The endothelin antagonist BQ123 reduces pulmonary vascular resistance after surgical intervention for congenital heart disease

A systematic review of the evidence supporting post-operative medication use in congenital heart disease

BACKGROUND

Targeted drug development efforts in patients with CHD are needed to standardise care, improve outcomes, and limit adverse events in the post-operative period. To identify major gaps in knowledge that can be addressed by drug development efforts and provide a rationale for current clinical practice, this review evaluates the evidence behind the most common medication classes used in the post-operative care of children with CHD undergoing cardiac surgery with cardiopulmonary bypass.

METHODS

We systematically searched PubMed and EMBASE from 2000 to 2019 using a controlled vocabulary and keywords related to diuretics, vasoactives, sedatives, analgesics, pulmonary vasodilators, coagulation system medications, antiarrhythmics, steroids, and other endocrine drugs. We included studies of drugs given post-operatively to children with CHD undergoing repair or palliation with cardiopulmonary bypass.

RESULTS

We identified a total of 127 studies with 51,573 total children across medication classes. Most studies were retrospective cohorts at single centres. There is significant age- and disease-related variability in drug disposition, efficacy, and safety.

CONCLUSION

In this study, we discovered major gaps in knowledge for each medication class and identified areas for future research. Advances in data collection through electronic health records, novel trial methods, and collaboration can aid drug development efforts in standardising care, improving outcomes, and limiting adverse events in the post-operative period.

Treatment With Endothelin-A Receptor Antagonist BQ123 Attenuates Acute Inflammation in Mice Through T-Cell-Dependent Polymorphonuclear Myeloid-Derived Suppressor Cell Activation

The endothelin-A receptor antagonist BQ123 is an effective treatment agent for hypertension and obese cardiomyopathy. However, the role of BQ123 in controlling acute inflammatory diseases and its underlying mechanisms are not well understood. Here, we showed that BQ123 activated polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) in mice and that the IL13/STAT6/Arg1 signaling pathway is involved in this process. Importantly, both treatment with BQ123 and the transfer of BQ123-induced PMN-MDSCs (BQ123-MDSCs) were effective in relieving inflammation, including dextran sulfate sodium (DSS)-induced colitis, papain-induced pneumonia, and concanavalin A (ConA)-induced hepatitis, in mice. The treatment effects were mediated by the attenuation of the inflammation associated with the accumulation of PMN-MDSCs in the colon, lung, and liver. However, concurrent injection of Gr1 agonistic antibody with BQ123 induced PMN-MDSC aggravated the observed acute inflammation. Interestingly, no remission of inflammation was observed in Rag2 knockout mice administered BQ123-MDSCs, but co-injection with CD3⁺ T cells significantly relieved acute inflammation. In summary, BQ123-induced PMN-MDSCs attenuated acute inflammation in a T cell-dependent manner, providing a novel potential strategy to prevent the occurrence of acute inflammation.

Pulmonary Hypertension

OBJECTIVES

To review the clinical classification, diagnosis, and pathophysiology of pulmonary hypertension in children, emphasizing the role of right ventricular function, ventricular interaction, and congenital heart disease in the evolution and progression of disease, as well as management strategies and therapeutic options.

DATA SOURCE

MEDLINE, PubMed.

CONCLUSIONS

Critically ill children with pulmonary hypertension associated with congenital heart disease are a high-risk population. Congenital cardiac defects resulting in either increased pulmonary blood flow or impaired pulmonary venous drainage predispose patients to developing structural and functional aberrations of the pulmonary vasculature. Mortality from pulmonary hypertension is most directly related to right ventricular failure.

Cardiopulmonary bypass is associated with altered vascular reactivity of isolated pulmonary artery in a porcine model: therapeutic potential of inhaled tezosentan

OBJECTIVE

Whereas it is established that endothelin-1 elicits sustained deleterious effects on the cardiovascular system during cardiopulmonary bypass (CPB), presently it remains unknown whether the inhaled administration of the dual ETA and ETB antagonist tezosentan prevents the development of pulmonary endothelial dysfunction.

DESIGN

A prospective, randomized laboratory investigation.

SETTING

University research laboratory.

PARTICIPANTS

Landrace swine.

INTERVENTIONS

Three groups of animals underwent a 90-minute period of full bypass followed by a 60-minute period of reperfusion. Among treated groups, one received tezosentan through inhalation prior to CPB, whereas the other one received it intravenously at weaning from CPB; the third group remained untreated. Pulmonary vascular reactivity studies, realized on a total of 285 rings, were performed in all groups, including 1 sham.

