Effect of long term oxygen treatment at home in children with pulmonary vascular disease

Oxygen and pulmonary arterial hypertension: effects, mechanisms, and therapeutic benefits

Oxygen is a pulmonary vasodilator. Although treatment of pulmonary arterial hypertension (PAH) is focused on pulmonary vasodilation, treatment guidelines do not recommend O2 therapy for patients unless they develop hypoxaemia. These guidelines point to a lack of evidence of benefit of O2 therapy from randomized controlled trials (RCTs) and to evidence of lack of benefit in a single RCT involving patients with Eisenmenger syndrome. These guidelines did not identify major limitations with the Eisenmenger study or consider other evidence of therapeutic benefit. Recent advances in mechanistic understanding of O2 effects on pulmonary vascular tone, along with substantial evidence of acute effects of O2 in PAH patients, challenge the view that benefits of O2 arise only through correction of hypoxaemia. Evidence presented in this review shows that O2 acts as a pulmonary vasodilator in patients who are normoxaemic; that this probably involves an alveolar mechanism in addition to a blood-borne (oxyhaemoglobin) mechanism; and that therapeutic benefit of O2 does not depend on arterial O2 levels. This suggests that O2 has potential therapeutic benefit for all patients with PAH. Clinical guidelines and practice related to O2 therapy need to be reassessed, and further research is needed.

Home Oxygen Therapy for Children. An Official American Thoracic Society Clinical Practice Guideline

Background: Home oxygen therapy is often required in children with chronic respiratory conditions. This document provides an evidence-based clinical practice guideline on the implementation, monitoring, and discontinuation of home oxygen therapy for the pediatric population.

Methods: A multidisciplinary panel identified pertinent questions regarding home oxygen therapy in children, conducted systematic reviews of the relevant literature, and applied the Grading of Recommendations, Assessment, Development, and Evaluation approach to rate the quality of evidence and strength of clinical recommendations.

Results: After considering the panel’s confidence in the estimated effects, the balance of desirable (benefits) and undesirable (harms and burdens) consequences of treatment, patient values and preferences, cost, and feasibility, recommendations were developed for or against home oxygen therapy specific to pediatric lung and pulmonary vascular diseases.

Conclusions: Although home oxygen therapy is commonly required in the care of children, there is a striking lack of empirical evidence regarding implementation, monitoring, and discontinuation of supplemental oxygen therapy. The panel formulated and provided the rationale for clinical recommendations for home oxygen therapy based on scant empirical evidence, expert opinion, and clinical experience to aid clinicians in the management of these complex pediatric patients and identified important areas for future research.

Effects of oxygen therapy in a pediatric normoxemic patient with pulmonary arterial hypertension and congenital heart disease

To shed light on the efficacy of oxygen therapy in pulmonary arterial hypertension (PAH) when hypoxemia is not present, we report seven years of observational data for a female patient recorded between February 2012 and February 2019 when she was aged 7.8–14.8 years. The patient was born with an atrial septal defect (closed spontaneously at 2.3 years) and ventricular septal defect (surgically repaired at 8.3 years) and then diagnosed with PAH at 8.9 years . The patient was prescribed bosentan soon after diagnosis and for the next 4.8 years, during which a first phase of oxygen therapy (nocturnal) was trialed for 2.8 years. Mean pulmonary arterial pressure (mPAP) and systolic PAP (sPAP) remained stable and at mild levels when oxygen was administered, but then increased progressively to severe levels over two years without oxygen. This coincided with worsening right ventricular pathology during the later part of this period without oxygen. Re-initiation of more intensive oxygen therapy while the patient was still on bosentan and before pharmocotherapy was changed coincided with a large and rapid fall in sPAP, confirmed by right heart catheterization measurements of mPAP. During this entire observation period, the patient remained normoxemic. These observations challenge the notion that oxygen therapy should be restricted to patients with hypoxemia and strengthen calls for further study of oxygen therapy in PAH.

