in-hospital settings. Understanding the anatomy and physiology of the high-risk pediatric cardiac population will promote early recognition and treatment of decompensation to prevent cardiac arrest, increase survival from cardiac arrest by providing high-quality resuscitations, and improve outcomes with postresuscitation care.

Current Practices and Attitudes Regarding Use of Inhaled Nitric Oxide in the NICU: Results From a Survey of Members of the National Association of Neonatal Nurse Practitioners

Background:

Excessive supplemental oxygen exposure in the neonatal intensive care unit (NICU) can be associated with oxygen-related toxicities, which can lead to negative clinical consequences. Use of inhaled nitric oxide (iNO) can be a successful strategy for avoiding hyperoxia in the NICU. iNO selectively produces pulmonary vasodilation and has been shown to improve oxygenation parameters across the spectrum of disease severity, from mild to very severe, in neonates with hypoxic respiratory failure associated with persistent pulmonary hypertension of the newborn.

Purpose:

An online survey was conducted among members of the National Association of Neonatal Nurse Practitioners to gain insight into the level of understanding and knowledge among neonatal nurse practitioners (NNPs) about optimizing supplemental oxygen exposure and the use of iNO in the NICU setting.

Results:

Of 937 NNP respondents, 51% reported that their healthcare team typically waits until the fraction of inspired oxygen level is 0.9 or more before adding iNO in patients not responding to oxygen ventilation alone. Among respondents with 1 or more iNO-treated patients per month, only 35% reported they know the oxygenation index level at which iNO should be initiated. Less than 20% of NNPs reported perceived benefits associated with early initiation of iNO for preventing progression to use of extracorporeal membrane oxygenation or reducing the length of hospital stay, and about one-third of respondents reported they believe early iNO use minimizes hyperoxia.

Implications for Practice:

More education is needed for NNPs regarding the negative effects of oxidative stress in neonates.

Implications for Research:

Additional clinical trials investigating the most beneficial strategies for avoiding neonatal hyperoxia are warranted.

Advances in therapies for pediatric pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by progressive obliteration of the pulmonary vasculature, leading to right heart failure and death if left untreated. Prior to the current treatment era, pulmonary hypertension carried a poor prognosis with a high mortality rate, but its prognosis has changed over the past decades in relation to new therapeutic agents. Nevertheless, pulmonary hypertension continues to be a serious condition, which is extremely challenging to manage. The data in children are often limited owing to the small number of patients, and extrapolation from adults to children is not straightforward. While none of these new therapeutic agents have been specifically approved for children, there is evidence that each can appropriately benefit the PAH child. We review the current understanding of pediatric pulmonary hypertension, classification, diagnostic evaluation and available treatment. A description of targeted pharmacological therapy and new treatments in children is outlined.

Nitric oxide and pulmonary hypertension

Pulmonary hypertension is a serious complication of a number of lung and heart diseases that is characterized by peripheral vascular structural remodeling and loss of vascular tone. Nitric oxide can modulate vascular injury and interrupt elevation of pulmonary vascular resistance selectively; however, it can also produce cytotoxic oxygen radicals and exert cytotoxic and antiplatelet effects. The balance between the protective and adverse effects of nitric oxide is determined by the relative amount of nitric oxide and reactive radicals. Nitric oxide has been shown to be clinically effective in the treatment of congenital heart disease, mitrial valvular disease combined with pulmonary hypertension and in orthotropic cardiac transplantation patients. Additionally, new therapeutic modalities for the treatment of pulmonary hypertension, phosphodiesterase inhibitors, natriuretic peptides and aqueous nitric oxide are also effective for treatment of elevated pulmonary vascular resistance.