MEASUREMENTS AND MAIN RESULTS

The contractility of pulmonary arteries to prostaglandin F2α and to the thromboxane A2 mimetic U46619 was preserved in animals submitted to CPB. By contrast, there were significant increases both in the maximal contraction to endothelin-1 and in the plasma levels of the peptide 60 minutes after reperfusion. Tezosentan administered by inhalation or intravenously did not prevent the development of pulmonary CPB-associated endothelial dysfunction. However, while hemodynamic disturbances were improved with both routes, the inhaled administration had a beneficial effect on oxygen parameters over intravenous administration.

CONCLUSIONS

Despite the blockade of the endothelin-1 pathway with tezosentan, the development of the pulmonary endothelial dysfunction associated with CPB still occurred. However, only the inhalation route had a significant impact on gas exchange during CPB.

Accurate measurement of oxygen consumption in children undergoing cardiac catheterization

Oxygen consumption (VO(2) ) is an important part of hemodynamics using the direct Fick principle in children undergoing cardiac catheterization. Accurate measurement of VO(2) is vital. Obviously, any error in the measurement of VO(2) will translate directly into an equivalent percentage under- or overestimation of blood flows and vascular resistances. It remains common practice to estimate VO(2) values from published predictive equations. Among these, the LaFarge equation is the most commonly used equation and gives the closest estimation with the least bias and limits of agreement. However, considerable errors are introduced by the LaFarge equation, particularly in children younger than 3 years of age. Respiratory mass spectrometry remains the "state-of-the-art" method, allowing highly sensitive, rapid and simultaneous measurement of multiple gas fractions. The AMIS 2000 quadrupole respiratory mass spectrometer system has been adapted to measure VO(2) in children under mechanical ventilation with pediatric ventilators during cardiac catheterization. The small sampling rate, fast response time and long tubes make the equipment a unique and powerful tool for bedside continuous measurement of VO(2) in cardiac catheterization for both clinical and research purposes.

Pharmacotherapy for pulmonary hypertension

Pulmonary arterial hypertension is a serious disease with significant morbidity and mortality. Although it can occur idiopathically, it is more commonly associated with other cardiac or lung diseases. While most of the available therapies have been tested in adult populations and most therapies in children remain off-label, new reports and randomized trials are emerging that inform the treatment of pediatric populations. This review discusses currently available therapies for pediatric pulmonary hypertension, their biological rationales, and evidence for their clinical effectiveness.

Systemic oxygen transport derived by using continuous measured oxygen consumption after the Norwood procedure-an interim review

The balance between systemic O(2)consumption (VO(2)) and O(2)delivery (DO(2)) is impaired in children after cardiopulmonary bypass surgery, with decreased DO(2)and increased VO(2). The major goal, and the major challenge, of postoperative management has been to match DO(2)to VO(2)in order to sustain cellular metabolism, particularly in neonates after the Norwood procedure. While much effort has been put into augmenting cardiac output and DO(2), VO(2)remains largely ignored. Respiratory mass spectrometry allows the precise and continuous measurement of VO(2). Measured VO(2), using the direct Fick principle, allows for the calculation of each element of systemic O(2)transport in the complex Norwood circulation. The actual measurements of O(2)transport have allowed us, in the past five years or so, to extensively investigate the Norwood physiology in terms of the VO(2)-DO(2)relationship and the factors affecting it in clinical treatments. Therefore, the first objective of this article is to introduce the technique of respiratory mass spectrometry and its adaption to measure VO(2)across paediatric ventilators with continuous flow. The second objective is to give an interim review of the main findings in our studies on systemic O(2)transport in 17 neonates in the first 72 h after the Norwood procedure. These findings include the profiles of systemic O(2)transport, the important contribution of VO(2)to the impaired balance of O(2)transport and the complex effects of some routine clinical treatments on the VO(2)-DO(2)relationship (including catecholamines, PaCO(2), Mg(2+)and hyperglycaemia, as well as patient-specific anatomical variations). The influence of systemic O(2)transport on cerebral oxygenation is also introduced. This information may help us to refine postoperative management in neonates after the Norwood procedure. Our initial studies mark the end of the beginning, but much is yet explored. Ultimately, the resultant improved systemic and regional O(2)transport in the early postoperative period may have an important impact on long-term outcomes, thereby improving the quality of life for these vulnerable children.

