The biological role and future therapeutic uses of nitric oxide in extracorporeal membrane oxygenation, a narrative review.

BACKGROUND: Nitric oxide (NO) is a gas naturally produced by the human body that plays an important physiological role. Specifically, it binds guanylyl cyclase to induce smooth muscle relaxation. NO's other protective functions have been well documented, particularly its protective endothelial functions, effects on decreasing pulmonary vascular resistance, antiplatelet, and anticoagulation properties. The use of nitric oxide donors as vasodilators has been known since 1876. Inhaled nitric oxide has been used as a pulmonary vasodilator and to improve ventilation perfusion matching since the 1990s. It is currently approved by the United States Food and Drug Administration for neonates with hypoxic respiratory failure, however, it is used off-label for acute respiratory distress syndrome, acute bronchiolitis, and COVID-19. PURPOSE: In this article we review the currently understood biological action and therapeutic uses of NO through nitric oxide donors such as inhaled nitric oxide. We will then explore recent studies describing use of NO in cardiopulmonary bypass and extracorporeal membrane oxygenation and speculate on NO's future uses.

The safe addition of nitric oxide to the sweep gas of the extracorporeal membrane oxygenation circuit in a pediatric cardiac intensive care unit.

Background: Nitric Oxide (NO) is a naturally occurring modulator of inflammation found in the human body. Several studies in the pediatric cardiothoracic surgery literature have demonstrated some beneficial clinical effects when NO is added to the sweep gas of the cardiopulmonary bypass circuit.Purpose: Our primary aim was to determine the safety of incorporating nitric oxide into the oxygenator sweep gas of the extracorporeal membrane oxygenation (ECMO) circuit. Secondarily, we looked at important clinical outcomes, such as survival, blood product utilization, and common complications related to ECMO.Methods: We performed a single center, retrospective review of all patients at our institution who received ECMO between January 1, 2017 and March 31, 2023. We began additing NO to the ECMO sweep gas in 2019. Results: There were no instances of clinically significant methemoglobinemia with the addition of NO to the sweep gas (0% vs 0%, p = 1). The median daily methemoglobin level was higher in those who received NO via the sweep gas when compared to those who did not (1.6 vs 1.1, p = <0.001). Conclusions: The addition of NO to the sweep gas of the ECMO circuit is safe.

Risk Factors for an Elevated Ventricular End-Diastolic Pressure Prior to the Fontan Operation.

Systemic ventricular end-diastolic pressure (SVEDP) is an important determinant of pulmonary artery pressure in those with a Fontan circulation. Predictors of an elevated SVEDP have been incompletely identified in this population. All who underwent the Fontan operation at our center between 1/2009 and 12/2013 were retrospectively identified. SVEDP at the pre-Fontan catheterization and other patient variables were extracted. We identified 61 patients. Pre-Fontan SVEDP was positively associated with systemic ventricular systolic pressure (ß = 0.4, p = 0.004), aortic systolic pressure (ß = 0.3, p = 0.007), aortic mean pressure (ß = 0.3, p = 0.02), and decreased ventricular systolic function (p = 0.03). Compared to those with pre-Fontan SVEDP ≤ 7 mmHg, patients with SVEDP > 7 mmHg had higher average ventricular systolic pressure (85.0 ± 7.5 vs. 78.7 ± 8.3 mmHg, p = 0.003), higher average descending aorta mean pressure (62.4 ± 4.9 vs. 58.6 ± 8.1 mmHg, p = 0.03), and a higher incidence of decreased ventricular systolic function (36 vs. 15%, p = 0.07). For those with a systemic right ventricle, the SVEDP decreased significantly from the pre-Stage 2 to pre-Fontan measurements (8.7 ± 2.6 vs. 7.3 ± 2.0 mmHg, p = 0.02), but not for those with a systemic left ventricle (7.8 ± 2.0 vs. 7.2 ± 1.8 mmHg, p = 0.3). At pre-Fontan catheterization, decreased ventricular systolic function and markers of systemic afterload were positively associated with the SVEDP. SVEDP decreased significantly after Stage 2 for those with a systemic right ventricle, but not for those with a systemic left ventricle; the systemic right ventricle may be particularly vulnerable to pre-Stage 2 volume loading.