Insight into Pulmonary Arterial Hypertension Associated with Congenital Heart Disease (PAH-CHD): Classification and Pharmacological Management from a Pediatric Cardiological Point of View

Compared with adult patients with pulmonary hypertension (PH), pulmonary vascular disease is characterized by complex heterogeneity in pediatric patients. The Nice PH classification does not completely characterize or individualize any subgroup of pediatric PH. This is in contrast to the Panama classification, in which prenatal and fetal origins of many pulmonary vascular diseases in neonates and children, perinatal pulmonary vascular maladaptation, prenatal and postnatal pulmonary vascular mal-development, and pulmonary vascular hypoplasia are included. Currently, the updated treatment algorithm for adults with pulmonary arterial hypertension (PAH), including PAH associated with congenital heart disease (PAH-CHD) and idiopathic PAH, etc. has been reported. It has been suggested to treat FC III patients with Eisenmenger syndrome (ES) with bosentan. However, there is no evidence-based treatment algorithm for children with PAH-CHD. Moreover, it is necessary to develop a more comprehensive algorithm in which multiple specific pediatric risk factors are determined, and the critical goal of treatment should be to permit normal activities without the need to self-limit in children with PAH-CHD. Together, the beneficial data on specific-target pharmacologic interventions are still quite preliminary, and large trials are warranted. Specifically, the extrapolation of the other forms of the disease, such as ES, should be undertaken carefully.

KEY WORDS

Congenital heart disease; Eisenmenger syndrome; Pulmonary arterial hypertension; Target therapy.

Standard nonspecific therapies in the management of pulmonary arterial hypertension

Recent advances in pulmonary arterial hypertension (PAH) research have created a new era of PAH-specific therapies. Although these therapeutics have revolutionized PAH therapy, their innovation was predated by supportive but nonspecific medical therapies adapted from their use in more common cardiopulmonary diseases. These therapies include oxygen therapy, diuretics, digoxin, anticoagulation, and high-dose calcium channel blockers. Expert opinion continues to support the use of adjunct therapies based on current pathologic understandings of PAH combined with some evidence extrapolated from small studies. This article discusses why these therapies continue to play an important role in the treatment of patients with PAH.

Nocturnal hypoxaemia in patients with Eisenmenger syndrome: a cohort study

OBJECTIVES

The objective of the study was to find the prevalence of sleep-related disturbances in patients of Eisenmenger syndrome.

DESIGN

Prospective observational study.

SETTING

Tertiary care referral centre in North India.

PARTICIPANTS

The study included 25 patients with Eisenmenger syndrome (mean age 25.2±9.6 years, 18 men) and 12 patients with cyanotic congenital heart disease with pulmonary stenosis physiology (mean age 20.5±8.5 years, 8 men) as controls.

INTERVENTIONS

All the patients underwent an overnight comprehensive polysomnogram study and pulmonary function testing.

MAIN OUTCOME MEASURE

Oxygen desaturation index, which is the number of oxygen drops per hour.

RESULTS

The patients and controls had significant nocturnal hypoxaemia in the absence of apnoea and hypopnoea. The mean oxygen drop index in Eisenmenger syndrome group was 9.0±6.2 and in the control group was 8.0±5.9 (p=0.63). The apnoea-hypopnoea index was 3.37±5.0 in the Eisenmenger syndrome group and was 2.1±3.6 in the control group. Patients with >10 oxygen drops per hour had significantly higher haemoglobin (17.2±1.3% vs 14.4±1.5%, p<0.001) than those with oxygen drops less than 10.

CONCLUSIONS

Eisenmenger syndrome patients have significant nocturnal hypoxaemia unrelated to hypopnoea and apnoea. Nocturnal desaturation occurred more frequently in patients with greater haemoglobin values.

Recommendations for long-term home oxygen therapy in children and adolescents

OBJECTIVE

To advise pediatricians, neonatologists, pulmonologists, pediatric pulmonologists, and other professionals in the area on the main indications and characteristics of long-term home oxygen therapy in children and adolescents.

DATA SOURCE

A literature search was carried out in the MEDLINE/PubMed database (1990 to 2011). Additionally, references from selected studies were included. As consistent scientific evidence does not exist for many aspects, some of the recommendations were based on clinical experience.

DATA SYNTHESIS

Long-term home oxygen therapy has been a growing practice in pediatric patients and is indicated in bronchopulmonary dysplasia, cystic fibrosis, bronchiolitis obliterans, interstitial lung diseases, and pulmonary hypertension, among others. The benefits are: decrease in hospitalizations, optimization of physical growth and neurological development, improvement of exercise tolerance and quality of sleep, and prevention of pulmonary hypertension/cor pulmonale. The levels of oxygen saturation indicative for oxygen therapy differ from those established for adults with chronic obstructive pulmonary disease, and vary according to age and disease. Pulse oximetry is used to evaluate oxygen saturation; arterial blood gas is unnecessary. There are three available sources of oxygen: gas cylinders, liquid oxygen, and oxygen concentrators. The flows used are usually smaller, as are the number of hours/day needed when compared to the use in adults. Some diseases show improvement and oxygen therapy discontinuation is possible.