Pediatric pulmonary arterial hypertension: current and emerging therapeutic options

INTRODUCTION

Pulmonary arterial hypertension (PAH) is a rare disease in neonates, infants and children that is associated with significant morbidity and mortality. An adequate understanding of the controlling pathophysiologic mechanisms is lacking and although mortality has decreased as therapeutic options have increased over the past several decades, outcomes remain unacceptable.

AREAS COVERED

This review summarizes the currently available therapies for neonates, infants and children with PAH and describes emerging therapies in the context of what is known about the underlying pathophysiology of the disease.

EXPERT OPINION

All of the currently approved PAH therapies impact one of three endothelial-based pathways: nitric oxide-guanosine-3'-5'cyclic monophosphate, prostacyclin or endothelin-1. The beneficial effects of these agents may relate to their impact on pulmonary vascular tone, and/or their antiproliferative and antithrombotic properties. Fundamental advances in PAH therapy are likely to relate to: i) a better understanding of PAH subpopulations, allowing for therapies to be better tailored to individual patients and pathophysiologic processes; and ii) therapies that promote the regression of advanced structural remodeling.

Pathophysiology of acute pulmonary vasoconstriction

Acute pulmonary vasoconstriction occurs in a variety of clinical settings relevant for the cardiac intensivist, postoperative pulmonary hypertension being perhaps the most common. Although we know that significant postoperative pulmonary vasoconstriction generally occurs in patients with a pathologically remodeled pulmonary circulation, we know little of its pathophysiology. The following review describes the biochemistry of smooth muscle contractile activation and examines the possible role that endothelin-1 may play in postoperative pulmonary hypertension.

The role of calcium channel blockers, steroids, anticoagulation, antiplatelet drugs, and endothelin receptor antagonists

The rationale for the drug therapy of pulmonary artery hypertension is to reduce mortality and morbidity caused by failure of right ventricular adaptation to an elevated pulmonary vascular resistance. We review the evidence for the use of calcium-channel blockers, steroids, anticoagulation, antiplatelet drugs, and endothelin receptor antagonists in the management of pulmonary artery hypertension. The drugs we discuss are more suited to long-term outpatient therapy. These drugs have not found a routine place in intensive care management, and calcium-channel blockers are contraindicated in patients with right-heart failure. The efficacy of many agents has been extrapolated from data acquired in adult patients and applied to children. All of us involved in the care of young patients with pulmonary artery hypertension should advocate for both the inclusion of younger patients in clinical trials and the design of distinctly pediatric trials with pharmaceutical and drug administration agencies. It is only with data derived from pediatric inclusive studies that we shall be able to recommend therapy with strong evidence. However, it is important to point out that the use of newer agents for the treatment of chronic pulmonary artery hypertension (prostacyclin, endothelin receptor antagonists, nitric oxide, and sildenafil) have not been shown to improve survival unequivocally and have relied on surrogates, such as exercise capacity. There are no long-term studies of survival benefit. Recent studies have included data on time to clinical worsening, which may be a more predictive surrogate of survival.

EDNRA variants associate with smooth muscle mRNA levels, cell proliferation rates, and cystic fibrosis pulmonary disease severity

Airway inflammation and pulmonary disease are heterogeneous phenotypes in cystic fibrosis (CF) patients, even among patients with the same cystic fibrosis transmembrane conductance regulator (CFTR) genotype. Endothelin, a proinflammatory peptide and smooth muscle agonist, is increased in CF airways, potentially contributing to the pulmonary phenotype. Four cohorts of CF patients were screened for variants in endothelin pathway genes to determine whether any of these variants associated with pulmonary function. An initial cohort of 808 CF patients homozygous for the common CF mutation, DeltaF508, showed significant association for polymorphisms in the endothelin receptor A gene, EDNRA (P = 0.04), but not in the related endothelin genes (EDN1, EDN2, EDN3, or EDNRB) or NOS1, NOS2A, or NOS3. Variants within EDNRA were examined in three additional cohorts of CF patients, 238 patients from Seattle, WA, 303 from Ireland and the U.K., and 228 from Cleveland, OH, for a total of 1,577 CF patients. The three additional groups each demonstrated a significant association between EDNRA 3'-untranslated region (UTR) variant rs5335 and pulmonary function (P = 0.002). At the molecular level, single nucleotide primer extension assays suggest that the effect of the variants is quantitative. EDNRA mRNA levels from cultured primary tracheal smooth muscle cells are greater for the allele that appears to be deleterious to lung function than for the protective allele, suggesting a mechanism by which increased receptor function is harmful to the CF airway. Finally, cell proliferation studies using human airway smooth muscle cells demonstrated that cells homozygous for the deleterious allele proliferate at a faster rate than those homozygous for the protective allele.

