Rebound pulmonary hypertension on withdrawal from inhaled nitric oxide

High Frequency Oscillatory Ventilation (HFOV) and Inhaled Nitric Oxide (iNO) Use During Neonatal Emergency Transport - Feasibility and Efficacy in India

A retrospective study of 24 neonates to evaluate the feasibility and efficacy of high frequency oscillatory ventilation (HFOV) and inhaled nitric oxide (iNO) for transferring critically ill neonates to tertiary neonatal intensive care, who were transported by road ambulance was done. Efficacy was measured by clinical improvement, patient safety was assessed by comparing cardiorespiratory indicators before and after transport, and adverse events during transport. Significant oxygenation improvement was observed in neonates transported with HFOV ± iNO compared to earlier ventilator settings. Pre- and post-transport vital signs were stable, and no transport-related deaths occurred. A substantial rise in median SpO2 was seen after transfer [86 (81, 91) vs. 93 (89, 97) before transport, p <0.001]. Twelve of twenty-one newborns who received nitric oxide demonstrated significant improvement in oxygenation index (a 10% decrease from prior value). Overall survival was 70.8%, however non-transfer or inadequate respiratory treatment may have exacerbated mortality.

Real-world safety and effectiveness of inhaled nitric oxide therapy for pulmonary hypertension during the perioperative period of cardiac surgery: a post-marketing study of 2817 patients in Japan

OBJECTIVE

To evaluate the real-world safety and effectiveness of inhaled nitric oxide (INOflo® for Inhalation 800 ppm) for perioperative pulmonary hypertension associated with cardiac surgery in Japan.

METHODS

This was a prospective, non-interventional, all-case, post-marketing study of pediatric and adult patients who received perioperative INOflo with cardiac surgery from November 2015-December 2020. Safety and effectiveness were monitored from INOflo initiation to 48 h after treatment completion or withdrawal. Safety outcomes included adverse drug reactions, blood methemoglobin concentrations, and inspired nitrogen dioxide concentrations over time. Effectiveness outcomes included changes in central venous pressure among pediatrics, mean pulmonary arterial pressure among adults, and the partial pressure of arterial oxygen/fraction of inspired oxygen ratio (PaO2/FiO2) in both populations.

RESULTS

The safety analysis population included 2,817 Japanese patients registered from 253 clinical sites (pediatrics, n = 1375; adults, n = 1442). INOflo was generally well tolerated; 15 and 20 adverse drug reactions were reported in 14 pediatrics (1.0%) and 18 adults (1.2%), respectively. No clinically significant elevations in blood methemoglobin and inspired nitrogen dioxide concentrations were observed. INOflo treatment was associated with significant reductions in both central venous pressure among pediatrics and mean pulmonary arterial pressure among adults, and significant improvements in PaO2/FiO2 among pediatrics and adults with PaO2/FiO2 ≤ 200 at baseline.

CONCLUSIONS

Perioperative INOflo treatment was a safe and effective strategy to improve hemodynamics and oxygenation in patients with pulmonary hypertension during cardiac surgery. These data support the use of INOflo for this indication in Japanese clinical practice.

Inhaled NO at a crossroads in cardiac surgery: current need to improve mechanistic understanding, clinical trial design and scientific evidence

Inhaled nitric oxide (NO) has been used in pediatric and adult perioperative cardiac intensive care for over three decades. NO is a cellular signaling molecule that induces smooth muscle relaxation in the mammalian vasculature. Inhaled NO has the unique ability to exert its vasodilatory effects in the pulmonary vasculature without any hypotensive side-effects in the systemic circulation. In patients undergoing cardiac surgery, NO has been reported in numerous studies to exert beneficial effects on acutely lowering pulmonary artery pressure and reversing right ventricular dysfunction and/or failure. Yet, various investigations failed to demonstrate significant differences in long-term clinical outcomes. The authors, serving as an advisory board of international experts in the field of inhaled NO within pediatric and adult cardiac surgery, will discuss how the existing scientific evidence can be further improved. We will summarize the basic mechanisms underlying the clinical applications of inhaled NO and how this translates into the mandate for inhaled NO in cardiac surgery. We will move on to the popular use of inhaled NO and will talk about the evidence base of the use of this selective pulmonary vasodilator. This review will elucidate what kind of clinical and biological barriers and gaps in knowledge need to be solved and how this has impacted in the development of clinical trials. The authors will elaborate on how the optimization of inhaled NO therapy, the development of biomarkers to identify the target population and the definition of response can improve the design of future large clinical trials. We will explain why it is mandatory to gain an international consensus for the state of the art of NO therapy far beyond this expert advisory board by including the different major players in the field, such as the different medical societies and the pharma industry to improve our understanding of the real-life effects of inhaled NO in large scale observational studies. The design for future innovative randomized controlled trials on inhaled NO therapy in cardiac surgery, adequately powered and based on enhanced biological phenotyping, will be crucial to eventually provide scientific evidence of its clinical efficacy beyond its beneficial hemodynamic properties.

Safety of inhaled nitric oxide withdrawal in severe chronic pulmonary hypertension

Inhaled nitric oxide (iNO) is a potent and selective pulmonary vasodilator with a safety concern due to rebound pulmonary hypertension (PH) associated with its withdrawal. We report short-term pulsed iNO in patients with severe pulmonary arterial hypertension (PAH) and nonoperable chronic thromboembolic PH (nCTEPH). This is a retrospective analysis of 33 patients: 22 with PAH and 11 with nCTEPH. We assessed hemodynamic, echocardiographic, and other noninvasive variables to evaluate safety and efficacy of iNO. We performed an iNO withdrawal test during right heart catheterization and after 3 days of iNO treatment. iNO significantly improved all variables examined in 22 patients with PAH and 11 with nCTEPH. Two patterns of response were observed after sudden iNO withdrawal. Twenty-nine patients (88%) showed minimal hemodynamic, oxygenation and clinical changes. Four patients (12%) had a reduction in cardiac index ≥20% and PaO2 ≥ 5%, three patients did not show clinical deterioration, and one patient developed hemodynamic collapse that needed iNO administration. This retrospective study suggests that short-term iNO improves hemodynamics and clinical conditions in some patients with PAH an nCTPEH. However, pulsed iNO withdrawal PH rebound could be a serious concern in these patients. Given the lack of evidence, we do not recommend the use of pulsed iNO in the treatment of patients with chronic PH.