CONCLUSIONS

Long-term home oxygen therapy is increasingly common in pediatrics and has many indications. There are relevant particularities when compared to its use in adults, regarding indications, directions for use, and monitoring.

Management of pulmonary hypertension and Down syndrome

Down syndrome (DS) is strongly associated with pulmonary hypertension, but there are many causes requiring a multi-disciplinary approach to the problem. Nearly half of children with DS have upper airway obstruction and the same proportion have congenital heart disease, both of which may cause pulmonary hypertension. Additional problems include pulmonary hypoplasia, structural lung disease and gastro-oesophageal reflux. It is no longer acceptable to ignore these symptoms as early treatment may be preventative.

Management of pulmonary arterial hypertension in children

In this review we discuss the new anti- Pulmonary Arterial Hypertension [PAH] drugs and the available data on their use in paediatric PAH. Treatment of patients with PAH, children and adults, is aimed at a reduction of symptoms, survival and improvement of haemodynamics as well as exercise capacity. PAH may reflect significant different disease conditions in infants and children when compared to PAH in adults. In contrast to adult PAH, characterized mainly by idiopathic PAH and PAH associated with connective tissue disease, more than half of the cases of PAH in children are associated with congenital heart disease. Therefore, efficacy of PAH drugs in these diseases can not be extrapolated from that in adults with PAH.

Treatment options for paediatric pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a serious, progressive condition, which can present idiopathically or secondary to conditions such as systemic sclerosis or congenital heart disease. The condition exists in both adult and paediatric forms, which possess several similar characteristics. Adult and paediatric PAH can, however, be distinguished based on underlying pathology and the presence of age-specific conditions, some of which are related to poor lung development in children. Improved knowledge of vascular biology has led to the development of several PAH-specific therapies, which have demonstrated clinical benefits in adults, including improved exercise capacity and prolonged survival. Treatment data in paediatric PAH are scarce. Although limited, the existing data indicate that current treatments for paediatric PAH are well tolerated and effective, at least in the short- and medium-term. Nevertheless, the current guidelines for clinicians, which recommend use of the adult treatment algorithm in paediatric patients, appear justified when judged according to the available evidence. However, further randomised, controlled trials are necessary to increase the evidence base for treatment of paediatric PAH, especially in relation to age-specific conditions. At present, early initiation of treatment and combination pharmacological therapy may offer the most promising courses of action to improve outcomes in paediatric PAH.

Updated evidence-based treatment algorithm in pulmonary arterial hypertension

Uncontrolled and controlled clinical trials with different compounds and procedures are reviewed to define the risk-benefit profiles for therapeutic options in pulmonary arterial hypertension (PAH). A grading system for the level of evidence of treatments based on the controlled clinical trials performed with each compound is used to propose an evidence-based treatment algorithm. The algorithm includes drugs approved by regulatory agencies for the treatment of PAH and/or drugs available for other indications. The different treatments have been evaluated mainly in idiopathic PAH, heritable PAH, and in PAH associated with the scleroderma spectrum of diseases or with anorexigen use. Extrapolation of these recommendations to other PAH subgroups should be done with caution. Oral anticoagulation is proposed for most patients; diuretic treatment and supplemental oxygen are indicated in cases of fluid retention and hypoxemia, respectively. High doses of calcium-channel blockers are indicated only in the minority of patients who respond to acute vasoreactivity testing. Nonresponders to acute vasoreactivity testing or responders who remain in World Health Organization (WHO) functional class III, should be considered candidates for treatment with either an oral phosphodiesterase-5 inhibitor or an oral endothelin-receptor antagonist. Continuous intravenous administration of epoprostenol remains the treatment of choice in WHO functional class IV patients. Combination therapy is recommended for patients treated with PAH monotherapy who remain in WHO functional class III. Atrial septostomy and lung transplantation are indicated for refractory patients or where medical treatment is unavailable.