Current treatment options in children with pulmonary arterial hypertension and experiences with oral bosentan

Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by vasoconstriction and progressive remodelling of the pulmonary arterial wall leading to right ventricular failure and death. Idiopathic PAH (IPAH) and PAH associated with congenital heart defects account for the majority of paediatric patients with PAH. During the last few decades, several pharmacological approaches have been introduced, including calcium channel-blockers (CCBs), prostacyclin analogues, endothelin receptor antagonists and, most recently, phosphodiesterase inhibitors. This paper reviews the treatment options available to children with a special focus on the initial experience with bosentan. Although CCBs have been shown to increase survival in IPAH, the beneficial effect appears to be limited to a small number of patients, defined as 'responders' to the vasoreactivity testing. With the availability of prostacyclin (intravenous epoprostenol) and then prostacyclin analogues, the treatment options have increased markedly and particularly in patients who have not responded to conventional therapy. Although epoprostenol has been shown to be efficacious in PAH, the drug is not ideal owing to serious complications arising from the invasive mode of application, particularly in children. Phosphodiesterase-5 inhibitors have also shown beneficial effects. Targeting the endothelin (ET) system with the oral, dual ET(A)/ET(B) receptor antagonist, bosentan has been demonstrated to improve the cardiopulmonary haemodynamics, exercise capacity, quality-of-life and survival in adult patients with PAH. Specific ET(A) antagonists may also present the same beneficial profile. Recent experience with bosentan in paediatric patients with PAH indicates that the results obtained in adult patients may be extrapolated to children, thus offering a safe and effective therapy that is easy to administer.

Advances in the management of sickle cell disease

This article summarizes my presentation at the Pediatric Hematology-Oncology Symposium in honor of Dr. Stephen A. Feig in April 2005. Areas highlighted reflect key topics whose evolution parallel and were impacted by Steve's exceptional academic career. It is by no means an exhaustive summation of all advances in the biology and treatment of sickle cell disease. The interested reader is encouraged to consider a number of well written recently published reviews that cover additional areas of scientific and medical advancement in the pathophysiology and care of sickle cell disease 1-5.

Total anomalous pulmonary venous connection: an analysis of current management strategies in a single institution

BACKGROUND

Repair of total anomalous pulmonary venous connection (TAPVC) continues to be associated with significant mortality. We reviewed patients undergoing consecutive TAPVC repairs over a 10-year period at Children's Hospital Boston. The impact of current surgical and perioperative management strategies on short-term outcomes (postrepair pulmonary venous obstruction and mortality) is evaluated.

METHODS

All patients with surgically corrected TAPVC from November 1989 to December 2000 were included. Charts were reviewed for patient demographics, operation variables, and postoperative course.

RESULTS

There were 123 patients in the cohort, of which 72 (59%) were male. The median age and weight at operation were 10 days and 3.6 kg, respectively. Sixty-eight (55%) patients presented with pulmonary venous obstruction, and 65 (53%) underwent emergent TAPVC repair. Thirty-nine (32%) had single-ventricle anatomy, and 84 (68%) had two-ventricle anatomy. Thirty patients (24%) died. Kaplan-Meier survival at 1 month was 65% (95% confidence interval [CI], 55% to 75%) for single-ventricle patients versus 90% (95% CI, 90% to 100%) for two-ventricle patients; at 36 months it was 47% (95% CI, 35% to 59%) versus 87% (95% CI, 81% to 93%), respectively. By Cox multivariable regression analysis, a single ventricle (p < 0.001, hazard ratio, 4.8; 95% CI, 2.5 to 9.2) was an independent mortality risk factor. Prerepair pulmonary venous obstruction was a multivariate risk factor for death among single-ventricle patients. Postrepair pulmonary venous obstruction occurred in 11%. If year of operation is used as a predictor, two-ventricle patient survival has significantly improved (p < 0.05).

CONCLUSIONS

Despite current interventions, single-ventricle patients continue to have a worse prognosis than two-ventricle patients.

Improvement of bypass circuit biocompatibility: comparison and combination of heparin-coated circuit and nitric oxide gas infusion

OBJECTIVES

Nitric oxide (NO) gas infusion to the oxygenator, as well as heparin-coated bypass circuits, have been reported to attenuate blood activation induced by the interaction with the artificial surfaces of an extracorporeal bypass circuit. Using a mock circulation model, we compared the effect of each and also evaluated the effect of their combination on attenuating bypass-induced blood activation.