Compatibility and Safety Implications Associated with Interfacing Medical Devices in Neonatal Respiratory Care: A Case Example Using the Inhaled Nitric Oxide Delivery System

Over the past decade, international organizations have instituted strict regulations for the safe use of connected medical devices. The International Organization for Standardization and the Medical Device Single Audit Program instituted certifications to ensure that connected devices are compatible and operate within their proper clinical parameters. These efforts came about, in part, as a consequence of clinicians’ decisions to use nonstandard, modified, or improvised devices for purposes outside the original manufacturers’ approved parameters. Unapproved device modifications can be associated with increased risk of dosing errors, monitoring errors, tubing misconnections and serious or potentially fatal adverse events; furthermore, health care providers who implement unapproved device modifications may assume legal and financial liability should harm come to patients as a consequence of the modification. Using the inhaled nitric oxide delivery system as an example, the objective of this paper is to raise awareness of the potential dangers associated with unapproved modification and interfacing of therapeutic gas delivery systems and ventilators in the neonatal intensive care unit setting. The paper also highlights the rationale and necessity for rigorous validation processes that ensure that interfaced medical devices perform as intended in the clinical setting.

Droplet Size and Distribution of Nebulized 3% Sodium Chloride, Albuterol, and Epoprostenol by Phase Doppler Particle Analyzer

Background

Aerosolized drug therapy administered to mechanically ventilated patients is a standard part of pulmonary critical care medicine. Aerosol particle size and distribution are important factors in the optimal delivery of aerosolized drugs to ventilated patients.

Objective

The objective of this study was to characterize aerosol droplet size and distribution with laser diffraction for nebulized 3% sodium chloride, albuterol, and epoprostenol sodium (containing glycine) delivered via Aeroneb Solo Mesh Nebulizers (Aerogen, Mountain View, California).

Methods

A series of functional flow tests were run on each of 8 Solo mesh nebulizers before the study to verify accuracy of flow rates in milliliters per minute. Aerosolized droplets exiting the nebulizer heads were then measured using a phase Doppler particle analyzer. Data collected during delivery of 3% sodium chloride, albuterol, and epoprostenol sodium included aerosol droplet size distribution, mass median aerodynamic diameter (MMAD), and geometric standard deviation. For each Solo nebulizer, droplet size measurements were taken 2 cm away from the nebulizer head and 2 cm away from the wye of a heated, humidified adult ventilator circuit. For measurements taken at the wye, 4 distinct, continuous flow rates (2, 10, 20, and 40 L/min) were generated by an air pump to simulate inspiratory flows delivered with mechanical ventilation. The expiratory limb was capped, and the nebulizer head was inserted into the breathing circuit upstream of the humidifier.

Results

Each Solo nebulizer met Aerogen's recommended minimum flow rate of 0.2 mL/min, ranging from 0.23 to 0.31 mL/min. The MMAD of the 3 tested aerosols was several times smaller when measured at the wye outlet of the heated/humidified breathing circuit (0.82–2.73 µm) compared with droplets measured directly at the nebulizer outlet (MMAD, 4.6–7.3 µm). There was also significant variability across Solo heads with some ventilator flow rates. The mean MMAD at the wye for the 3% sodium chloride solution, albuterol, and epoprostenol test solutions was 1.62 µm, 1.09 µm, and 1.18 µm, respectively. The mean MMAD at the nebulizer for the 3% sodium chloride solution, albuterol, and epoprostenol test solutions was 5.37 µm, 5.73 µm, and 6.73 µm, respectively.

Conclusions

Results from this study suggest that particle size of aerosolized drugs administered via a commonly used setup for delivery of in-line aerosols to mechanically ventilated patients may be several times smaller than expected and may result in less drug being delivered to the patient than previously realized.

(Curr Ther Res Clin Exp. 2021; 82:XXX–XXX)

© 2021 Elsevier HS Journals, Inc.

Rationale for Use of an FDA-Cleared Delivery System for Administration of Inhaled Nitric Oxide in Patients Undergoing Magnetic Resonance Imaging

Inhaled nitric oxide (iNO) is a pulmonary vasodilator approved for use to improve lung function in neonates >34 weeks' gestational age with hypoxic respiratory failure and pulmonary hypertension. Infants with severe respiratory disease frequently require magnetic resonance imaging (MRI) scans for evaluation of treatment and diagnosis of concurrent disease processes. Until 2015, incompatibility between the standard iNO delivery system components and the magnetic field within the MRI setting required iNO treatment to be interrupted for MRI, which could increase risk of deoxygenation and rebound pulmonary hypertension. In some cases, patients had to forego or delay MRI in order to maintain uninterrupted iNO delivery. The US Food and Drug Administration cleared the first iNO delivery system specifically modified for conditional use with MRI scanners (INOmax DS_IR ^® Plus MRI) in 2015, based on the determination that the MRI-cleared system met the performance standards equivalent to the standard system. The system design and manufacturer risk management activities, as well as the regulatory requirements for clearance and continued use, provide necessary safeguards to ensure that high-risk neonates receive uninterrupted iNO in a safe manner. Anecdotal reports suggest that adoption of the MRI-cleared system may help optimize care for critically ill neonates who require concurrent administration of iNO and MRI scanning. Further research will be necessary to quantify the nature and magnitude of clinical improvements associated with adoption of the MRI iNO delivery system.