Domiciliary oxygen for children

Domiciliary oxygen is used increasingly in pediatric practice, and the largest patient group to receive it is ex-premature babies with chronic neonatal lung disease. Because of a scarcity of good evidence to inform clinicians, there is a lack of consensus over many issues, even those as fundamental as the optimum target oxygen saturation. Nevertheless, many children benefit from receiving supplemental oxygen at home, particularly because it helps to keep them out of the hospital.

Safety and efficacy of autologous endothelial progenitor cells transplantation in children with idiopathic pulmonary arterial hypertension: open-label pilot study

Experimental data suggest that transplantation of EPCs attenuates monocrotaline-induced pulmonary hypertension in rats and dogs. In addition, our previous studies suggested that autologous EPC transplantation was feasible, safe, and might have beneficial effects on exercise capacity and pulmonary hemodynamics in adults with IPAH. Thus, we hypothesized that transplantation of EPCs would improve exercise capacity and pulmonary hemodynamics in children with IPAH. Thirteen children with IPAH received intravenous infusion of autologous EPCs. The right-sided heart catheterization and 6-MWD test were performed at baseline and at the time of 12 wk after cell infusion. At the time of 12 wk, mPAP decreased by 6.4 mmHg from 70.3 +/- 19.0 to 63.9 +/- 19.3 mmHg (p = 0.015). PVR decreased by approximately 19% from 1118 +/- 537 to 906 +/- 377 dyn s/cm(5) (p = 0.047). CO increased from 3.39 +/- 0.79 to 3.85 +/- 0.42 L/min (p = 0.048). The 6-MWD increased by 39 m from 359 +/- 82 to 399 +/- 74 m (p = 0.012). NYHA functional class also improved. There were no severe adverse events with cell infusion. The small pilot study suggested that intravenous infusion of autologous EPCs was feasible, safe, and associated with significant improvements in exercise capacity, NYHA functional class, and pulmonary hemodynamics in children with IPAH. Confirmation of these results in a randomized controlled trial are essential.

Endothelin receptor antagonists improve exercise tolerance and oxygen saturations in patients with Eisenmenger syndrome and congenital heart defects

Patients with Eisenmenger syndrome experience substantial morbidity and decreased survival rates. In advanced cases, lung transplantation with cardiac repair or heart-lung transplantation is often the only option. The efficacy of endothelin receptor antagonists in Eisenmenger syndrome, which has similar pathophysiology to idiopathic pulmonary hypertension, remains unknown.We retrospectively studied adults with congenital heart disease and Eisenmenger syndrome who were treated with endothelin receptor antagonists. Analysis included chart reviews of clinical evaluations, oxygen saturation levels, functional class, 6-minute walk distances, and pulmonary artery pressures. In the 24 patients studied, Eisenmenger syndrome was caused by ventricular septal defect (6 patients), atrial septal defect (5), atrioventricular canal defect (3), complex congenital heart disease (9), and patent ductus arteriosus (1).Eisenmenger syndrome was treated with bosentan (21 patients) and sitaxsentan (3 patients). On average, therapy lasted 19 +/- 12 months. Subsequently, mean 6-minute walk distances improved from 226 +/- 159 m to 351 +/- 113 m (P = 0.004), and World Health Organization functional class improved > or =1 grade (P < 0.0001). Oxygen saturations increased on therapy from 80.5% to 87% (P < 0.0001). Pulmonary arterial systolic pressures decreased from 97 +/- 21 mmHg to 78 +/- 27 mmHg, and mean pressures from 59 +/- 16 mmHg to 47 +/- 17 mmHg (both P < 0.0001). Neither major complications from therapy nor changes in pulmonary capillary wedge pressure occurred.Endothelin receptor antagonists may play an important role in improving 6-minute walk distance, oxygen saturation, pulmonary artery pressures, and symptoms in adults who have congenital heart defects and Eisenmenger syndrome.

Treatment of patients with Eisenmenger's syndrome with Bosentan

We treated prospectively 14 patients with Eisenmenger's syndrome, with a mean age of 10 years, ranging from 3 to 18 years. Treatment continued for 12 months, and demonstrated a lasting symptomatic improvement, but no improvement in terms of mean saturation of oxygen over 24 hours. Exercise capacity, as judged by peak uptake of oxygen, worsened in the six patients able to perform a treadmill test. The symptomatic benefit from dual blockage of endothelin receptors in these patients may be due to mechanisms other than selective pulmonary vasodilatation alone.

