Effects of low doses of inhaled nitric oxide combined with oxygen for the evaluation of pulmonary vascular reactivity in patients with pulmonary hypertension

Research Progress on Pulmonary Arterial Hypertension and the Role of the Angiotensin Converting Enzyme 2-Angiotensin-(1-7)-Mas Axis in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease with a complex aetiology and high mortality. Functional and structural changes in the small pulmonary arteries lead to elevated pulmonary arterial pressure, resulting in right heart failure. The pathobiology of PAH is not fully understood, and novel treatment targets in PAH are desperately needed. The renin-angiotensin system is critical for maintaining homeostasis of the cardiovascular system. The system consists of the angiotensin converting enzyme (ACE)-angiotensin (Ang) II-angiotensin type 1 receptor (AT₁R) axis and the ACE2-Ang-(1-7)-Mas receptor axis. The former, the ACE-Ang II-AT₁R axis, is involved in vasoconstrictive and hypertensive actions along with cardiac and vascular remodelling. The latter, the ACE2-Ang-(1-7)-Mas axis, generally mediates counterbalancing effects against those mediated by the ACE-Ang II-AT₁R axis. Based on established functions, the ACE2-Ang-(1-7)-Mas axis may represent a novel target for the treatment of PAH. This review focuses on recent advances in pulmonary circulation science and the role of the ACE2-Ang-(1-7)-Mas axis in PAH.

Noninvasive Administration of Inhaled Nitric Oxide and its Hemodynamic Effects in Patients With Acute Right Ventricular Dysfunction

OBJECTIVE

The authors aimed to assess the hemodynamic effects and demonstrate the feasibility of inhaled nitric oxide (iNO) in hemodynamically unstable patients with acute right ventricular (RV) dysfunction and to explore the safety profile of this approach.

DESIGN

Retrospective cohort study.

SETTING

Intensive care unit (ICU) of 2 tertiary care centers between January 2013 and 2017.

PARTICIPANTS

All patients with RV dysfunction in whom iNO was initiated without invasive mechanical ventilation.

INTERVENTION

Noninvasive administration of iNO.

MEASUREMENTS AND MAIN RESULTS

Eighteen patients received the intervention during the study period; 8 of these patients had a pulmonary artery catheter and 2 had a pulse contour analysis device. Median (interquartile range) iNO concentration was 20 (20-20) ppm, and therapy duration was 24 (12-46) hours. Most patients received iNO through nasal prongs (66.7%) or a high-flow nasal cannula (27.8%). Within 1 hour, iNO reduced pulmonary vascular resistance from 219.1 to 165.4 dyn•s/cm⁵ (n = 7; p < 0.001), mean pulmonary artery pressure from 28.4 to 25.3 mmHg (n = 8; p = 0.01), and central venous pressure from 17.5 to 13.1 mmHg (n = 16; p = 0.001). Indexed cardiac output increased from 2.0 to 2.6 L/min/m² (n = 9; p = 0.004). ICU mortality was 27.78%, and median ICU length of stay was 7 (5-9) days. Two significant bleeding episodes requiring intervention and 1 acute kidney injury occurred during iNO therapy. No headache was reported.

CONCLUSION

Noninvasively administered iNO was associated with favorable hemodynamic effects in ICU patients with acute RV dysfunction. These results suggest the safety and feasibility of this therapy for which further prospective study is warranted.

Clinical recommendations for postoperative care after heart transplantation in children: 21 years of a single-center experience

Heart transplantation is an option for children with complex congenital heart disease and cardiomyopathies. A patient's quality of life and long-term survival depend on successful management of the surgical complications and adverse side effects of immunosuppression. The purpose of this review was to summarize the practical management of postoperative care in this patient population and to make recommendations for the future.