Endothelial shear stress enhancements: a potential solution for critically ill Covid-19 patients

Most critically ill Covid-19 patients succumb to multiple organ failure and/or sudden cardiac arrest (SCA) as a result of comorbid endothelial dysfunction disorders which had probably aggravated by conventional mechanical assist devices. Even worse, mechanical ventilators prevent the respiratory pump from performing its crucial function as a potential generator of endothelial shear stress (ESS) which controls microcirculation and hemodynamics since birth. The purpose of this work is to bring our experience with ESS enhancement and pulmonary vascular resistance (PVR) management as a potential therapeutic solution in acute respiratory distress syndrome (ARDS). We propose a non-invasive device composed of thoracic and infradiaphragmatic compartments that will be pulsated in an alternating frequency (20/40 bpm) with low-pressure pneumatic generator (0.1–0.5 bar). Oxygen supply, nasogastric with, or without endotracheal tubes are considered.

Vasoconstrictor Mechanisms in Chronic Hypoxia-Induced Pulmonary Hypertension: Role of Oxidant Signaling

Elevated resistance of pulmonary circulation after chronic hypoxia exposure leads to pulmonary hypertension. Contributing to this pathological process is enhanced pulmonary vasoconstriction through both calcium-dependent and calcium sensitization mechanisms. Reactive oxygen species (ROS), as a result of increased enzymatic production and/or decreased scavenging, participate in augmentation of pulmonary arterial constriction by potentiating calcium influx as well as activation of myofilament sensitization, therefore mediating the development of pulmonary hypertension. Here, we review the effects of chronic hypoxia on sources of ROS within the pulmonary vasculature including NADPH oxidases, mitochondria, uncoupled endothelial nitric oxide synthase, xanthine oxidase, monoamine oxidases and dysfunctional superoxide dismutases. We also summarize the ROS-induced functional alterations of various Ca2+ and K+ channels involved in regulating Ca2+ influx, and of Rho kinase that is responsible for myofilament Ca2+ sensitivity. A variety of antioxidants have been shown to have beneficial therapeutic effects in animal models of pulmonary hypertension, supporting the role of ROS in the development of pulmonary hypertension. A better understanding of the mechanisms by which ROS enhance vasoconstriction will be useful in evaluating the efficacy of antioxidants for the treatment of pulmonary hypertension.

Combined Spinal and Epidural Anaesthesia for Caesarean Section in a Parturient with Severe Primary Pulmonary Hypertension

We describe the management of a parturient with severe primary pulmonary hypertension who underwent caesarean section. A multi-disciplinary approach was used. She was admitted to the intensive care unit perioperatively for invasive monitoring and trial of inhaled nitric oxide. Anaesthesia was provided by combined spinal-epidural block. We discuss controversies about the management of obstetric patients with this rare and serious condition.

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.

A retrospective comparison of inhaled milrinone and iloprost in post-bypass pulmonary hypertension

During cardiac operations, weaning from cardiopulmonary bypass (CPB) may prove challenging as a result of superimposed acute right ventricular dysfunction in the setting of elevated pulmonary vascular resistance (PVR). The aim of this study was to retrospectively evaluate the effect of inhaled milrinone versus inhaled iloprost in patients with persistent pulmonary hypertension following discontinuation of CPB. Eighteen patients with elevated PVR post-bypass were administered inhaled milrinone at a cumulative dose of 50 μg kg-1. These patients were retrospectively matched with 18 patients who were administered 20 μg of inhaled iloprost. Both drugs were administered through a disposable aerosol-generating jet nebulizer device and inhaled for a 15-min period. Hemodynamic measurements were performed before and after cessation of the inhalation period. Both inhaled milrinone and inhaled iloprost induced significant reductions in mean pulmonary artery pressure and PVR and significant increases in cardiac index in patients with post-CPB pulmonary hypertension. The favorable effect of both agents on the pulmonary vasculature was confirmed by echocardiographic measurements. Both agents were devoid of systemic side effects, since mean arterial pressure and systemic vascular resistance were not affected. A decrease in intrapulmonary shunt by inhalation of both agents was also demonstrated. Pulmonary vasodilatation attributed to iloprost seems to be of greater magnitude and of longer duration as compared to that of inhaled milrinone. Both substances proved to be selective pulmonary vasodilators. The greater magnitude and of longer duration vasodilatation attributed to iloprost may be due to its longer duration of action.

Inhaled nitric oxide therapy for pulmonary disorders of the term and preterm infant

The 21st century began with the FDA approval of inhaled nitric oxide therapy for the treatment of neonatal hypoxic respiratory failure associated with pulmonary hypertension in recognition of the 2 randomized clinical trials demostrating a significant reduction in the need for extracorporeal support in the term and near-term infant. Inhaled nitric oxide is one of only a few therapeutic agents approved for use through clinical investigations primarily in the neonate. This article provides an overview of the pertinent biology and chemistry of nitric oxide, discusses potential toxicities, and reviews the results of pertinent clinical investigations and large randomized clinical trials including neurodevelopmental follow-up in term and preterm neonates. The clinical investigations conducted by the Eunice Kennedy Shriver NICHD Neonatal Research Network will be discussed and placed in context with other pertinent clinical investigations exploring the efficacy of inhaled nitric oxide therapy in neonatal hypoxic respiratory failure.