Standard therapies for pulmonary arterial hypertension

After half a century of clinical experience and research, management of pulmonary arterial hypertension remains a challenge. Currently, data to support the use of standard therapies for pulmonary arterial hypertension (oxygen supplementation, diuretics, digoxin, anticoagulation, and calcium channel blockers) are mostly retrospective, uncontrolled prospective, or derived from other diseases with similar but not identical manifestations. In the absence of any further prospective, controlled studies, it is reasonable to use these therapies when they are tolerated. When these therapies are poorly tolerated, however, the threshold for discontinuation should be low.

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.

Bosentan for the treatment of pulmonary arterial hypertension associated with congenital cardiac disease

AIMS

Bosentan is efficacious in idiopathic pulmonary arterial hypertension, and the variants associated with connective tissue disease, but not currently approved for treatment of pulmonary arterial hypertension due to Eisenmenger's syndrome. We sought to evaluate its effect in adults with Eisenmenger's syndrome.

METHODS

We administered bosentan on the basis of compassionate use in 23 patients with Eisenmenger's syndrome, aged 37 plus or minus 14 years. Of the patients, 17 had never received specific treatment for pulmonary arterial hypertension, five were transitioned from treprostinil, and one from beraprost to bosentan. We measured functional class, saturation of oxygen, haemoglobin levels and six-minute walk distance at baseline, one, six months and at most recent follow-up.

RESULTS

Baseline functional class was IV in three, III in fifteen, and II in five patients. At follow-up, with a mean of 15 plus or minus 10 months, 13 of the 23 patients (57%) had improved by at least one functional class, from a median baseline of III to II (p equal to 0.016), mean saturation of oxygen at rest had increased from 81% to 84% (p equal to 0.001), and levels of haemoglobin had decreased from 178 plus or minus 26 grams per litre to 167 plus or minus 19 grams per litre (p equal to 0.001). Overall, the six-minute walk distance did not change from baseline of 335 metres. The distance walked by those not previously receiving specific therapy, however, improved from 318 plus or minus 129 to 345 plus or minus 123 metres (p equal to 0.03).

CONCLUSION

Treatment of adults with Eisenmenger's syndrome using bosentan significantly improved functional class, saturation of oxygen at rest, and decreased levels of haemoglobin. Treatment with bosentan was associated with improvement in six-minute walk distance in those not previously receiving specific therapy. In patients already in receipt of specific therapy, transition to bosentan resulted in no clinical deterioration.

Eisenmenger syndrome: medical prevention and management strategies

The original definition of Eisenmenger syndrome refers to an unrestrictive post-tricuspid valve congenital systemic-to-pulmonary shunt. When the pulmonary arterial systolic pressure becomes equal to the systemic arterial systolic pressure, the direction of the shunt becomes pulmonary-to-systemic. The latter leads to progressive cyanosis, and exercise intolerance is initially proportional to the degree of hypoxaemia. Later, congestive heart failure may occur . The management principle is to avoid any factors that destabilise this delicately balanced physiology. Until recently, this could only be achieved by symptomatic therapy; however, when patients are severely incapacitated, transplantation is needed. At present, new drugs, which are more selective pulmonary vasodilators, are available to interfere with the ongoing disease process to improve functional capacity and delay the decision for transplantation.

Safety and efficacy of Sildenafil therapy in children with pulmonary hypertension

OBJECTIVE

Sildenafil is a selective Phosphodiesterase-5 inhibitor that has been reported to be a potent pulmonary vasodilator. We evaluated the safety, efficacy and pharmacokinetics of oral Sildenafil in a case series of children with pulmonary hypertension.

METHODS

Three children, 1 with primary pulmonary hypertension (patient 1) and 2 with pulmonary hypertension associated with congenital heart disease (patients 2 and 3) were enrolled. Sildenafil was started at 0.5 mg/kg 4-hourly and the dose increased to 1.0 and then to 2.0 mg/kg/dose. Patients were assessed at baseline and then monthly for a total of 6 visits.