Endothelial cell energy metabolism, proliferation, and apoptosis in pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a fatal disease characterized by impaired regulation of pulmonary hemodynamics and excessive growth and dysfunction of the endothelial cells that line the arteries in PAH lungs. Establishment of methods for culture of pulmonary artery endothelial cells from PAH lungs has provided the groundwork for mechanistic translational studies that confirm and extend findings from model systems and spontaneous pulmonary hypertension in animals. Endothelial cell hyperproliferation, survival, and alterations of biochemical-metabolic pathways are the unifying endothelial pathobiology of the disease. The hyperproliferative and apoptosis-resistant phenotype of PAH endothelial cells is dependent upon the activation of signal transducer and activator of transcription (STAT) 3, a fundamental regulator of cell survival and angiogenesis. Animal models of PAH, patients with PAH, and human PAH endothelial cells produce low nitric oxide (NO). In association with the low level of NO, endothelial cells have reduced mitochondrial numbers and cellular respiration, which is associated with more than a threefold increase in glycolysis for energy production. The shift to glycolysis is related to low levels of NO and likely to the pathologic expression of the prosurvival and proangiogenic signal transducer, hypoxia-inducible factor (HIF)-1, and the reduced mitochondrial antioxidant manganese superoxide dismutase (MnSOD). In this article, we review the phenotypic changes of the endothelium in PAH and the biochemical mechanisms accounting for the proliferative, glycolytic, and strongly proangiogenic phenotype of these dysfunctional cells, which consequently foster the panvascular progressive pulmonary remodeling in PAH.

Deficiency of lung antioxidants in idiopathic pulmonary arterial hypertension

Idiopathic pulmonary arterial hypertension (IPAH) is associated with lower levels of the pulmonary vasodilator nitric oxide (NO) and its biochemical reaction products (nitrite [NO(2) (-)], nitrate [NO(3) (-)]), in part, due to the reduction in pulmonary endothelial NO synthesis. However, NO levels are also determined by consumptive reactions, such as with superoxide to form peroxynitrite, which subsequently may generate stable products of nitrotyrosine (Tyr-NO(2)) and/or NO(3) (-). In this context, superoxide dismutase (SOD) preserves NO in vivo by scavenging superoxide and preventing the consumptive reactions. Here, we hypothesized that reactive oxygen species (ROS) consumption of NO may contribute to the low NO level and development of pulmonary hypertension. To test this, nitrotyrosine and antioxidants glutathione (GSH), glutathione peroxidase (GPx), catalase, and SOD were evaluated in IPAH patients and healthy controls. SOD and GPx activities were decreased in IPAH lungs (all p < 0.05), while catalase and GSH activities were similar among the groups (all p > 0.2). SOD activity was directly related to exhaled NO (eNO) (R(2)= 0.72, p= 0.002), and inversely related to bronchoalveolar lavage (BAL) NO(3) (-) (R(2)=-0.73, p= 0.04). Pulmonary artery pressure (PAP) could be predicted by a regression model incorporating SOD, GPx, and NO(3) values (R(2)= 0.96, p= 0.01). These findings suggest that SOD and GPx are associated with alterations in NO and PAP in IPAH.

Teste de vasorreatividade pulmonar

A hipertensão arterial pulmonar é classificada como idiopática ou secundária (associada a colagenoses, cardiopatias, hipertensão portal, tromboembolismo pulmonar e doenças da vasculatura pulmonar). O teste de vasorreatividade pulmonar é indicado para definir a melhor opção terapêutica. Muitas drogas têm sido utilizadas para a realização desse teste, sendo o óxido nítrico inalado a melhor opção, por apresentar ação específica pulmonar e meia vida muita curta (5-10 s). O resultado desse teste identifica candidatos à cirurgia cardíaca nas cardiopatias congênitas e candidatos ao uso de antagonista de cálcio nas outras formas de hipertensão pulmonar. A realização e interpretação do teste de vasorreatividade pulmonar exigem grande responsabilidade, e erros podem levar a decisões erradas e à ocorrência de óbitos.

Comparison of the effectiveness of oral sildenafil versus oxygen administration as a test for feasibility of operation for patients with secondary pulmonary arterial hypertension

It is shown that phosphodiesterase type 5 (PDE5) inhibitors such as sildenafil can modulate pulmonary arterial hypertension (PAH) via increasing the level of guanosine-3,5-cyclic monophosphate (cGMP) and decreases pulmonary artery pressure (PAP). In this study we determined the effectiveness of sildenafil and compared its efficacy with inhaled nasal oxygen (O2) during cardiac catheterization in patients with congenital heart diseases (CHD) and PAH, as a test of feasibility for surgical repair of the patients. We studied 15 patients, 9 male and 6 female, with a mean age of 8.3 years. Hemodynamic measurements were made at baseline, after O2 administration for 20 min (5 L/min by mask), and then 45 min after administration of a single dose of sildenafil (0.5 mg/kg orally or via nasogastric tube). Mean PAP at baseline was 72.2 +/- 12.54 mm Hg and was reduced by sildenafil to 52.5 +/- 9.6 and by O2 to 61.3 +/- 10.39. Both sildenafil and O2 decreased PAP effectively (p = 0.08 and p = 0.04, respectively). Pulmonary vascular resistance (PVR) was calculated for 12 patients, with a baseline level of 9.08 +/- 1.09 mm Hg . L(-1) . min, which was significantly decreased by O2, to 3.74 +/- 0.43, and by sildenafil, to 5.93 +/- 0.75 (p = 0.005 and p = 0.05, respectively). Sildenafil, as a single oral dose, can effectively reduce PAP and PVR. This novel PDE5 inhibitor can be used for assessment of feasibility of operation for patients with CHD and PAH when inhaled NO is not available.