Inhaled pulmonary vasodilators for persistent pulmonary hypertension of the newborn: safety issues relating to drug administration and delivery devices

Treatment for persistent pulmonary hypertension of the newborn (PPHN) aims to reduce pulmonary vascular resistance while maintaining systemic vascular resistance. Selective pulmonary vasodilation may be achieved by targeting pulmonary-specific pathways or by delivering vasodilators directly to the lungs. Abrupt withdrawal of a pulmonary vasodilator can cause rebound pulmonary hypertension. Therefore, use of consistent delivery systems that allow for careful monitoring of drug delivery is important. This manuscript reviews published studies of inhaled vasodilators used for treatment of PPHN and provides an overview of safety issues associated with drug delivery and delivery devices as they relate to the risk of rebound pulmonary hypertension. Off-label use of aerosolized prostacyclins and an aerosolized prostaglandin in neonates with PPHN has been reported; however, evidence from large randomized clinical trials is lacking. The amount of a given dose of aerosolized drug that is actually delivered to the lungs is often unknown, and the actual amount of drug deposited in the lungs can be affected by several factors, including patient size, nebulizer used, and placement of the nebulizer within the breathing circuit. Inhaled nitric oxide (iNO) is the only pulmonary vasodilator approved by the US Food and Drug Administration for the treatment of PPHN. The iNO delivery device, INOmax DS_IR®IR, is designed to constantly monitor NO, NO₂, and O₂ deliveries and is equipped with audible and visual alarms to alert providers of abrupt discontinuation and incorrect drug concentration. Other safety features of this device include two independent backup delivery systems, a backup drug cylinder, a battery that provides up to 6 hours of uninterrupted medication delivery, and 27 alarms that monitor delivery, dosage, and system functions. The ability of the drug delivery device to provide safe, consistent dosing is important to consider when selecting a pulmonary vasodilator.

Liposomal Aerosols of Nitric Oxide (NO) Donor as a Long-Acting Substitute for the Ultra-Short-Acting Inhaled NO in the Treatment of PAH

PURPOSE

This study seeks to develop a liposomal formulation of diethylenetriamine NONOate (DN), a long acting nitric oxide (NO) donor, with a goal to replace inhaled NO (iNO) in the treatment of pulmonary arterial hypertension (PAH).

METHODS

Liposomal formulations were prepared by a lipid film hydration method and modified with a cell penetrating peptide, CAR. The particles were characterized for size, polydispersity index (PDI), zeta potential, entrapment efficiency, storage and nebulization stability, and in-vitro release profiles. The cellular uptake and transport were assessed in rat alveolar macrophages (NR8383) and transforming growth factor β (TGF-β) activated rat pulmonary arterial smooth muscle cells (PASMCs). The fraction of the formulation that enters the systemic circulation, after intratracheal administration, was determined in an Isolated Perfused Rat Lung (IPRL) model. The safety of the formulations were assessed using an MTT assay and by measuring injury markers in the bronchoalveolar lavage (BAL) fluid; the pharmacological efficacy was evaluated by monitoring the changes in the mean pulmonary arterial (mPAP) and systemic pressure (mSAP) in a monocrotaline (MCT) induced-PAH rat model

RESULTS

Liposome size, zeta potential, and entrapment efficiency were 171 ± 4 nm, -37 ± 3 mV, and 46 ± 5%, respectively. The liposomes released 70 ± 5% of the drug in 8 h and were stable when stored at 4°C. CAR-conjugated-liposomes were taken up more efficiently by PASMCs than liposomes-without-CAR; the uptake of the formulations by rat alveolar macrophages was minimal. DN-liposomes did not increase lung weight, protein quantity, and levels of injury markers in the BAL fluid. Intratracheal CAR-liposomes reduced the entry of liposomes from the lung to blood; the formulations produced a 40% reduction in mPAP for 180 minutes.

CONCLUSION

This study establishes the proof-of-concept that peptide modified liposomal formulations of long-acting NO donor can be an alternative to short-acting iNO.

Inhaled nitric oxide decreases pulmonary endothelial nitric oxide synthase expression and activity in normal newborn rat lungs

Inhaled nitric oxide (iNO) is commonly used in the treatment of very ill pre-term newborns. Previous studies showed that exogenous NO could affect endothelial NO synthase (eNOS) activity and expression in vascular endothelial cell cultures or adult rat models, but this has never been fully described in newborn rat lungs. We therefore aimed to assess the effects of iNO on eNOS expression and activity in newborn rats.

Rat pups, post-natal day (P) 0 to P7, and their dams were placed in a chamber containing NO at 5 ppm (iNO-5 ppm group) or 20 ppm (iNO-20 ppm group), or in room air (control group). Rat pups were sacrificed at P7 and P14 for evaluation of lung eNOS expression and activity.

At P7, eNOS protein expression in total lung lysates, in bronchial and arterial sections, was significantly decreased in the iNO-20 ppm versus control group. At P14, eNOS expression was comparable among all three groups. The amounts of eNOS mRNA significantly differed at P7 between the iNO-20 ppm and control groups. NOS activity decreased in the iNO-20 ppm group at P7 and returned to normal levels at P14. There was an imbalance between superoxide dismutase and NOS activities in the iNO-20 ppm group at P7.

Inhalation of NO at 20 ppm early after birth decreases eNOS gene transcription, protein expression and enzyme activity. This decrease might account for the rebound phenomenon observed in patients treated with iNO.

