The use of inhaled nitric oxide in a wide variety of clinical problems

Inhaled nitric oxide for the postoperative management of pulmonary hypertension in infants and children with congenital heart disease

BACKGROUND

Nitric oxide (NO) is a prevalent molecule in humans that is responsible for many physiologic activities including pulmonary vasodilation. An exogenous, inhaled form (iNO) exists that mimics this action without affecting systemic blood pressure. This therapy has been implemented in the treatment of pulmonary hypertension. This review examines the efficacy of iNO in the postoperative management of infants and children with congenital heart disease (CHD). The original review was published in 2005, updated in 2008 and again in 2014.

OBJECTIVES

To compare the effects of postoperative administration of iNO versus placebo or conventional management, or both, on infants and children with CHD and pulmonary hypertension. The primary outcome was mortality. Secondary outcomes included length of hospital stay; neurodevelopmental disability; number of pulmonary hypertensive crises (PHTC); changes in mean pulmonary arterial pressure (MPAP), mean arterial pressure (MAP), and heart rate (HR); changes in oxygenation measured as the ratio of arterial oxygen tension (PaO2) to fraction of inspired oxygen (FiO2); and measurement of maximum methaemoglobin level as a marker of toxicity.

SEARCH METHODS

In this updated version we extended the CENTRAL search to 2013, Issue 12 of The Cochrane Library, and MEDLINE and EMBASE through to 1 December 2013. The original search was performed in July 2004 and again in November 2007. We included abstracts and all languages.

SELECTION CRITERIA

We included randomized and quasi-randomized controlled trials comparing iNO with placebo or conventional management, or both. Trials included only children with CHD requiring surgery complicated by pulmonary hypertension.

DATA COLLECTION AND ANALYSIS

Two authors extracted data. Data were collected on mortality; number of PHTC; changes in MPAP, MAP, HR, and PaO2:FiO2; and maximum methaemoglobin level. Data on long-term mortality, neurodevelopmental disability, and length of hospital stay were unavailable. We performed subgroup analysis by method of control (placebo or conventional management).

MAIN RESULTS

We reran the searches to December 2013 and identified three new studies. These three studies did not fulfil our inclusion criteria. Therefore, no new studies were included in this updated review. In total four randomized trials involving 210 participants were included in this review. We observed no differences in mortality (OR 1.67, 95% CI 0.38 to 7.30; P = 0.50); PHTC (OR 0.80, 95% CI 0.15 to 4.18; P = 0.79); changes in MPAP (treatment effect -2.94 mm Hg, 95% CI -9.28 to 3.40; P = 0.36), MAP (treatment effect -3.55 mm Hg, 95% CI -11.86 to 4.76; P = 0.40), HR (treatment effect 0.02 bpm, 95% CI -8.13 to 8.18; P = 1.00), or PaO2:FiO2 (mean difference 17.18, 95% CI -28.21 to 62.57; P = 0.46). There was a significant increase in the methaemoglobin level (mean difference 0.30%, 95% CI 0.24 to 0.36; P < 0.00001) in patients treated with iNO, although levels did not reach toxicity levels. Data from long-term mortality, neurodevelopmental disability, and length of stay were not available. Two trials had a low risk of bias. Very low quality of the evidence was observed considering grading of the outcomes.

AUTHORS' CONCLUSIONS

We observed no differences with the use of iNO in the outcomes reviewed. No data were available for several clinical outcomes including long-term mortality and neurodevelopmental outcome. We found it difficult to draw valid conclusions given concerns regarding methodologic quality, sample size, and heterogeneity.

Gene transfer of endothelial nitric oxide synthase attenuates flow-induced pulmonary hypertension in rabbits

BACKGROUND

Nitric oxide, a potent vasodilator with an important role in the regulation of pulmonary vascular tone, is synthesized by a family of nitric oxide synthases. To determine whether endothelial nitric oxide synthase (eNOS) gene transfer may prevent pulmonary hypertension, the effects of transfer of the eNOS gene to the lung were studied in rabbits with pulmonary hypertension induced by high pulmonary blood flow.

METHODS

Adenoviral vector encoding the eNOS gene was intratracheally transfected into the lung of rabbits with flow-induced pulmonary hypertension. Rabbits instilled intratracheally with adenoviral vector without encoding the eNOS gene served as a control group. Hemodynamic data were recorded before and after transfection, and transgene expression was investigated.