Alterations of cellular bioenergetics in pulmonary artery endothelial cells

Idiopathic pulmonary arterial hypertension (IPAH) is pathogenetically related to low levels of the vasodilator nitric oxide (NO). Because NO regulates cellular respiration and mitochondrial biogenesis, we hypothesized that abnormalities of bioenergetics may be present in IPAH. Evaluation of pulmonary artery endothelial cells from IPAH and control lungs in vitro revealed that oxygen consumption of IPAH cells was decreased, especially in state 3 respiration with substrates glutamate-malate or succinate, and this decrease paralleled reduction in Complex IV activity and IPAH cellular NO synthesis. IPAH pulmonary artery endothelial cells had decreased mitochondrial dehydrogenase activity and lowered mitochondrial numbers per cell and mitochondrial DNA content, all of which increased after exposure to NO donors. Although IPAH/pulmonary artery endothelial cells' ATP content was similar to control under normoxia, cellular ATP did not change significantly in IPAH cells under hypoxia, whereas ATP decreased 35% in control cells, identifying a greater dependence on cellular respiration for energy in control cells. Evidence that glucose metabolism was subserving the primary role for energy requirements of IPAH cells was provided by the approximately 3-fold greater glycolytic rate of IPAH cells. Positron emission tomography scan with [18F]fluoro-deoxy-D-glucose performed on IPAH patients and healthy controls revealed significantly higher uptake in IPAH lungs as compared with controls, confirming that the glycolytic rate was increased in vivo. Thus, there are substantial changes in bioenergetics of IPAH endothelial cells, which may have consequences for pulmonary hypertensive responses and potentially in development of novel imaging modalities for diagnosis and evaluation of treatment.

Simplified pulmonary vasodilatory testing in the cardiac catheterization laboratory with nasal cannula nitric oxide

In patients with pulmonary hypertension, pulmonary vasodilator testing with inhaled nitric oxide (NO) during cardiac catheterization provides valuable data for defining future care plans. Previously, the use of delivery systems for spontaneously breathing individuals required a tight-fitting seal by face mask and an approved delivery and dilution device. We hypothesized that a simplified delivery system using nasal cannula could be utilized to effectively deliver NO during cardiac catheterization. We developed a simple delivery system to deliver through a nasal cannula a concentration of NO at 50 ppm at the nares along with supplemental oxygen (O2) via face tent. We prospectively employed this system for 10-minute intervals on 11 patients (age range, 7 months to 41 years) with pulmonary hypertension undergoing scheduled cardiac catheterization. Mean pulmonary artery pressure (PAp) decreased from 62 mmHg (range, 38-99) at room air testing to 45 mmHg (range, 36-91) with the addition of NO plus O2 (p = 0.014). Pulmonary vascular resistance (PVR) decreased from 11.6 U.m2 (range, 4.5-43.4) to 6.3 U.m2 (range, 2.0-34.2) (p = 0.001). A response of 20% or more reduction in PVR was seen in all 11 patients. The initial ratio of pulmonary to systemic vascular resistance (Rp:Rs) was 0.49 (range, 0.25-3.5) and decreased to 0.35 (range 0.1-2.6) (p = 0.002). No adverse side effects were noted. We found this NO delivery system to be a simple and effective method of pulmonary vasodilatory testing that may have wide applicability in the cardiac catheterization laboratory.