Inhaled NO decreases endogenous NO synthesis and favours rebound pulmonary hypertension after inhaled NO withdrawalhttp://ow.ly/WNDq2

Pediatric Pulmonary Hypertension: Guidelines From the American Heart Association and American Thoracic Society

Pulmonary hypertension is associated with diverse cardiac, pulmonary, and systemic diseases in neonates, infants, and older children and contributes to significant morbidity and mortality. However, current approaches to caring for pediatric patients with pulmonary hypertension have been limited by the lack of consensus guidelines from experts in the field. In a joint effort from the American Heart Association and American Thoracic Society, a panel of experienced clinicians and clinician-scientists was assembled to review the current literature and to make recommendations on the diagnosis, evaluation, and treatment of pediatric pulmonary hypertension. This publication presents the results of extensive literature reviews, discussions, and formal scoring of recommendations for the care of children with pulmonary hypertension.

Perioperative pharmacological management of pulmonary hypertensive crisis during congenital heart surgery

Pulmonary hypertensive crisis is an important cause of morbidity and mortality in patients with pulmonary arterial hypertension secondary to congenital heart disease (PAH-CHD) who require cardiac surgery. At present, prevention and management of perioperative pulmonary hypertensive crisis is aimed at optimizing cardiopulmonary interactions by targeting prostacyclin, endothelin, and nitric oxide signaling pathways within the pulmonary circulation with various pharmacological agents. This review is aimed at familiarizing the practitioner with the current pharmacological treatment for dealing with perioperative pulmonary hypertensive crisis in PAH-CHD patients. Given the life-threatening complications associated with pulmonary hypertensive crisis, proper perioperative planning can help anticipate cardiopulmonary complications and optimize surgical outcomes in this patient population.

Reducing variation in the use of inhaled nitric oxide

BACKGROUND AND OBJECTIVE

Decreasing practice variation and following clinical guidelines improve patient outcomes and reduce costs. Inhaled nitric oxide (iNO) is an effective but expensive treatment of pulmonary hypertension and right heart failure in patients with congenital or acquired heart disease. Our objective was to implement standardized initiation and weaning guidelines for iNO usage in the cardiothoracic ICU (CTICU) to reduce variation in use while maintaining quality patient care.

METHODS

All CTICU patients who received iNO from January 2011 to December 2012 were retrospectively reviewed. Standardized iNO initiation and weaning guidelines were implemented in January 2012. Variables before and after guideline implementation were compared.

RESULTS

From January to December 2011, there were 36 separate iNO events (6% of CTICU admissions; n = 547). Mean ± SD iNO usage per event was 159 ± 177 hours (median: 63 hours; range: 27-661 hours). From January to December 2012, there were 47 separate iNO events (8% of CTICU admissions; n = 554). Mean iNO usage per event was 125 ± 134 hours (median: 72 hours; range: 2-557 hours). Initiation guideline compliance improved from 83% to 86% (P = .9); weaning guideline compliance improved from 17% to 79% (P < .001). Although mean iNO usage per event decreased, there was no significant reduction in utilization of iNO (P = .09).

CONCLUSIONS

Implementation of standardized iNO initiation and weaning guidelines in the CTICU was successful in reducing practice variation supported by increasing guideline compliance. However, decreasing practice variation did not significantly reduce iNO utilization and does not necessarily reduce cost.

Nitric oxide deficiency in pulmonary hypertension: Pathobiology and implications for therapy

Nitric oxide (NO) is a diffusible gas with diverse roles in human physiology and disease. Significant progress in the understanding of its biological effects has taken place in recent years. This has led to a better understanding of the pathobiology of pulmonary hypertension (PH) and the development of new therapies. This article provides an overview of the NO physiology and its role in the pathobiology of lung diseases, particularly PH. We also discuss current and emerging specific treatments that target NO signaling pathways in PH.

Right ventricular pulmonary hypertension

In heart failure (HF) syndrome, the development of pulmonary hypertension (PH), right ventricular (RV) dysfunction and failure are ominous prognostic signs. Pathophysiology, clinical interest and targeted therapeutic approaches for left-sided PH and its consequences on RV function have been traditionally confined to advanced HF stages. Community- and population-based studies have clearly indicated that PH is frequent even in HF patients with preserved ejection fraction, and may carry important prognostic implications in normal ageing as well. HF guidelines are inconclusive on both preventive and curative strategies for left-sided PH and its consequences on RV function. The search for new therapeutic opportunities targeted on pulmonary vascular and right heart remodeling are an important challenge for the future.

Intrapulmonary shear stress enhancement: a new therapeutic approach in pulmonary arterial hypertension

OBJECTIVE

Pulmonary arterial hypertension (PAH) is a dysfunctional endothelium disease with increased pulmonary vascular resistance (PVR) and poor prognosis. Current therapies are still insufficient. Here we propose a new pulsatile device as a more effective tool for PAH management compared with traditional treatments.

MATERIALS AND METHODS

Twelve piglets (10.3 ± 3.8 kg) were given either intrapulmonary pulsatile [P (n = 6)] or nonpulsatile [NP (n = 6)] tadalafil treatment. After median sternotomy and heparin injection (250 IU/kg), both groups underwent aorto-pulmonary surgical shunt for 1 h. During a second 1 h period in group P, a catheter prototype, driven by a small ventilator, was introduced into the pulmonary trunk and pulsated intermittently at 110 bpm irrespective of heart rate (90.6 ± 10.74 bpm). In group NP, tadalafil was given orally (1 mg/kg).

RESULTS

Hemodynamics and cardiac output (CO) were significantly (p < 0.05) improved in group P compared with group NP: CO was 0.56 ± 0.0.26 versus 0.54 ± 0.11 (L/min), respectively. Mean pulmonary artery pressure (PAP) was decreased in group P compared with group NP: PAP was 9.6 ± 2.97 versus 32.2 ± 5.07, respectively. Vascular resistances (dynes.s.cm(-5)/kg) were significantly lower in group P versus group NP: pulmonary resistance was 85 ± 42.12 versus 478 ± 192.91 and systemic resistance was 298.8 ± 172.85 versus 1301 ± 615.79, respectively. Using Western blot analysis, endogenous NO synthase expression in PA segments was nonsignificantly (p > 0.05) greater in group P (0.81 ± 0.78) versus (0.62 ± 0.35) group NP.