The effect of bosentan in patients with a failing Fontan circulation

OBJECTIVES

To investigate the effect of bosentan in patients with a failing Fontan circulation.

DESIGN

A multicentric open label, non-controlled study.

SETTING

5 tertiary care centres for congenital cardiology.

PATIENTS

We included 10 patients with a failing Fontan circulation. Their median age at inclusion was 12.12 years, with a range from 4.41 to 33,41 years. The median interval between the Fontan operation and inclusion was 7.84 years, with a range from 1.96 to 12,18 years. Participants received half the usual dose of bosentan for 4 weeks, and then the full dose for a further 12 weeks. MAIN MEASURES OF OUTCOMES: We assessed saturations of oxygen at rest and during exercise, using a 6 minutes walk test, at baseline, and during and after 16 weeks of treatment. At each visit, we assessed blood chemistry and hepatic function, and asked the patients to complete a questionnaire concerning quality of life. All medical events and possible side effects were recorded.

RESULTS

Of the cohort, 1 patient withdrew. The changes in saturations of oxygen, exercise performance, and scores for the questionnaire did not reach statistical significance for the whole group. We noted, nonetheless, that saturations of oxygen and/or exercise capacity improved in 5 of the patients. This was further confirmed when those patients deteriorated again when the drug was discontinued.

CONCLUSIONS

Our study failed to show significant improvement after 3 months of treatment with bosentan in a small group of patients with failing Fontan circulations. Some individuals, nonetheless, did improve. When planning larger trials, it would be better to identify those patients who might potentially benefit from the treatment prior to commencing the trial.

Inhaled iloprost to control pulmonary artery hypertension in patients undergoing mitral valve surgery: a prospective, randomized-controlled trial

BACKGROUND

Pulmonary hypertension (PHT) is common in patients undergoing mitral valve surgery and is an independent risk factor for the development of acute right ventricular (RV) failure. Inhaled iloprost was shown to improve RV function and decrease RV afterload in patients with primary PHT. However, no randomized-controlled trials on the intraoperative use of iloprost in cardiac surgical patients are available. We therefore compared the effects of inhaled iloprost vs. intravenous standard therapy in cardiac surgical patients with chronic PHT.

METHODS

Twenty patients with chronic PHT undergoing mitral valve repair were randomized to receive inhaled iloprost (25 microg) or intravenous nitroglycerine. Iloprost was administered during weaning from cardiopulmonary bypass (CPB). Systemic and pulmonary haemodynamics were assessed with pulmonary artery catheterization and transoesophageal echocardiography. Milrinone and/or inhaled nitric oxide were available as rescue medication in case of failure to wean from CPB.

RESULTS

Inhaled iloprost selectively decreased the pulmonary vascular resistance index after weaning from CPB (208 +/- 108 vs. 422 +/- 62 dyn.s/cm(5)/m(2), P<0.05), increased the RV-ejection fraction (29 +/- 3% vs. 22 +/- 5%, P<0.05), improved the stroke volume index (27 +/- 7 vs. 18 +/- 6 ml/m(2), P<0.05) and reduced the transpulmonary gradient (10 +/- 4 vs. 16 +/- 3 mmHg, P<0.05). In all patients receiving inhaled iloprost, weaning from CPB was successful during the first attempt. In contrast, three patients in the control group required re-institution of CPB and had to be weaned from CPB using rescue medication.

CONCLUSIONS

In patients with pre-existing PHT undergoing mitral valve surgery, inhaled iloprost is superior to intravenous nitrogylycerine by acting as a selective pulmonary vasodilator, reducing RV afterload and moderately improving RV-pump performance.

Congenital Heart Disease Associated Pulmonary Arterial Hypertension

Pulmonary arterial hypertension associated with congenital heart disease, although common (15%-30%) in all-comers with congenital heart disease, is variable in terms of clinical manifestations, severity of associated pulmonary arterial hypertension, and response to therapy and outcomes (depending on lesion anatomy, pulmonary circulation flows and pressures, and presence and timings of surgeries). Evaluation includes imaging and catheterization. Surgical or another anatomic correction may be desirable after rigorous preinterventional assessment. Patients who are not surgical candidates or who fail to improve early or late after surgery may have the potential to respond to idiopathic pulmonary arterial hypertension therapies. Lung or heart/lung transplantation remains an option for selected recalcitrant patients.