RESULTS

All patients reported increased exercise capacity with improvement in New York Heart Association functional class. The distance walked during the 6-min test increased by 74% (patient 1), 75% (patient 2) and 25% (patient 3) and oxyhaemoglobin saturations increased from 79%, 97% and 80% to 93%, 100% and 93%, respectively. There were no side effects and no fall in systemic blood pressure. Sildenafil plasma levels 1 h after a 0.5, 1.0 and 2 mg/kg dose of Sildenafil were 109+/-87, 150+/-62 and 368+/-200 ng/ml, respectively. They fell to 211+/-106 ng/ml 3 h after the 2.0 mg/kg dose.

CONCLUSIONS

Medium term Sildenafil therapy improves oxyhaemoglobin saturations and exercise tolerance in children with pulmonary hypertension without any side effects. Mean plasma levels 1 h after doses of 0.5-2.0 mg/kg are similar to the maximum plasma concentrations reported in adults receiving doses within the therapeutic range. Sildenafil use in children appears to be safe and may be beneficial in the management of pulmonary arterial hypertension.

Home oxygen for children: who, how and when?

A review of the specific requirements of home oxygen therapy in children which attempts to offer guidance to clinicians and service providers.

Initial experience with bosentan therapy in patients with the Eisenmenger syndrome

Bosentan, an endothelin-1 antagonist that can be administered orally, has been shown to be effective in the treatment of idiopathic pulmonary arterial hypertension and may be of benefit to patients with the Eisenmenger syndrome. Nine patients with Eisenmenger's syndrome were treated with bosentan at a dose of 125 mg twice a day. After treatment with bosentan, 6 of 9 patients (67%) had an improvement in New York Heart Assocation classification of >/=1 grades (p = 0.03). Oxygen saturation levels increased from 79 +/- 5% to 88 +/- 6%, (p = 0.03). The side effects of bosentan therapy were minor; no significant changes in liver function tests were noted. These preliminary data suggest that oral administration of bosentan therapy for Eisenmenger's syndrome results in improved oxygenation and functional status with minimal side effects.

Pulmonary arterial hypertension in children

Pulmonary arterial hypertension is a serious progressive condition with a poor prognosis if not identified and treated early. Because the symptoms are nonspecific and the physical findings can be subtle, the disease is often diagnosed in its later stages. Remarkable progress has been made in the field of pulmonary arterial hypertension over the past several decades. The pathology is now better defined, and significant advances have occurred in understanding the pathobiologic mechanisms. Risk factors have been identified, and the genetics have been characterized. Advances in technology allow earlier diagnosis as well as better assessment of disease severity. Therapeutic modalities such as new drugs, e.g., epoprostenol, treprostinil, and bosentan, and surgical/interventional options, e.g., transplantation and atrial septostomy, which were unavailable several decades ago, have had a significant impact on prognosis and outcome. Thus, despite our inability to cure pulmonary arterial hypertension, advances in medical treatments over the past two decades have resulted in significant improvement in outcomes for children with various forms of pulmonary arterial hypertension. This report is a review the current state of the art for pulmonary arterial hypertension in 2004, with an emphasis on childhood pulmonary arterial hypertension and specific recommendations for current practice and future directions.

Eisenmenger's syndrome: current management

Eisenmenger's syndrome describes the elevation of pulmonary arterial pressure to the systemic level caused by increased pulmonary vascular resistance with reversal or bi-directional shunting through a large intracardiac or extracardiac congenital heart defect. This article reviews the natural history and pathophysiology of Eisenmenger's syndrome untreated and medical and surgical treatment options presently available. Although there is no cure for this condition at present, recent advances in management have improved the quality of life for many patients with Eisenmenger's syndrome.

Medical therapy of pulmonary hypertension. An overview of treatment and goals

Therapeutic medical advances over the past two decades have resulted in significant improvements in the outcome for patients with various forms of pulmonary arterial hypertension. As the current understanding of the pathology and pathobiology of pulmonary arterial hypertension has moved forward, rationale for additional therapeutic modalities with novel therapeutic agents has led to increased clinical investigations. A brief overview of the pathology and pathobiology is presented as background for an introduction to the current medical therapy for pulmonary arterial hypertension as well as the goals for future treatment.

Clinical classification of pulmonary hypertension

Pulmonary hypertension is a prevalent disease of multiple etiologies. Over the years, different attempts at nomenclature and classification, largely based on morphologic findings at autopsy, have met with limited success. Recent advances in medical and surgical treatment, and the promise of effective approaches to prevention, have prompted the development of a clinical classification designed to take advantage of the new promising interventions. This article traces the growth of understanding of the pulmonary hypertensive diseases that has enabled the development of a clinical classification oriented towards prevention and treatment.