RESULTS

Pulmonary hypertension was significantly attenuated in eNOS gene-transfected rabbits compared with control animals (mean pulmonary arterial pressure, 22.3 +/- 5.5 versus 41.0 +/- 6.9 mm Hg; pulmonary vascular resistance, 326 +/- 42 versus 618 +/- 66 dynes x s x cm(-5); p < 0.01). Systemic arterial pressure and systemic vascular resistance were unaffected. There was an increase in calcium-dependent conversion of L-arginine to L-citrulline in the lung (16.81 +/- 0.72 versus 4.11 +/- 0.41 pmol x mg protein(-1) x h(-1)) and cyclic guanosine monophosphate levels (0.138 +/- 0.015 versus 0.065 +/- 0.003 pmol/mg protein). Immunohistochemical staining showed expression of the eNOS gene was detected mainly in endothelial cells of small pulmonary vessels. Transgene expression was confirmed using Western blot analysis.

CONCLUSIONS

These data suggest that intratracheal adenoviral-mediated eNOS gene transfer can attenuate flow-induced pulmonary hypertension in rabbits and may represent a new form of therapy for the treatment of flow-induced pulmonary hypertension.

Mean airway pressure and response to inhaled nitric oxide in neonatal and pediatric patients

Inhaled nitric oxide (iNO) can improve oxygenation and ventilation-perfusion (V/Q) matching by reduction of shunt (Qs/Qt) in patients with hypoxemic lung disease. Because the improvement in V/Q matching must occur by redistribution of pulmonary blood flow, and because high airway pressure (Paw) increases physiologic dead space (Vd/Vt), we hypothesized that high Paw may limit the improvement in V/Q matching during iNO treatment. iNO 0-50 ppm was administered during mechanical ventilation. Mechanical ventilator settings were at the discretion of the attending physician. Qs/Qt and Vd/Vt were derived from a tripartite lung model with correction for shunt-induced dead space. Data from 62 patients during 153 trials were analyzed for effects of Paw and iNO on Qs/Qt and Vd/Vt. Baseline Qs/Qt was slightly increased at Paw 16-23 cmH2O (p < 0.05), while Vd/Vt increased progressively with higher Paw (p < 0.002). Therapy with iNO significantly reduced Qs/Qt (p < 0.001) at all levels of mean Paw, reaching a maximum reduction at 16-23 cmH2O (p < 0.05), such that Qs/Qt during iNO treatment was similar at all levels of Paw. During iNO treatment, a reduction in Vd/Vt occurred only at Paw of 8-15 cmH2O (p < 0.05), and the positive relationship between Vd/Vt and Paw was maintained. These differential effects on Qs/Qt and Vd/Vt suggest that both high and low Paw may limit improvement in gas exchange with iNO. Analysis of gas exchange using this corrected tripartite lung model may help optimize ventilatory strategies during iNO therapy.

Cardiovascular drugs for the newborn

This article reviews the various cardiovascular drugs for newborns, including antiarrhythmics, antihypertensives, inotropes, and pulmonary vasodilators. Antiarrhythmic drugs are classified according to their mechanisms of action, such as effects on ion channels, duration of repolarization, and receptor interaction, which help with understanding the effects of individual antiarrhythmic drugs and selection of drugs for specific arrhythmias. Drug treatment for hypertension should start with a single drug from one of the following classes: ACE inhibitors, angiotensin-receptor antagonists, beta-receptor antagonists, calcium channel blockers, or diuretics. The inotropic drug should be selected according to its specific pharmacologic properties and the specific cardiovascular abnormality to be corrected. An effective pulmonary vasodilator must dilate the pulmonary vasculature more than the systemic vasculature.

Inhaled nitric oxide for the postoperative management of pulmonary hypertension in infants and children with congenital heart disease

BACKGROUND

Nitric oxide (NO) is a prevalent molecule in the human body responsible for many physiologic activities including pulmonary vasodilation. An exogenous, inhaled form (iNO) exists that mimics this action without directly affecting systemic blood pressure. This therapy has been implemented in the treatment of pulmonary hypertension. This review examines the efficacy of iNO in the postoperative management of infants and children with congenital heart disease.

OBJECTIVES

To compare the effects of postoperative iNO versus placebo and/or conventional management on infants and children with congenital heart disease. The primary outcome was mortality, while secondary outcomes included length of hospital stay, assessment of neurodevelopmental disability, number of pulmonary hypertensive crises (PHTC), changes in haemodynamics including mean pulmonary arterial pressure (MPAP), mean arterial pressure (MAP), and heart rate (HR), changes in oxygenation measured as the ratio PaO2:FiO2, and measurement of maximum methaemoglobin level as a marker of toxicity.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 3, 2004), MEDLINE (1966 to 2004), and EMBASE (1980 to 2004). We included abstracts and all languages.