CONCLUSION

Induced with an appropriate device, intrapulmonary shear stress-mediated endothelial function enhancement provides a more effective nearly physiological therapy for PAH.

Treatment for pulmonary hypertension of left heart disease

OPINION STATEMENT

Pulmonary hypertension (PH) secondary to left heart disease is a largely underestimated target of therapy. Except for a specific focus on PH consequences in patients with advanced heart failure (HF) receiving a left ventricular mechanical assist device or candidates for transplantation, prevention and treatment of initial subclinical forms of PH are not considered a priority in the management of this chronic disease population. Nonetheless, there is recent growing evidence supporting a clinical and prognostic role of PH in the elderly and in HF with preserved ejection fraction (pEF). Studies have defined PH-HFpEF as a new entity typically defining the evolving nature of disease. Although the prevalence of PH in these populations is not well-defined, the potential for effective pharmacological approaches that might impact the natural history of the disease starting from earlier stages is promising. However, it should be recognized that pharmacological studies performed to date with traditional pulmonary vasodilators in cohorts with HF and left-sided PH have not been positive, primarily because of concomitant systemic hypotension and hepatic side effects. This evidence along with the lack of studies specifically performed in the elderly and HFpEF often lead Guidelines to give neutral recommendations or even arbitrary assumptions. Recent availability of selective well-tolerated pulmonary vasodilators, such as phosphodiesterase type 5 (PDE5) inhibitors, however, seem to offer a solid background for treating left-sided PH at both early and later stages of the disease process.

Clinical perspectives with long-term pulsed inhaled nitric oxide for the treatment of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a chronic, progressive disease of the pulmonary vasculature with a high morbidity and mortality. Its pathobiology involves at least three interacting pathways – prostacyclin (PGI₂), endothelin, and nitric oxide (NO). Current treatments target these three pathways utilizing PGI₂ and its analogs, endothelin receptor antagonists, and phosphodiesterase type-5 (PDE-5) inhibitors. Inhaled nitric oxide (iNO) is approved for the treatment of hypoxic respiratory failure associated with pulmonary hypertension in term/near-term neonates. As a selective pulmonary vasodilator, iNO can acutely decrease pulmonary artery pressure and pulmonary vascular resistance without affecting cardiac index or systemic vascular resistance. In addition to delivery via the endotracheal tube, iNO can also be administered as continuous inhalation via a facemask or a pulsed nasal delivery. Consistent with a deficiency in endogenously produced NO, long-term pulsed iNO dosing appears to favorably affect hemodynamics in PAH patients, observations that appear to correlate with benefit in uncontrolled settings. Clinical studies and case reports involving patients receiving long-term continuous pulsed iNO have shown minimal risk in terms of adverse events, changes in methemoglobin levels, and detectable exhaled or ambient NO or NO₂. Advances in gas delivery technology and strategies to optimize iNO dosing may enable broad-scale application to long-term treatment of chronic diseases such as PAH.

Reactive oxygen and nitrogen species in pulmonary hypertension

Pulmonary vascular disease can be defined as either a disease affecting the pulmonary capillaries and pulmonary arterioles, termed pulmonary arterial hypertension, or a disease affecting the left ventricle, called pulmonary venous hypertension. Pulmonary arterial hypertension (PAH) is a disorder of the pulmonary circulation characterized by endothelial dysfunction, as well as intimal and smooth muscle proliferation. Progressive increases in pulmonary vascular resistance and pressure impair the performance of the right ventricle, resulting in declining cardiac output, reduced exercise capacity, right-heart failure, and ultimately death. While the primary and heritable forms of the disease are thought to affect over 5000 patients in the United States, the disease can occur secondary to congenital heart disease, most advanced lung diseases, and many systemic diseases. Multiple studies implicate oxidative stress in the development of PAH. Further, this oxidative stress has been shown to be associated with alterations in reactive oxygen species (ROS), reactive nitrogen species (RNS), and nitric oxide (NO) signaling pathways, whereby bioavailable NO is decreased and ROS and RNS production are increased. Many canonical ROS and NO signaling pathways are simultaneously disrupted in PAH, with increased expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases and xanthine oxidoreductase, uncoupling of endothelial NO synthase (eNOS), and reduction in mitochondrial number, as well as impaired mitochondrial function. Upstream dysregulation of ROS/NO redox homeostasis impairs vascular tone and contributes to the pathological activation of antiapoptotic and mitogenic pathways, leading to cell proliferation and obliteration of the vasculature. This paper will review the available data regarding the role of oxidative and nitrosative stress and endothelial dysfunction in the pathophysiology of pulmonary hypertension, and provide a description of targeted therapies for this disease.

Review of inhaled nitric oxide in the pediatric cardiac surgery setting

Surgical intervention for congenital heart disease (CHD) can be complicated by pulmonary hypertension (PH), which increases morbidity, mortality, and medical burden. Consequently, postoperative management of PH is an important clinical consideration to improve outcomes. Inhaled nitric oxide (iNO) is a widely accepted standard of care for PH and has been studied in the context of cardiac surgery for CHD. However, large randomized, double-blind, placebo-controlled, multicenter clinical trials in pediatric patients are limited. This review will provide an overview of the clinical studies in this setting and will discuss general treatment considerations to facilitate a better understanding of the clinical use of iNO for PH after pediatric cardiac surgery.