Inhibition of Murine Pulmonary Microvascular Endothelial Cell Apoptosis Promotes Recovery of Barrier Function under Septic Conditions.

Sepsis is characterized by injury of the pulmonary microvasculature and the pulmonary microvascular endothelial cells (PMVEC), leading to barrier dysfunction and acute respiratory distress syndrome (ARDS). Our recent work identified a strong correlation between PMVEC apoptosis and microvascular leak in septic mice in vivo, but the specific role of apoptosis in septic PMVEC barrier dysfunction remains unclear. Thus, we hypothesize that PMVEC apoptosis is likely required for PMVEC barrier dysfunction under septic conditions in vitro. Septic stimulation (mixture of tumour necrosis factor α, interleukin 1ß, and interferon γ [cytomix]) of isolated murine PMVEC resulted in a significant loss of barrier function as early as 4 h after stimulation, which persisted until 24 h. PMVEC apoptosis, as reflected by caspase activation, DNA fragmentation, and loss of membrane polarity, was first apparent at 8 h after cytomix. Pretreatment of PMVEC with the pan-caspase inhibitor Q-VD significantly decreased septic PMVEC apoptosis and was associated with reestablishment of PMVEC barrier function at 16 and 24 h after stimulation but had no effect on septic PMVEC barrier dysfunction over the first 8 h. Collectively, our data suggest that early septic murine PMVEC barrier dysfunction driven by proinflammatory cytokines is not mediated through apoptosis, but PMVEC apoptosis contributes to late septic PMVEC barrier dysfunction.

Left Pulmonary Artery from the Ascending Aorta: A Case Report and Review of Published Cases.

The left pulmonary artery arising from the ascending aorta is an infrequent finding. It may be found isolated or with intracardiac anomalies. We present a new case of the left pulmonary artery arising from the ascending aorta and pool these findings with those of previously reported cases. Associated cardiac, extracardiac, and syndromic findings are discussed along with the implications of these in the evaluation and management of this condition.

Atrial fibrillation in adults with congenital heart disease following cardiac surgery in a single center: Analysis of incidence and risk factors.

OBJECTIVE: The primary aim of our work is to determine the incidence of atrial fibrillation following cardiac surgery in adults with congenital heart disease. Secondary aims include identifying risk factors predictive of developing early postoperative atrial fibrillation and morbidities associated with early postoperative atrial fibrillation. DESIGN: Retrospective analysis. SETTING: Single center, quaternary care children's hospital. PATIENTS: This review included patients at least 18 years of age with known congenital heart disease who underwent cardiac surgery requiring a median sternotomy at our congenital heart center from January 1, 2012 to December 31, 2016. INTERVENTIONS: None. OUTCOME MEASURES: The primary outcome was early postoperative atrial fibrillation. Secondary outcomes included preoperative comorbidities, preoperative echocardiographic findings, operative details, and postoperative morbidities, such length of stay, reintubation, stroke, and death. RESULTS: The incidence of early postoperative atrial fibrillation was 21%. Those who developed early postoperative atrial fibrillation were older (50 years vs 38 years, P =< .001), had a history of atrial fibrillation prior to surgery, had preoperative pulmonary hypertension, and had longer cardiopulmonary bypass times (103 minutes vs 84 minutes, P = .025) when compared to those who did not develop postoperative atrial fibrillation. Multivariate analysis identified age greater than 60, preoperative pulmonary hypertension, mitral valve intervention, and the need for postoperative inotropic support as being independent predictors of postoperative atrial fibrillation. Those who developed postoperative atrial fibrillation remained in the hospital longer (9 days vs 7 days, P =< .001). CONCLUSIONS: Atrial fibrillation is a common complication following cardiac surgery in adults with congenital heart disease. Age, preoperative comorbidities, type of surgical intervention, and the need for perioperative inotropic infusions may predict the risk of atrial fibrillation in this unique patient population.

Single-stage repair of double outlet right ventricle with subpulmonic ventricular septal defect (Taussig-Bing anomaly).

Double outlet right ventricle with subpulmonic ventricular septal defect is a very rare form of congenital heart disease. Surgical correction involves closure of the ventricular septal defect with baffling of blood flow from the left ventricle to the pulmonic valve and arterial switch of the usually side-by-side great arteries. In this tutorial, we present our surgical technique for single-stage repair of this complex anomaly.