SELECTION CRITERIA

We included randomized and quasi-randomized controlled trials comparing iNO with placebo and conventional management, or both. Trials included only children with congenital heart disease requiring surgery and complicated by pulmonary hypertension.

DATA COLLECTION AND ANALYSIS

Data were collected on mortality, number of PHTC, changes in MPAP, MAP, HR, and PaO2:FiO2, and maximum methaemoglobin level, while data on long-term mortality, neurodevelopmental disability, and length of hospital stay were unavailable. We performed subgroup analysis by age and method of control. We performed sensitivity analysis using studies of highest methodologic quality.

MAIN RESULTS

We included four randomized trials. We observed no differences between groups with respect to mortality (P = 0.50), PHTC (P = 0.79), change in MPAP (P = 0.16), MAP (P = 0.40), HR (P = 1.00), or PaO2:FiO2 (P = 0.46). There was a significant reduction in MPAP in the subgroup of patients from birth to three months (P = 0.005), although this finding was based on a small number of patients (N = 23).

AUTHORS' CONCLUSIONS

We observed no differences with the use of iNO as compared with control in the majority of outcomes reviewed. No data were available for analysis with respect to several clinical outcomes including long-term mortality and neurodevelopmental outcome. We found it difficult to draw valid conclusions because of concerns regarding methodologic quality, bias, sample size, and heterogeneity.

Gene transfer with inducible nitric oxide synthase decreases production of urea by arginase in pulmonary arterial endothelial cells

Nitric oxide (NO) is a vasodilator produced from L-arginine (L-Arg) by NO synthase (NOS). Gene therapy for hypertensive disorders has been proposed using the inducible isoform of NOS (iNOS). L-Arg also can be metabolized to urea and L-ornithine (L-Orn) by arginase, and L-Orn can be metabolized to proline and/or polyamines, which are vital for cellular proliferation. To determine the effect of iNOS gene transfer on arginase, we transfected bovine pulmonary arterial endothelial cells (bPAEC) with an adenoviral vector containing the gene for iNOS (AdiNOS). As expected, NO production in AdiNOS bPAEC was substantially greater than in control bPAEC. Although urea production was significantly less in the AdiNOS bPAEC than in the control bPAEC, despite similar levels of arginase I protein, AdiNOS transfection of bPAEC had no effect on the uptake of L-Arg. Inhibiting NO production with Nomega-nitro-L-arginine methyl ester increased urea production, and inhibiting urea production with L-valine increased nitrite production, in AdiNOS bPAEC. The addition of L-Arg to the medium increased urea production by AdiNOS bPAEC in a concentration-dependent manner. Thus, in these iNOS-transfected bPAEC, the transfected iNOS and native arginase compete for a common intracellular pool of L-Arg. This competition for substrate resulted in impaired proliferation in the AdiNOS-transfected bPAEC. These findings suggest that the use of iNOS gene therapy for pulmonary hypertensive disorders may not only be beneficial through NO-mediated pulmonary vasodilation but also may decrease vascular remodeling by limiting L-Orn production by native arginase.

The effect of inhaled nitric oxide and oxygen on the hydroxylation of salicylate in rat lungs

Inhaled nitric oxide (iNO) is used as a selective pulmonary vasodilator, and often under conditions when a high fraction of inspired oxygen is indicated. However, little is known about the potential toxicity of iNO therapy with or without concomitant oxygen therapy. NO can combine with superoxide (O2-) to form peroxynitrite (ONOO-), which can in turn decompose to form hydroxyl radical (OH.). Both OH. and ONOO- are involved in various forms of lung injury. To begin evaluation of the effect of iNO under either normoxic or hyperoxic conditions on OH. and/or ONOO- formation, rats were exposed for 58 h to either 21% O2, 21% O2 + 10 parts per million (ppm) NO, 21% O2 + 100 ppm NO, 50% O2, 90% O2, 90% O2 + 10 ppm NO, or 90% O2 + 100 ppm NO. We used a salicylate hydroxylation assay to detect the effects of these exposures on lung OH. and/or ONOO- formation measured as the appearance of 2,3-dihydroxybenzoic acid (2,3-DHBA). Exposure to 90% O2 and 90% O2 + 100 ppm NO resulted in significantly (p < 0.05) greater lung wet weight (1.99 +/- 0.14 g and 3.14 +/- 0.30 g, respectively) compared with 21% O2 (1.23 +/- 0.01 g). Exposure to 21% O2 + 100 ppm NO led to 2.5 times the control (21% O2 alone) 2,3 DHBA formation (p < 0.05) and exposure to 90% O2 led to 2.4 times the control 2,3-DHBA formation (p < 0.05). However, with exposure to both 90% O2 and 100 ppm NO, the 2,3-DHBA formation was no greater than the control condition (21% O2). Thus, these results indicate that, individually, both the hyperoxia and the 100 ppm NO led to greater salicylate hydroxylation, but that the combination of hyperoxia and 100 ppm NO led to less salicylate hydroxylation than either did individually. The production of OH. and/or ONOO- in the lung during iNO therapy may depend on the ratio of NO to O2.