Pulmonary hypertension in children: the twenty-first century

Pulmonary hypertension is an elevation in pulmonary artery pressure that is associated with a spectrum of diseases and causes. Its clinical severity and presentation are widely varied. The field of study has changed immensely over the past several years. Significant knowledge has been gained in the pathophysiology, genetics, and vascular biology associated with pulmonary hypertension. These discoveries have contributed to medical interventions that have improved outcomes associated with pulmonary hypertension. This article reviews pulmonary hypertension in children, focusing on idiopathic pulmonary hypertension. Because most information is associated with children who have this form of the disease, formerly classified as primary pulmonary hypertension, medical therapy is discussed with a focus on this patient group. Additional therapeutic concepts relevant to other causes of pulmonary hypertension are highlighted.

Pulmonary perfusion during lipopolysaccharide (LPS) induced fetal endotoxemia in the preterm fetal sheep

OBJECTIVE

To study endotoxin induced changes in pulmonary blood flow during normoxia and hypoxia and analyzed the role of nitric oxide (NO) and endothelin (ET) in this process.

STUDY DESIGN

Twenty-seven fetal sheep were chronically instrumented at 107+/-1 days (term is 147 days). Experiments were performed 3 days after surgery. Fetuses were randomized into four groups. Group 1: control group (n=5); Group 2: LPS group (n=6) with lipopolysaccharide (LPS) injection at t -60min; Group 3: L-NAME (n=6) with nitro-l-arginine methyl ester (l-NAME) treatment at t -75min; Group 4: l-NAME+LPS group (n=6) with nitro-l-arginine methyl ester (l-NAME) pre-treatment at t -75min and LPS administration at t -60min as described above; Group 5: BQ123+LPS group (n=4) with BQ123 pre-treatment at t -75min and LPS injection at t -60min as described above.

RESULTS

Unlike in control fetuses, there was a marked elevation in pulmonary perfusion in response to LPS induced endotoxemia during normoxia (+112%; p<0.01), which was even further increased during hypoxia (+434%; p<0.001). This increase was partially blocked by BQ123 (p<0.05) and completely abolished by pre-treatment with l-NAME (p<0.001).

CONCLUSION

During fetal endotoxemia, pulmonary perfusion is increased by LPS induced production of nitric oxide. This may have a significant impact in the fetal inflammatory response syndrome, particularly in the inflammation of the fetal lungs observed in response to intrauterine infection.

Functional adaptation and remodeling of pulmonary artery in flow-induced pulmonary hypertension

Patients with left-to-right shunt congenital heart disease may develop pulmonary hypertension. Perioperative mortality of these patients is high due to abnormal vasoreactivity of the pulmonary artery (PA). We studied the changes in the PA induced by high pulmonary blood flow in rats with aortocaval fistula. Eight weeks after surgery, morphological changes of the PA were studied and vasomotor function was assessed by isometric force recording. Expression of endothelial nitric oxide (NO) synthase (eNOS), VEGF, and cyclooxygenase-2 (COX-2) proteins and levels of cGMP in the PA were analyzed. Rats with high pulmonary blood flow developed pulmonary hypertension, medial thickening, and increasing of internal elastic lamina and basement membrane in the PA. When compared with sham-operated animals, rats with fistula had significantly increased contractions in the PA, whereas relaxations to acetylcholine and NO donor were reduced. Concentrations of cGMP were reduced in the PA of rats with pulmonary hypertension (18.4 ± 3.3 vs. 9.4 ± 1.7 pmol/mg protein; P = 0.04). The altered vasomotor function was normalized by treatment with indomethacin. The PA of rats with fistula expressed higher levels of eNOS, phosphorylated eNOS, and COX-2. Sustained high PA blood flow in rats causes pulmonary hypertension that is morphologically and functionally identical with patients with flow-induced pulmonary hypertension. Abnormal vasomotor function of the PA in these animals appears to be mediated by reduced availability and the biological effect of endogenous NO and the high production of vasoconstrictor prostanoids. Increased eNOS and phosphorylated eNOS are most likely the adaptive changes in response to an increase in PA pressure secondary to high blood flow.