Eisenmenger Syndrome

The incidence of congenital cardiovascular malformation is unknown but is estimated to be approximately 0.8% of live births. This figure does not include preterm infants (all of whom have a patent ductus arteriosus [PDA]) or stillborn infants (who have a high incidence of cardiovascular abnor malities). Approximately 9% of patients with congenital car diac disease and 11% of those with uncorrected left-to-right intracardiac shunts will develop the Eisenmenger syndrome (ES). ES develops at different rates, depending on the size and location of the cardiac lesion and the amount of in creased pulmonary blood flow and pressure. Onset in in fancy is common in patients with PDA or a large ventricular septal defect (VSD). ES is seen in up to 50% of patients with VSD larger than 1.5 cm in diameter, whereas there is only a 3% incidence in those with defects that are less than 1.5 cm in diameter. Children with Down syndrome and a VSD or atrioventricular canal defect are prone to early development of ES. They have abnormal upper airways that predispose them to chronic upper airway obstruction and sleep apnea, both of which promote hypoxemia, hypercarbia, and early development of pulmonary hypertension. ES develops early in nearly all patients with uncorrected transposition of the great arteries and truncus arteriosus, whereas most patients with uncorrected ASD who develop the syndrome do so in the second decade of life. The prognosis for survival through childhood with ES is relatively good. Patients usually lead remarkably active lives until shortly before they die. The goal of this article is to provide a detailed overview of the pathophysiology, clinical presentation, and medical and sur gical management of these patients. Particular focus on the anesthetic management of patients undergoing cardiac and noncardiac surgery is provided.

Eisenmenger's Syndrome

In general, most authors advocate nonintervention in Eisenmenger's syndrome, but an awareness of potential palliative measures to avoid destabilizing a delicately balanced physiology is needed as well. This approach has failed to alter long-term outcome, however. Survival for patients with Eisenmenger's syndrome has not improved substantially in the past several decades. Quality of life is universally altered by the presence of cyanosis, exercise intolerance, and the comorbid conditions associated with erythrocytosis. We therefore believe that the use of novel alternatives, as they become available, is warranted and that these alternatives are likely to be best evaluated in multicenter collaborative trials. The approach to the patient with pulmonary vascular obstructive disease (PVOD) should begin with maximization of palliative therapy and should, as compliance and teaching are ensured, proceed to the use of therapies designed to reverse the underlying proliferative changes in the pulmonary vasculature. Frequent checking of potential supplemental oxygen responsiveness and use of inhaled oxygen as needed to maximize systemic arterial saturation should be considered, although evidence of the value of home oxygen use is currently lacking. We favor systemic anticoagulation to a target international normalized ratio of 2.0 to 2.5. There are currently no published data supporting this practice in patients with PVOD, but we believe that as in patients with primary pulmonary hypertension, benefit is likely to outweigh risk. In the setting of a meticulous outpatient anticoagulation service, we have witnessed acceptably low bleeding event rates. A controlled clinical trial is warranted. Selective pulmonary vasodilators and antiproliferative agents hold significant promise in altering the natural history of PVOD associated with intracardiac shunting. The risk of paradoxic embolism and the theoretical worsening of right- to-left shunting compound the already high risk of systemically administered therapies; neither, to date, has been limiting in our patients. Studies of infused or newer subcutaneous and inhaled formulations are under way, and preliminary experience suggests real benefit--improved hemodynamics, improved exercise tolerance, and increased systemic arterial saturation--in this group of patients. Lung transplantation still trades a disease for another set of problems associated with long-term immunosuppression and chronic graft rejection in patients with previous sternotomy and thoracotomy and with a high acute surgical risk. Population studies of mortality and morbidity in patients with PVOD associated with congenital heart disease who receive transplants do not seem to suggest significant improvement with this therapy. In the future, the management of Eisenmenger's syndrome will probably include a multipharmacologic approach that targets several factors in the inflammatory cascade leading to vascular proliferation, perhaps offered in concert with novel surgical or transcatheter strategies designed to limit intracardiac shunting and, if desired, provide complete repair of intracardiac defects.