Nitric oxide donors and cardiovascular agents modulating the bioactivity of nitric oxide: an overview

Nitric oxide (NO) mediates multiple physiological and pathophysiological processes in the cardiovascular system. Pharmacological compounds that release NO have been useful tools for evaluating the pivotal role of NO in cardiovascular physiology and therapeutics. These agents constitute two broad classes of compounds, those that release NO or one of its redox congeners spontaneously and those that require enzymatic metabolism to generate NO. In addition, several commonly used cardiovascular drugs exert their beneficial action, in part, by modulating the NO pathway. Here, we review these classes of agents, summarizing their fundamental chemistry and pharmacology, and provide an overview of their cardiovascular mechanisms of action.

Regulation of anion secretion by nitric oxide in human airway epithelial cells

Nitric oxide (NO) is continuously produced and released in human airways, but the biological significance of this process is unknown. In this study, we have used Calu-3 cells to investigate the effects of NO on transepithelial anion secretion. An inhibitor of NO synthase, NG-nitro-L-arginine methyl ester, reduced short- circuit current (I(sc)), whereas an NO donor, S-nitrosoglutathione (GSNO), increased I(sc), with an EC50 approximately 1.2 microM. The NO-activated current was inhibited by diphenylamine-2-carboxylate, clotrimazole, and charybdotoxin. Selective permeabilization of cell membranes indicated that NO activated both apical anion channels and basolateral potassium channels. An inhibitor of soluble guanylate cyclase, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, prevented activation of I(sc) by NO but not by 8-bromo-cGMP, suggesting that NO acts via a cGMP-dependent pathway. Sequential treatment of cells with forskolin and GSNO or 1-ethyl-2-benzimidazolinone and GSNO showed additive effects of these chemicals on I(sc). Interestingly, GSNO elevated intracellular Ca2+ concentration ([Ca2+]i) but had no effect on I(sc) activated by thapsigargin. These results show that NO activates transepithelial anion secretion via a cGMP-dependent pathway that involves cross talk between NO and [Ca2+]i.

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.

Nitric oxide and postangioplasty restenosis: pathological correlates and therapeutic potential

Balloon angioplasty revolutionized interventional cardiology as a nonsurgical procedure to clear a diseased artery of atherosclerotic blockage. Despite its procedural reliability, angioplasty's long-term outcome can be compromised by restenosis, the recurrence of arterial blockage in response to balloon-induced vascular trauma. Restenosis constitutes an important unmet medical need whose pathogenesis has yet to be understood fully and remains to be solved therapeutically. The radical biomediator, nitric oxide (NO), is a natural modulator of several processes contributing to postangioplasty restenosis. An arterial NO deficiency has been implicated in the establishment and progression of restenosis. Efforts to address the restenosis problem have included trials evaluating a wide range of NO-based interventions for their potential to inhibit balloon-induced arterial occlusion. All types of NO-based interventions yet investigated benefit at least one aspect of balloon injury to a naive vessel in a laboratory animal without inducing significant side effects. The extent to which this positive, albeit largely descriptive, body of experimental data can be translated into the clinic remains to be determined. Further insight into the pathogenesis of restenosis and the molecular mechanisms by which NO regulates vascular homeostasis would help bridge this gap. At present, NO supplementation represents a unique and potentially powerful approach to help control restenosis, either alone or as a pharmaceutical adjunct to a vascular device.

Inhaled nitric oxide selectively dilates pulmonary vasculature in adult patients with pulmonary hypertension, irrespective of etiology

OBJECTIVES

We sought to compare the responses of patients with pulmonary hypertension from primary and secondary causes (PPH and SPH, respectively) to inhaled nitric oxide (iNO) in the cardiac catheterization laboratory.

BACKGROUND

Pulmonary hypertension can lead to right ventricular pressure overload and failure. Although vasodilators are effective as therapy in patients with PPH, less is known about their role in adults with SPH. Inhaled nitric oxide can accurately predict the response to other vasodilators in PPH and could be similarly utilized in SPH.

METHODS

Forty-two patients (26 to 77 years old) with pulmonary hypertension during cardiac catheterization received iNO. Demographic and hemodynamic data were collected. Their response to iNO was defined by a decrease of > or =20% in mean pulmonary artery (PA) pressure or pulmonary vascular resistance (PVR).