Nitric oxide in the evaluation of congenital heart disease with pulmonary hypertension: factors related to nitric oxide response

Inhaled nitric oxide (NO) has been used in the preoperative evaluation of patients with congenital heart disease and pulmonary hypertension. The purpose of this study was to characterize responses in pulmonary vascular resistance (PVR) to oxygen and increasing doses of NO during cardiac catheterization and to determine if any related factors affect the response of the pulmonary vascular bed to NO. A prospective analysis of 42 patients (median age, 3.0 years) with congenital heart disease and pulmonary hypertension who underwent NO testing was performed. Systemic vascular resistance (SVR) and PVR were assessed in room air, 100% oxygen, and oxygen plus 20, 40, and 80 parts per million (ppm) NO. Changes in pulmonary artery pressure, PVR, and SVR were assessed. The response to NO was then correlated to individual patient's age, gender, type of heart defect, the presence of trisomy 21, and baseline PVR/SVR. There was a greater decrease in PVR and PVR/SVR with 20 ppm NO than with oxygen alone. There was no additional decrease at 40 or 80 ppm NO. There was no correlation between age, gender, type of congenital heart disease, and baseline PVR/SVR ratio with the degree of response to NO. Patients with trisomy 21 had less of a response to NO (p = 0.017) than patients without trisomy 21. There is no difference in determining PVR response with doses of NO beyond 20 ppm during cardiac catheterization. Age, gender, and baseline PVR/SVR ratio are not associated with responsiveness to NO. Patients with trisomy 21 may be less responsive to NO.

Increased arginase II and decreased NO synthesis in endothelial cells of patients with pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH), a fatal disease of unknown etiology characterized by impaired regulation of pulmonary hemodynamics and vascular growth, is associated with low levels of pulmonary nitric oxide (NO). Based upon its critical role in mediating vasodilation and cell growth, decrease of NO has been implicated in the pathogenesis of PAH. We evaluated mechanisms for low NO and pulmonary hypertension, including NO synthases (NOS) and factors regulating NOS activity, i.e. the substrate arginine, arginase expression and activity, and endogenous inhibitors of NOS in patients with PAH and healthy controls. PAH lungs had normal NOS I-III expression, but substrate arginine levels were inversely related to pulmonary artery pressures. Activity of arginase, an enzyme that regulates NO biosynthesis through effects on arginine, was higher in PAH serum than in controls, with high-level arginase expression localized by immunostaining to pulmonary endothelial cells. Further, pulmonary artery endothelial cells derived from PAH lung had higher arginase II expression and produced lower NO than control cells in vitro. Thus, substrate availability affects NOS activity and vasodilation, implicating arginase II and alterations in arginine metabolic pathways in the pathophysiology of PAH.

Recent advances in the treatment of pulmonary hypertension

PURPOSE OF REVIEW

Pulmonary hypertension is a debilitating life-threatening disease of all ages. The long-term prognosis can be dismal despite maximal medical therapy. There have been significant advances in our understanding of the pathobiology and genetics of this disease, and novel pharmacological approaches appear to offer promising alternatives to conventional therapy. Anesthesiologists have been instrumental in the development and widespread clinical introduction of inhaled nitric oxide. Unfortunately, despite early optimism, inhaled nitric oxide has several significant limitations related to its cost, toxicity, required complex technology, and occasional therapeutic failure. Therefore, there is a need for an effective alternative pulmonary vasodilator. The early diagnosis and treatment of pulmonary hypertension are crucial if improvements are to be realized. This review will present recent work in this field in an attempt to increase anesthesiologists' awareness of potential new treatment options.

RECENT FINDINGS

Emerging data concerning the genetics of certain pulmonary hypertension variants have provided insight into the pathobiology of this disease and may lead to advances in the early detection or new treatment options. New pharmacological approaches include drugs such as nitric oxide donors, phosphodiesterase inhibitors, endothelin antagonists, and prostacyclin analogues. Attention has also been focused on the use of combinations of drugs of different classes.

SUMMARY

The clinical outcome of pulmonary hypertension is dependent upon early detection and therapy. Increased awareness of current therapeutic options will facilitate earlier effective treatment.

Pediatric cardiac postoperative care

The Heart Institute of the University of São Paulo, Medical School is a referral center for the treatment of congenital heart diseases of neonates and infants. In the recent years, the excellent surgical results obtained in our institution may be in part due to modern anesthetic care and to postoperative care based on well-structured protocols. The purpose of this article is to review unique aspects of neonate cardiovascular physiology, the impact of extracorporeal circulation on postoperative evolution, and the prescription for pharmacological support of acute cardiac dysfunction based on our cardiac unit protocols. The main causes of low cardiac output after surgical correction of heart congenital disease are reviewed, and methods of treatment and support are proposed as derived from the relevant literature and our protocols.