Endothelin-A receptor blockade prevents and partially reverses neonatal hypoxic pulmonary vascular remodeling

Hypoxia-induced pulmonary vascular remodeling (HPVR) may lead to persistent pulmonary hypertension of the newborn or cor pulmonale. Endothelin-1 (ET-1), via endothelin-A (ET(A)) receptor activation, mediates hypoxic pulmonary vasoconstriction. Our objectives were to develop a newborn mouse model of HPVR and to test the hypothesis that ET(A) blockade would prevent and reverse HPVR in this model. C57BL/6 mice (n = 64) were exposed to 12% oxygen (HYP group) or room air (RA group) from birth to 2 wk of age. The mice were injected intraperitoneally daily with either BQ-610 (ET(A) blocker) or vehicle (cottonseed oil) from birth (prevention study) or from 6 d of age (reversal study). HPVR was assessed histologically by pulmonary vascular morphometry by an examiner masked to study group, and by measurement of the right ventricle to left ventricle (RV/LV) thickness ratio. Hypoxia increased medial wall thickness (%WT) in pulmonary arteries <100 mum in diameter and RV/LV thickness ratio. BQ-610 prevented the hypoxia-induced increase in %WT and RV/LV thickness ratio when given from birth, and later therapy partially reversed the hypoxia-induced increase in %WT but not RV/LV thickness ratio. These data show that in the newborn mouse model, chronic hypoxia leads to HPVR that can be completely prevented and partially reversed by ET(A) blockade. These results indicate that ET-1, acting via ET(A) receptors, is a mechanism of pathophysiologic significance underlying neonatal HPVR. Development of this newborn mouse model of HPVR facilitates investigation of mechanisms underlying this important and severe disease entity in human infants.

Endothelin-1 in congenital heart disease

Endothelin-1 (ET-1) is a 21-amino acid polypeptide produced primarily by vascular endothelial cells. First discovered in 1988 as a potent vasoconstrictor, it has subsequently been appreciated to participate in several biologic activities, including vascular smooth muscle proliferation, fibrosis, cardiac and vascular hypertrophy, and inflammation. Increasing data demonstrate alterations in ET-1 signaling in newborns, infants, and children with congenital heart defects that are associated with alterations in pulmonary blood flow. This review outlines the pathophysiologic role of the ET-1 cascade in the development of altered pulmonary vascular tone and reactivity that occurs with congenital heart disease and its repair, following the use of cardiopulmonary bypass. In addition, therapeutic implications for the use of novel ET receptor antagonists will be emphasized.

Flap Valve Double Patch Closure of Ventricular Septal Defects in Children With Increased Pulmonary Vascular Resistance

BACKGROUND

Closure of a large ventricular septal defect (VSD) in children with elevated pulmonary vascular resistance (PVR) is associated with significant morbidity and mortality. Sophisticated medications and circulatory assist devices may not be available to assist in the care of children with elevated PVR undergoing VSD closure. We designed a fenestrated flap valve double VSD patch to decrease the morbidity and mortality associated with the closure of a large VSD in this high-risk group.

METHODS

Ninety-one children (median age 4.0 +/- 3.1 years) with a large VSD and elevated PVR (10.5 +/- 4.9 Wood units) underwent double patch VSD closure. The routine VSD patch was fenestrated (4 to 8 mm), and on the left ventricular side of the patch, a second smaller patch was attached to the upper third of the fenestration before VSD patch placement.

RESULTS

Fifty-six children with a VSD as the primary lesion, 16 with complete atrioventricular canal, 10 with double outlet right ventricle/VSD, 2 with interrupted aortic arch/VSD, 2 with truncus arteriosus, and 1 each with transposition/VSD, corrected transposition/VSD, total anomalous pulmonary venous connection/VSD, VSD/left pulmonary artery atresia, and aortopulmonary window underwent operation; the overall early mortality rate was 7.7% (7 of 91). There have been 7 late deaths: 2 VSD and 5 complex defects.

CONCLUSIONS

Closure of a large VSD with elevated PVR can be performed with reasonable mortality and morbidity.

Severe paediatric pulmonary hypertension: new management strategies

Pulmonary hypertension is a significant complication in many paediatric disease states. This article discusses current understanding of pulmonary hypertension and includes definition, diagnosis, and management. A description of the latest advances in targeted pharmacological therapy in children is also provided as well as impact on morbidity and mortality.