RESULTS

Mean PA pressures and PVR were lower during nitric oxide (NO) inhalation in all patients with pulmonary hypertension. Seventy-eight percent of patients with PPH and 83% of patients with SPH were responders to iNO. A trend was seen toward a greater response with larger doses of NO in patients with SPH. Nitric oxide was a more sensitive predictor of response (79%), compared with inhaled oxygen (64%), and was well tolerated, with no evidence of systemic effects. Elevation in right ventricular end-diastolic pressure appeared to predict poor vasodilatory response to iNO.

CONCLUSIONS

Nitric oxide is a safe and effective screening agent for pulmonary vasoreactivity. Regardless of etiology of pulmonary hypertension, pulmonary vasoreactivity is frequently demonstrated with the use of NO. Right ventricular diastolic dysfunction may predict a poor vasodilator response.

Combined-modality therapy with inhaled nitric oxide and exogenous surfactant in term infants with acute respiratory failure

OBJECTIVE

To report cases of neonates successfully treated with both exogenous surfactant and inhaled nitric oxide (INO).

DESIGN

Retrospective chart review of full term infants treated between January and May 1999 in the neonatal intensive care unit of The Children's Hospital at Strong, University of Rochester, Rochester, New York.

PATIENTS

Three full-term infants treated with surfactant and INO were identified. Each infant had severe acute respiratory failure (as a result of severe aspiration syndromes) and a clinical diagnosis of pulmonary hypertension and parenchymal lung disease in the absence of congenital malformations.

INTERVENTIONS

One infant received INO (20-40 ppm) followed by exogenous surfactant (100mg/kg); the other two received surfactant followed by INO.

MAIN RESULTS

All three infants exhibited a favorable response to treatment with these agents in terms of improved arterial oxygenation as summarized by oxygenation index and all survived to discharge home without referral for extracorporeal membrane oxygenation.

CONCLUSIONS

No adverse interactions were observed related to INO plus surfactant therapy. The responses of these critically ill infants were consistent with the hypothesis that the actions of INO in dilating the pulmonary microvasculature and of exogenous surfactant in stabilizing and recruiting alveoli are complementary and may lead to additive clinical benefits. These case results suggest that more extensive clinical studies are warranted for combined-modality therapy with INO and exogenous surfactant in patients with the acute respiratory distress syndrome.

Combination therapy with inhaled nitric oxide and intravenous dobutamine during pulmonary hypertension in the rabbit

Combination therapy with an intravenous inovasodilator and inhaled nitric oxide (NO) may be appropriate in patients with pulmonary hypertension and associated right ventricular failure. We examined whether dobutamine and inhaled NO would have additive pulmonary vasodilator effects in experimental pulmonary hypertension. Pulmonary hypertension was produced in anesthetized, mechanically ventilated rabbits by infusion of U46619, a thromboxane analogue. Dobutamine was administered in increasing doses (2.5-20 microg/kg/min) with and without inhaled NO (40 ppm). Dobutamine produced dose-dependent decreases in pulmonary vascular resistance (PVR) and mean arterial pressure (MAP) and increases in cardiac output (CO). Inhaled NO alone decreased pulmonary artery pressure (PAP) and PVR with no effect on MAP or CO. The effects of dobutamine and inhaled NO were additive, so that at each dose of dobutamine, inhaled NO decreased PAP and PVR with no effect on systemic hemodynamics. This study suggests that the combination of dobutamine and inhaled NO should produce additive pulmonary vasodilation in patients with pulmonary hypertension and associated right ventricular dysfunction.

Nitric oxide (NO)-related pharmaceuticals: contemporary approaches to therapeutic NO modulation

The biologically important gaseous radical, nitric oxide (NO), is a versatile chemical entity that enters into regulatory, protective, and adverse interactions with biomolecules and cells, in some cases through NO-derived nitrogen oxide species. Both excess tissue NO and its insufficiency have been implicated in the genesis or evolution of several important disease states. The associated medical needs and commercial opportunities have fostered attempts to modulate tissue NO tone for symptomatic benefit or therapeutic gain. State-of-the-art strategies for NO modulation in contemporary drug discovery and development encompass sexual dysfunction, cardiovascular, and antiinflammatory indications. Increased understanding of NO's physiological chemistry and ways to target its pharmacology appear critical to the successful clinical exploitation of NO's diverse properties. Integration of research on both the basic science of NO's mechanistic biology and the applied science of drug discovery and development represents a millennium mandate to the pharmaceutical industry in the area of NO-related therapeutics.