Recurrent nonbacterial thrombotic endocarditis: A novel therapeutic approach.

We present the case of a 29-year-old male with a history of Mizuho hemolytic anemia, a rare form of unstable hemoglobinopathy, who presented with congestive heart failure secondary to recurrent valve thrombosis despite appropriate oral anticoagulation. He subsequently required mitral and aortic valve replacement. Pathologic examination revealed extensive nonbacterial thrombotic endocarditis. Due to recurrent thrombosis despite therapeutic anticoagulation, we elected to treat him with red blood cell exchange transfusions and hydroxyurea. He has remained free of symptoms for almost two years with this treatment regimen without side effects. .

A Pediatric Diabetic Ketoacidosis Management Protocol Incorporating a Two-Bag Intravenous Fluid System Decreases Duration of Intravenous Insulin Therapy.

OBJECTIVES: Diabetic ketoacidosis (DKA) is a leading cause of morbidity and mortality in children with type 1 diabetes. We implemented a standardized DKA management protocol by using a 2-bag intravenous (IV) fluid system. The purpose of the study was to examine if the protocol improved clinical outcomes and process efficiency. METHODS: This was a retrospective study of patients who did and did not undergo the protocol. Patients were included if they were 18 years of age or younger, were diagnosed with DKA, admitted to an intensive care unit or stepdown unit, and received continuous IV insulin. RESULTS: Of 119 encounters evaluated, 46 (38.7%) received treatment with the protocol and 73 (61.3%) did not. The median time to normalization of ketoacidosis was 9 hours (IQR 5-12) and 9 hours (IQR 6.5-13) for protocol and non-protocol groups, respectively (p = 0.14). The median duration of IV insulin therapy was 16.9 hours (IQR 13.7-21.5) vs. 21 hours (IQR 15.3-26) for protocol and non-protocol groups (p = 0.03). The median number of adjustments to insulin drip rate was 0 (IQR 0-1) and 2 (IQR 0-3) for protocol and non-protocol groups (p = 0.0001). There was no difference in the incidence of hypokalemia, hypoglycemia, or cerebral edema. CONCLUSIONS: The protocol did not change time to normalization of ketoacidosis but did decrease the duration of insulin therapy, number of adjustments to insulin drip rate, and number of wasted IV fluid bags without increasing the incidence of adverse events.

The role of TIMPs in regulation of extracellular matrix proteolysis.

Tissue inhibitors of metalloproteinases (TIMPs), which inhibit matrix metalloproteinases (MMPs) as well as the closely related, a disintegrin and metalloproteinases (ADAMs) and ADAMs with thrombospondin motifs (ADAMTSs), were traditionally thought to control extracellular matrix (ECM) proteolysis through direct inhibition of MMP-dependent ECM proteolysis. This classical role for TIMPs suggests that increased TIMP levels results in ECM accumulation (or fibrosis), whereas loss of TIMPs leads to enhanced matrix proteolysis. Mice lacking TIMP family members have provided support for such a role; however, studies with these TIMP deficient mice have also demonstrated that loss of TIMPs can often be associated with an accumulation of ECM. Collectively, these studies suggest that the divergent roles of TIMPs in matrix accumulation and proteolysis, which together can be referred to as ECM turnover, are dependent on the TIMP, specific tissue, and local tissue environment (i.e. health vs. injury/disease). Ultimately, these combined factors dictate the specific metalloproteinases being regulated by a given TIMP, and it is likely the diversity of metalloproteinases and their physiological substrates that determines whether TIMPs inhibit matrix proteolysis or accumulation. In this review, we discuss the evidence for the dichotomous roles of TIMPs in ECM turnover highlighting some of the common findings between different TIMP family members. Importantly, while we now have a better understanding of the role of TIMPs in regulating ECM turnover, much remains to be determined. Data on the specific metalloproteinases inhibited by different TIMPs in vivo remains limited and must be the focus of future studies.

A rare pediatric cardiac anomaly: Quadricuspid aortic valve with aortic regurgitation.

A quadricuspid aortic valve is rarely diagnosed in children, but it can be associated with significant aortic regurgitation. It is important for pediatric cardiologists to be aware of this pathologic entity. We present a nine-year-old male, diagnosed with a quadricuspid aortic valve and mild aortic regurgitation.