Endothelin-A receptor blockade and inhaled nitric oxide in a porcine model of meconium aspiration syndrome

Acute neonatal pulmonary hypertension is associated with increased activation of the endogenous endothelin pathway. We investigated the role of selective endothelin-A receptor blockade using i.v. BQ-123 in a piglet model of meconium aspiration syndrome. Meconium aspiration was induced in 18 anesthetized piglets. Six controls received no further intervention. Six piglets received 1 mg/kg BQ-123 at 120 min, with the addition of 20 ppm inhaled nitric oxide at 240 min. Six commenced nitric oxide therapy at 120 min, and were given i.v. BQ-123 at 240 min. The total study duration was 360 min. Meconium aspiration resulted in acute pulmonary hypertension and elevated endothelin-1 levels in all animals. There were no changes in pulmonary hemodynamics or endothelin-1 levels beyond 120 min in controls. In the group receiving BQ-123 first, this agent alone reduced the pulmonary artery pressure and pulmonary vascular resistance, and the subsequent addition of inhaled nitric oxide further reduced pulmonary artery pressure. In the group first receiving nitric oxide alone, this reduced the pulmonary artery pressure, and the addition of BQ-123 resulted in a fall in pulmonary vascular resistance. Endothelin-1 levels increased with both agents. BQ-123 was found to be a highly effective pulmonary vasodilator and augmented the effects of nitric oxide in this model of acute pulmonary hypertension.

Advances in postoperative care of pediatric cardiac patients

PURPOSE OF REVIEW

The past two decades have seen tremendous technological advances in the care of infants and children with congenital and acquired heart disease. Recent advances in postoperative management have made it possible to support smaller and more fragile infants, extended the capabilities of extracorporeal circulation, and have brought new and innovative monitoring capabilities to the intensive care unit.

RECENT FINDINGS

We chose to focus our review on four main themes: management of pulmonary hypertension, mechanical support of the myocardium, near infrared spectroscopy, and heparin-induced thrombocytopenia.

SUMMARY

As operative and cardiopulmonary bypass techniques have evolved, early complete repair in neonates and repair of more complex lesions is now possible, creating new challenges for postoperative care in the intensive care unit. Additionally, recognition and management of newly appreciated complications is essential.

Perioperative management in pediatric heart transplantation from 1988 to 2001: anesthetic experience in a single center

Pediatric cardiac transplantation is currently an accepted option for end-stage heart disease and congenital cardiac malformations. This report focuses on the anesthetic perioperative management in 12 yr. From 1988 to 2001 we performed 90 heart transplantations in 88 children, infants and neonates. The pediatric heart transplant program of the children's heart center at our university hospital started in June 1988 with the transplantation of a 2-yr-old boy who was suffering from congenital heart disease. Since then, 88 transplants have been performed. We divided our patients into two groups. Group 1 ranged from 1988 to 1996 and Group 2 from 1997 to 2001. The patient characteristics have not significantly changed over the years in our institution. At the time of transplantation, mean age of the patients was 2.6 +/- 4.3 yr from the period of 1988-1996 and 2.5 +/- 4.1 yr from 1997 to 2001. Since 1988, 90 transplants (Tx) in 88 patients have been performed. Two patients needed re-Tx within 2 days after the initial operation because of primary graft failure. Indications for Tx were congenital heart disease (n = 67) and cardiomyopathy (n = 21). In the subgroup of the patients suffering from congenital heart disease there were 46 with the diagnosis of HLHS, followed by endocardial fibroelastosis (n = 7); the remaining 14 patients had other complex cardiac malformations and some underwent corrective palliative cardiac surgery before Tx. Sixty-three patients were younger than 1 yr of age and only five children were older than 10 yr. Twenty-three percent of the patients on the waiting list died before Tx was possible. The overall survival rate was 79% at 1 yr and 73% at 5 and 10 yr. Infants with HLHS had a lower probability of survival after 5 yr compared with other diagnosis (69% vs. 84%). Until now 21 patients have died after Tx. The duration of anesthesia, time of CPB and the age at the time of surgery decreased over the years. It is always a challenge for the anesthesiologist to treat these patients with pulmonary hypertension as one of the most critical risks in this group of patients. The preventive therapy with vasodilators as well as the availability of mechanical assist devices before and after heart transplantation reduces the effects of transitional pulmonary hypertension and prevents the development of post-operative right heart failure.