METHODS

A miniature closed bypass circuit was primed with diluted fresh human blood and perfused for 180 minutes using a centrifugal pump. NO gas (0, 50, or 100 ppm) was infused to the oxygenator sweep gas of either a non-heparin-coated or a heparin-coated circuit. Platelet counts, beta-thromboglobulin, platelet factor 4, complement-3 activation products and granulocyte elastase were measured at 0, 30, 60, 120, and 180 minutes after starting the perfusion.

RESULTS

One hundred ppm of NO was statistically equivalent to the heparin-coated circuit for attenuating bypass-induced blood activation, and a combination of the two significantly surpassed the results of either modification alone. Fifty ppm of NO alone provided only a slight attenuation of blood activation as compared with the non-heparin-coated circuit, though the difference was not significant. A combination of 50 ppm NO and the heparin-coated circuit did not significantly enhance the effects of the heparin-coated circuit alone.

CONCLUSIONS

The combination of NO gas infusion and heparin-coated circuits appears to be a useful and promising modification for enhancing the attenuation of bypass-induced blood activation, though the optimal dose of NO infusion in terms of effectiveness and adverse effects to the whole body remains to be established.

Pathobiology of pulmonary hypertension: Impact on clinical management

Our previous studies showed how analysis of pulmonary vascular changes on lung biopsy tissue and on angiography added to the hemodynamic assessment of pulmonary vascular resistance in predicting the success of a surgical repair. Both the potential for heightened vasoreactivity in the early postoperative period and for reversibility of pulmonary vascular disease at later follow-up were correlated with qualitative and quantitative evaluation of arterial changes. The ability of continuous intravenous prostacylin to arrest progression and even induce regression of structurally advanced pulmonary vascular disease in some cases has led to rethinking how pathological material can be useful in clinical decision making. The presence of occlusive changes and particularly plexiform lesions was thought to represent irreversible disease, but the observation that ongoing cellular proliferation and connective tissue synthesis occurs even in advanced lesions thought to represent end stage 'burnt-out' lesions, led to re-evaluation of the potential of biologically reversing the disease process. Our laboratory has used clinical material, cultured cells, and studies in experimental animals to gain new insights into some of the mechanisms which lead to the progression of vascular changes, and has used this information in strategies aimed at arresting progression and, more recently, inducing regression of pulmonary hypertension and associated vascular lesions. Specifically, we have focused on the increased activity of an endogenous vascular elastase (EVE) and expression of the glycoproteins tenascin and fibronectin in the pathobiology of pulmonary hypertension. This report will first review our studies in children with congenital heart defects, assessment of reversibility of pulmonary hypertension, and then discuss more recent work addressing cellular and molecular mechanisms aimed at developing newer therapeutic strategies. Copyright 2000 by W.B. Saunders Company

Essentials of Nitric Oxide for the Pediatric (Cardiac) Anesthesiologist

Short- and long-term survival rates for the operative treat ment of congenital heart disease (CHD) have improved significantly in the past 2 decades. The increasing sophisti cation of the pediatric cardiologist's diagnostic armamen tarium has led to more pervasive use of fetal screening with echocardiography. Early diagnosis and pre-emptive care of the neonate with complex CHD have allowed interventional strategies in the catheterization suite or the operating room to be optimized in both the timing and the quality of pallia tive or corrective procedures. Medications such as prosta glandin E and ventilator strategies using hypoxic and hyper carbic inspired gases exemplify therapies benefitting the contemporary neonate with CHD, often allowing stabiliza tion of the patient before surgery. Surgical care of neonates, infants, and children with CHD has also improved. Insights into maturational differences in myocardial and autonomic function have led to more appropriate myocardial protection strategies and pharmacologic support of the circulation. Recognition of those anomalies in which total correction in the neonate is desirable has stimulated improvements in the technical and cognitive skills of pediatric cardiovascular sur geons and pediatric cardiac anesthesiologists to meet these challenges. The goal of this article is to provide the pediatric anesthesiologist with an overview of inhaled nitric oxide and its relevance to clinical practice.