Comparison of acute hemodynamic effects of aerosolized iloprost and inhaled nitric oxide in adult congenital heart disease with severe pulmonary arterial hypertension

OBJECTIVE

To compare the acute hemodynamic effects of aerosolized iloprost and inhaled nitric oxide (NO) in adult congenital heart disease (CHD) patients with severe pulmonary arterial hypertension (PAH).

METHODS

One hundred and eighty five adult CHDs with severe PAH were nonrandomized into two groups (iloprost, n=127; NO, n=58). Various hemodynamic parameters were measured before and after iloprost or NO inhalation.

RESULTS

Iloprost and NO inhalation resulted in significant reductions in pulmonary arterial pressure (from 110.6±21.8 mmHg to 105.5±22.3 mmHg, p<0.05; from 113.1±18.7 mmHg to 107.2±19.9 mmHg, p<0.05, respectively) and pulmonary vascular resistance (PVR) (from 13.4±8.3 Wood units to 9.6±6.4 Wood units, p<0.01; from 13.7±7.1 Wood units to 9.3±4.9 Wood units, p<0.01, respectively) and increases in pulmonary blood flow (from 6.7±3.3 L/min to 9.4±5.8 L/min, p<0.05; from 6.6±3.1 L/min to 9.6±5.9 L/min, p<0.01, respectively) and the Qp/Qs ratio (from 1.5±0.8 to 2.1±1.4, p<0.01; from 1.5±0.8 to 2.0±1.3, p<0.01, respectively). When the effects of inhaled iloprost and NO were compared, similar reductions in pulmonary arterial pressure and pulmonary vascular resistance were observed. Aerosolized iloprost and inhaled nitric oxide (iNO) were generally well tolerated and no patient experienced any side effects during inhalation.

CONCLUSION

Aerosolized iloprost can be effectively and safely used and might be an alternative to NO for testing pulmonary vascular reactivity and treating severe PAH in adult CHD patients.

Inhaled nitric oxide and inhaled prostacyclin in acute respiratory distress syndrome: what is the evidence?

The mortality for acute respiratory distress syndrome remains unacceptably high. Two vasodilators, inhaled prostacyclin and inhaled nitric oxide, are reviewed in this article. Knowledge of inhaled prostacyclin has grown substantially in the past 30 years, but less research exists about its utility in acute respiratory distress syndrome. Inhaled prostacyclin and other prostaglandin derivatives are used in acute respiratory distress syndrome with increasing frequency. Currently, only randomized controlled trials exist for inhaled nitric oxide in acute respiratory distress syndrome patients. Randomized controlled trials with consistent dosing methods are needed for both vasodilators to better define their role in the treatment of acute respiratory distress syndrome.

Sildenafil therapy for neonatal and childhood pulmonary hypertensive vascular disease

OBJECTIVES

We hypothesised that sildenafil would improve hemodynamics in children with pulmonary hypertension and attenuate rebound pulmonary hypertension after inhaled nitric oxide withdrawal.

PATIENTS AND METHODS

We undertook an open-label, single-drug study of sildenafil in patients under 5 years of age with either symptomatic or rebound pulmonary hypertension following inhaled nitric oxide withdrawal.

RESULTS

We recruited 25 patients (median age 180 days, 10-1790) to receive sildenafil. The median right ventricular to systemic systolic blood pressure ratio before sildenafil therapy was 1.0 (0.5-1.4) and decreased to 0.5 (with a range from 0.3 to 1.3; p = 0.0002). In five patients the baseline pulmonary vascular resistance index was 10 (7.1-13.6) Wood units metre square and decreased to 5.8 (2.7-15.6) Wood units metre square (p = 0.04) at 6 months. Ten patients were treated with sildenafil for a median of 34 days (9-499) until resolution of pulmonary artery hypertension and continue to do well. Six patients continued sildenafil therapy for a median of 1002 days (384-1574) with improvement but without resolution of pulmonary hypertension. There was no change in serum creatinine, urea, liver function tests, or platelet count. In 15 patients sildenafil abolished rebound pulmonary artery hypertension following withdrawal of inhaled nitric oxide. Median right ventricular pressure to systemic systolic pressure ratio decreased from 1.0 (0.8-1.4) during nitric oxide withdrawal to 0.4 (0.3-0.8) p = 0.006 after pre-treatment with sildenafil.

CONCLUSION

In children under 5 years of age with severe pulmonary hypertension, sildenafil therapy resulted in prolonged hemodynamic improvements without adverse effects. Sildenafil attenuated rebound pulmonary hypertension after withdrawal of inhaled nitric oxide.

Pulmonary hypertension with left-sided heart disease

Pulmonary hypertension (PH) with left-sided heart disease is defined, according to the latest Venice classification, as a Group 2 PH, which includes left-sided ventricular or atrial disease, and left-sided valvular diseases. These conditions are all associated with increased left ventricular filling pressure. Although PH with left-sided heart disease is a common entity, and long-term follow-up trials have provided firm recognition that development of left-sided PH carries a poor outcome, available data on incidence, pathophysiology, and therapy are sparse. Mitral stenosis was reported as the most frequent cause of PH several decades ago, but PH with left-sided heart disease is now usually caused by systemic hypertension and ischemic heart disease. In patients with these conditions, PH develops as a consequence of impaired left ventricular relaxation and distensibility. Chronic sustained elevation of cardiogenic blood pressure in pulmonary capillaries leads to a cascade of untoward retrograde anatomical and functional effects that represent specific targets for therapeutic intervention. The pathophysiological and clinical importance of the hemodynamic consequences of left-sided heart disease, starting with lung capillary injury and leading to right ventricular overload and failure, are discussed in this Review, focusing on PH as an evolving contributor to heart failure that may be amenable to novel interventions.