Preoperative glucocorticoids decrease pulmonary hypertension in piglets after cardiopulmonary bypass and circulatory arrest

BACKGROUND

Glucocorticoids during cardiopulmonary bypass benefit pediatric patients undergoing repair of congenital heart defects and are routine therapy, but underlying mechanisms have not been fully examined. The hypothesis was that glucocorticoids could improve cardiopulmonary recovery after cardiopulmonary bypass and deep hypothermic circulatory arrest.

METHODS

Crossbred piglets (5 to 7 kg) were cooled with cardiopulmonary bypass, followed by 120-min deep hypothermic circulatory arrest. Animals were then warmed to 38 degrees C, removed from bypass, and maintained for 120 min. Methylprednisolone (60 mg/kg) was administered in the cardiopulmonary bypass pump prime (intraoperative glucocorticoids) or 6 hours before bypass (30 mg/kg) in addition to the intraoperative dose (30 mg/kg; preoperative and intraoperative glucocorticoids). Controls (no glucocorticoids) received saline.

RESULTS

Pulmonary vascular resistance in controls increased from a baseline of 152 +/- 40 to 364 +/- 29 dynes. s/cm(5) at 2 hours of recovery (p < 0.001). Intraoperative glucocorticoids did not alleviate the increase in pulmonary vascular resistance (301 +/- 55 dynes. s/cm(5) at 2 hours of recovery, p < 0.001). However, animals receiving pre and intraoperative glucocorticoids had no increase in pulmonary vascular resistance (155 +/- 54 dynes. s/cm(5)). Plasma endothelin-1 in controls increased from 1.3 +/- 0.2 at baseline to 9.9 +/- 2.0 pg/mL at 2 hours recovery (p < 0.01), whereas glucocorticoid-treated animals had lower endothelin-1 levels (4.5 +/- 2.1 pg/ml, preoperative and intraoperative glucocorticoids; 4.9 +/- 1.7 pg/mL, intraoperative glucocorticoids) at the end of recovery (p < 0.05). Intracellular adhesion molecule-1 in lung tissue was lower in animals receiving pre and intraoperative glucocorticoids (p < 0.05). Myeloperoxidase activity was elevated in control lungs at 2 hours of recovery compared with glucocorticoid-treated groups (p < 0.05). Inhibitor kappaBalpha, the inhibitor of nuclear factor-kappaB, was higher in lungs of animals receiving glucocorticoids compared with controls (p < 0.05).

CONCLUSIONS

Glucocorticoids prevented pulmonary hypertension after cardiopulmonary bypass and deep hypothermic circulatory arrest, which was associated with reduced plasma endothelin-1. Glucocorticoids also reduced pulmonary intercellular adhesion molecule-1 and myeloperoxidase activity. Inhibition of nuclear factor-kappaB, along with reduced neutrophil activation, contributed to glucocorticoid alleviation of pulmonary hypertension after cardiopulmonary bypass and deep hypothermic circulatory arrest.

The low resistance strategy for the perioperative management of the Norwood procedure

BACKGROUND

Postoperative course of the Norwood procedure is fragile because of an unstable pulmonary to systemic blood flow ratio caused by fluctuation of systemic and pulmonary vascular resistance.

METHODS

Twenty-seven patients with hypoplastic left heart syndrome who underwent the Norwood procedure from June 1998 to February 2002 were managed with the following low-resistance strategy. Intraoperative high-flow and low-resistance cardiopulmonary bypass was achieved with total avoidance of circulatory arrest and a large dose of chlorpromazine. In weaning from the bypass, pulmonary vascular resistance was maximally decreased by inspired oxygen fraction (100%), inhaled nitric oxide (20 ppm), and nitroglycerin (2 to 4 microg/kg/min). Then pulmonary blood flow was determined by adjusting the systemic to pulmonary shunt. Postoperatively, with continuous infusion of chlorpromazine and nitroglycerin as a systemic and pulmonary vasodilator, the inspired oxygen fraction and inhaled nitric oxide were tapered as the arterial oxygen saturation improved.

RESULTS

In most patients, inhaled nitrous oxide and inspired oxygen fraction were weaned within 3 days. The postoperative course was stable with minimum changes in circulatory and respiratory status for the survivors. Patients were extubated on a median of 6 postoperative days. Early mortality was 11.1% (3 of 27), and none of the patients died of hemodynamic deterioration.

CONCLUSIONS

The low resistance strategy is a simple and useful method for perioperative management of the Norwood procedure, minimizing fluctuation in both pulmonary and systemic vascular resistance and maintaining stable circulatory and respiratory status.