Postoperative nitric oxide therapy in children with congenital heart disease. Can the need be predicted?

The necessity for postoperative inhaled nitric oxide (NO) therapy and predictive factors for that need were retrospectively analysed in 457 paediatric patients at risk of pulmonary hypertensive events following open-heart surgery for congenital heart disease. Inhaled NO was given postoperatively to 46% of the study group and to 23% of all patients undergoing open-heart surgery during the study period. Factors associated with increased need for postoperative NO were age <1 year, Down's syndrome, preoperative pulmonary hypertension and increased pulmonary vascular resistance. Using a multivariate model based on these factors, 73% of the patients who were given NO were identified. Thus, in a setting with unrestricted access to NO therapy, almost half of the patients with cardiac lesions that commonly give rise to postoperative pulmonary hypertension were given postoperative NO. Seventy-three percent of postoperative NO treatment was associated with a relatively small number of pre- and perioperative patient-related risk factors.

Inhaled nitric oxide in primary pulmonary hypertension: a safe and effective agent for predicting response to nifedipine

OBJECTIVES

The purpose of this study was to assess the utility of inhaled nitric oxide (NO), a selective pulmonary vasodilator, for predicting the safety and acute hemodynamic response to high-dose oral nifedipine in primary pulmonary hypertension (PPH).

BACKGROUND

A significant decrease in pulmonary vascular resistance with an oral nifedipine challenge is predictive of an improved prognosis, and potential clinical efficacy in PPH. However, the required nifedipine trial carries significant first-dose risk of hypotension. While inhaled NO has been recommended for assessing pulmonary vasodilator reserve in PPH, it is not known whether it predicts the response to nifedipine.

METHODS

Seventeen patients with PPH undergoing a nifedipine trial were assessed for hemodynamic response to inhaled NO at 80 parts per million for 5 minutes. The nifedipine trial consisted of 20 mg of nifedipine hourly for 8 hours unless limited by hypotension or intolerable side effects. Patients were classified as responders and nonresponders with positive response defined as > or =20% reduction in mean pulmonary artery pressure (mPA) or pulmonary vascular resistance (PVR) with the vasodilator administration.

RESULTS

NO was safely administered to all participants. Seven of 17 (41.2%) responded to NO, and 8 of the 17 to nifedipine (47.1%). Nifedipine was safely administered in 14 of the 17. Three suffered either mild or severe hypotension, including one death. All NO responders also responded to nifedipine, and 9 of the 10 NO nonresponders were nifedipine nonresponders, representing a sensitivity of 87.5%, specificity of 100%, and overall predictive accuracy of 94%. All NO responders tolerated a full nifedipine trial without hypotension. There was a highly significant correlation between the effects of NO and nifedipine on PVR (r=0.67, p=0.003).

CONCLUSIONS

The pulmonary vascular response to inhaled NO accurately predicts the acute hemodynamic response to nifedipine in PPH, and a positive response to NO is associated with a safe nifedipine trial. In patients comparable with those evaluated, a trial of nifedipine in NO nonresponders appears unwarranted and potentially dangerous.

Management of functional pulmonary atresia with isoproterenol in a neonate with Ebstein's anomaly

Ebstein's anomaly is a rare congenital cardiac anomaly showing significant clinical manifestations with a high mortality rate in the neonatal period. The prognosis of the patient is essentially determined by the severity in morphological changes, however, high pulmonary vascular resistance in the neonatal period may aggravate tricuspid regurgitation and lead to functional pulmonary atresia. We describe a critically ill neonate with morphologically mild Ebstein's anomaly who was successfully managed with intensive care including isoproterenol administration for functional pulmonary atresia. Isoproterenol is a potent pulmonary vasodilator with inotropic and chronotropic effects, and seemed to decrease the pulmonary vascular resistance allowing increased antegrade blood flow to the pulmonary artery and improved cardiac output. If tachycardia is not present, isoproterenol administration is recommended in critically ill neonates with anatomically mild Ebstein's anomaly and no associated cardiac defects.