Pulmonary hypertension in heart failure

BACKGROUND

Pulmonary hypertension occurs in 60% to 80% of patients with heart failure and is associated with high morbidity and mortality.

METHODS AND RESULTS

Pulmonary artery pressure correlates with increased left ventricular end-diastolic pressure. Therefore, pulmonary hypertension is a common feature of heart failure with preserved as well as reduced systolic function. Pulmonary hypertension is partially reversible with normalization of cardiac filling pressures. Pulmonary vasculature remodeling and vasoconstriction create a second component, which does not reverse immediately, but has been shown to improve with vasoactive drugs and especially with left ventricular assist devices.

CONCLUSION

Many drugs used for idiopathic pulmonary arterial hypertension are being considered as treatment options for heart failure-related pulmonary hypertension. This is of particular significance in the heart transplant population. Randomized clinical trials with interventions targeting heart failure patients with elevated pulmonary artery pressure would be justified.

Anesthetic considerations for patients with advanced valvular heart disease undergoing noncardiac surgery

Patients with valvular heart disease represent a growing segment of the population and can present major challenges to clinical anesthesiologists. This review focuses on patients with advanced left-sided valvular disease undergoing noncardiac surgery. The pathophysiology and anesthetic implications of aortic stenosis and insufficiency and mitral stenosis and insufficiency are discussed, with a focus on optimizing perioperative management and decision making for patients with these conditions.

GTP cyclohydrolase I expression is regulated by nitric oxide: role of cyclic AMP

Our previous studies have demonstrated that nitric oxide (NO) leads to nitric oxide synthase (NOS) uncoupling and an increase in NOS-derived superoxide. However, the cause of this uncoupling has not been adequately resolved. The pteridine cofactor tetrahydrobiopterin (BH(4)) is a critical determinant of endothelial NOS (eNOS) activity and coupling, and GTP cyclohydrolase I (GCH1) is the rate-limiting enzyme in its generation. Thus the initial purpose of this study was to determine whether decreases in BH(4) could underlie, at least in part, the NO-mediated uncoupling of eNOS we have observed both in vitro and in vivo. Initially we evaluated the effect of inhaled NO levels on GCH1 expression and BH(4) levels in the intact lamb. Contrary to our hypothesis, we found that there was a significant increase in both plasma BH4 levels and peripheral lung GCH1 protein levels. Furthermore, in vitro, we found that exposure to the NO donor spermine NONOate (SPNONO) led to an increase in GCH1 protein and BH(4) levels in both COS-7 and pulmonary arterial endothelial cells. However, SPNONO treatment also caused a significant increase in phospho-cAMP response element binding protein (CREB) levels, as detected by Western blot analysis, and significantly increased cAMP levels, as detected by enzyme immunoassay. Furthermore, utilizing GCH1 promoter fragments fused to a luciferase reporter gene, we found that GCH1 promoter activity was enhanced by SPNONO in a CREB-dependent manner, and electromobility shift assays revealed an NO-dependent increase in the nuclear binding of CREB. These data suggest that NO increases BH(4) levels through a cAMP/CREB-mediated increase in GCH1 transcription and that the eNOS uncoupling associated with exogenous NO does not involved reduced BH(4) levels.

Effects of inhaled aerosolized iloprost and inhaled NO on pulmonary circulation and edema formation in ovine lung injury

Although inhaled NO (iNO) has been shown to lower pulmonary pressures and edema accumulation in experimental acute lung injury, its clinical use has been questioned because of a lack of improvement in outcome, rebound phenomena, and potential toxicity. We investigated the effects of aerosolized iloprost, a stable prostacyclin analogue, compared with iNO on pulmonary pressures and lung edema in 20 female sheep with oleic acid lung injury. The most effective dose of iloprost was determined in healthy animals before the experiment. Anesthetized and ventilated sheep received a central venous oleic acid infusion and were continuously infused with Ringer lactate to achieve a positive fluid balance (5 mL.kg(-1).h(-1)). In the iNO group (n = 6), iNO (20 ppm) was administered continuously for 8 h. Animals in the iloprost group (n = 6) received aerosolized iloprost (40 microg 2 h(-1)). Animals in the control group (n = 6) had no further intervention. Oleic acid infusion was associated with impaired oxygenation, pulmonary hypertension, and lung edema in all groups. Although iNO significantly decreased pulmonary vascular resistance index, effective pulmonary capillary pressure, and extravascular lung water index, these parameters were unaffected by iloprost. Oxygenation index (Pao2/Fio2) increased significantly both during NO and iloprost inhalation but also tended to improve in the control group over time. In contrast to iNO, the investigated dose of iloprost was ineffective to attenuate acute lung injury-induced changes in pulmonary hemodynamics and lung edema in this experimental model.

[Severe pulmonary hypertension: implications for anesthesia in laparoscopic surgery]

Pulmonary arterial hypertension (PAH), defined by a mean pulmonary arterial pressure greater than 25 mm Hg at rest or greater than 30 mm Hg with exercise, poses a challenge to anesthesiologists during perioperative management. The pathogenesis of PAH is multifactorial and includes genetic factors that explain individual susceptibility and external trigger or risk factors. We report the case of a woman with severe pulmonary hypertension who was waiting for a lung transplant when she was scheduled for laparoscopic cholecystectomy. We discuss the clinical course and monitoring of hemodynamic and respiratory parameters at the different stages of laparoscopic surgery.

The nitric oxide/cGMP signaling pathway in pulmonary hypertension

This article briefly reviews the background of endothelium-dependent vasorelaxation, describes the nitric oxide/cGMP/protein kinase pathway and its role in modulating pulmonary vascular tone and remodeling, and describes three approaches that target the nitric oxide/cGMP pathway in the treatment of patients with pulmonary arterial hypertension.