Effect of body position changes on pulmonary gas exchange in Eisenmenger's syndrome

Preliminary studies on sleep of patients with congenital heart disease and Eisenmenger's syndrome (ES) at our institution demonstrated nocturnal worsening arterial unsaturation, which appeared to be a body position-related phenomenon. To investigate the potential effect of body position on gas exchange in ES, we carried out a prospective study of 28 patients (mean age, 34.8 +/- 11.7 yr) with established ES due to congenital heart disease. In every patient, arterial blood gases were performed during both sitting and supine positions under three different conditions: room air, while breathing 100% oxygen, and after breathing oxygen at a flow rate of 3 L/min through nasal prongs. Alveolar oxygen pressure (PaO2) for the calculation of alveolar-arterial oxygen tension differences (AaPO2) was derived from the alveolar gas equation using PaCO2 and assuming R = 1. We used paired t test, repeated-measures two-way ANOVA with Bonferroni's test, and regression analysis. From sitting to supine position on room air, there was a significant decrease in PaO2 (from 52.5 +/- 7.5 to 47.5 +/- 5.5 mm Hg; p < 0. 001) and SaO2 (from 86.7 +/- 4.6 to 83.3 +/- 4.9%; p < 0.001), both of which were corrected by nasal O2 (to 68.2 +/- 21 mm Hg and to 92 +/- 4%, respectively, p < 0.005). PaCO2 and pH remained unchanged. The magnitude of the change in PaO2 correlated with the change in AaPO2 on room air (r = 0.77; p < 0.01) but not with the change in AaPO2 on 100% oxygen. It is concluded that in adult patients with ES there is a significant decrease in PaO2 and SaO2 when they change from the sitting to the supine position. A ventilation-perfusion (V/Q) distribution abnormality and/or a diffusion limitation phenomenon rather than an increase in true shunt may be the mechanisms responsible for this finding. The response to nasal O 2 we observed warrants a trial with long-term nocturnal oxygen therapy in these patients.

Recent advances in the treatment of pediatric pulmonary artery hypertension

As our understanding of the pathogenesis of PAH evolves, newer strategies for its treatment are being developed and implemented. Based on studies with adult PPH patients, anticoagulation is now regarded as a mainstay of therapy and is associated with prolonged survival. Before the era of vasodilator therapy, which began in the late 1970s, most children with PPH died within 1 year of diagnosis. Now with chronic calcium channel blockade, survival and QOL are improved in children who acutely respond to vasodilator drug testing. In the author's experience, the 5-year survival rate for patients treated with chronic oral calcium channel blockade who respond acutely to vasodilator testing is 97% versus 35% for those who do not respond acutely. Continuous i.v. prostacyclin has also been used successfully, with a 5-year survival rate of 92% in children in whom oral calcium channel blockade failed (although in some patients the prostacyclin therapy was used as a bridge to transplantation) versus 29% in children in whom oral calcium channel blockade also failed and for whom chronic prostacyclin was unavailable. Before the availability of long-term prostacyclin therapy, 30% to 40% of patients with PPH died while waiting for transplantation. Prostacyclin has virtually eliminated this situation. The results of lung transplantation for adult patients with PPH at 3 years are similar to the results of those on continuous i.v. prostacyclin. Ultimately, the best therapy for an individual child depends on the results of longer follow-up studies. Inhaled nitric oxide has also been used to treat PAH in newborns and other forms of acute and chronic PAH. Although less experience exists with long-term inhaled nitric oxide than with long-term prostacyclin, the preliminary results of long-term inhaled nitric oxide are promising and await further study. The "optimal" vasodilator for long-term therapy, (e.g., calcium channel blockade), prostacyclin, nitric oxide, or potential future therapies, such as prostacyclin analogs, endothelin receptor blockers and thromboxane synthase inhibitors or receptor blockers, must be based on a thorough evaluation with acute vasodilator testing and overall risk-benefit considerations for the various therapeutic regimens. Further clarification of the mechanisms of the development and perpetuation of the PAH process will undoubtedly lead to a refinement in treatment strategies for patients with PAH, which not too long ago was often considered untreatable and fatal. By increasing our understanding of the pathogenesis and pathophysiology of primary and secondary PAH disorders, one day we may be able to prevent or cure these diseases as opposed to providing only palliative therapy. Despite this, therapeutic advances have significantly improved the outcome for children with PAH.