First experience with a paracorporeal artificial lung in a small child with pulmonary hypertension

Surgical considerations in infant lung transplantation: Challenges and opportunities

Lung transplantation is a crucial component in the treatment of end-stage lung disease in infants. Traditionally, most lung transplants have been performed in older children and adults, resulting in a scarcity of data for infant patients. To address the challenges unique to this age group, novel strategies to provide the best preoperative, intraoperative, and postoperative care for these youngest patients are paramount. We review recent advances in bridge-to-transplantation therapy, including the use of a paracorporeal lung assist device, and differences in surgical technique, including bronchial artery revascularization, for incorporation into the overarching treatment strategy for infants undergoing lung transplantation.

Low-Resistance, Concentric-Gated Pediatric Artificial Lung for End-Stage Lung Failure

Children with end-stage lung failure awaiting lung transplant would benefit from improvements in artificial lung technology allowing for wearable pulmonary support as a bridge-to-transplant therapy. In this work, we designed, fabricated, and tested the Pediatric MLung-a dual-inlet hollow fiber artificial lung based on concentric gating, which has a rated flow of 1 L/min, and a pressure drop of 25 mm Hg at rated flow. This device and future iterations of the current design are designed to relieve pulmonary arterial hypertension, provide pulmonary support, reduce ventilator-associated injury, and allow for more effective therapy of patients with end-stage lung disease, including bridge-to-transplant treatment.

Approach to pulmonary vascular disease in the ICU

PURPOSE OF REVIEW

Pulmonary vascular disease (PVD) complicates the course of many cardiovascular, pulmonary and other systemic diseases in children. The physiological sequelae (pulmonary hypertension and elevated pulmonary vascular resistance) can overwhelm the right ventricle and lead to circulatory collapse. Despite the common end-point, the preceding pathophysiology is complex and variable and requires a tailored approach to diagnosis and management. In this article, we will review the most recent evidence and explore an approach to current controversies in the diagnosis and management of common or challenging patient subgroups.

RECENT FINDINGS

New methods of interpreting data derived from echocardiography and cardiac magnetic resonance imaging may assist in risk stratification and response to therapy. In specific patient subgroups, standard pharmacological therapies to reduce right ventricle afterload may be overutilized, ineffective and in some cases harmful. In the patient failing pharmacological therapy, new and novel techniques are being explored including temporary extracorporeal mechanical circulatory support, pumpless lung assist devices and novel surgical and catheterization procedures.

SUMMARY

PVD is a diverse entity, and attention to the underlying pathophysiology is essential for appropriate management. Despite significant advances in our understanding, the majority of data comes from small uncontrolled studies and must be interpreted with caution.

Early in vivo experience with the pediatric continuous-flow total artificial heart

BACKGROUND

Heart transplantation in infants and children is an accepted therapy for end-stage heart failure, but donor organ availability is low and always uncertain. Mechanical circulatory support is another standard option, but there is a lack of intracorporeal devices due to size and functional range. The purpose of this study was to evaluate the in vivo performance of our initial prototype of a pediatric continuous-flow total artificial heart (P-CFTAH), comprising a dual pump with one motor and one rotating assembly, supported by a hydrodynamic bearing.

METHODS

In acute studies, the P-CFTAH was implanted in 4 lambs (average weight: 28.7 ± 2.3 kg) via a median sternotomy under cardiopulmonary bypass. Pulmonary and systemic pump performance parameters were recorded.

RESULTS

The experiments showed good anatomical fit and easy implantation, with an average aortic cross-clamp time of 98 ± 18 minutes. Baseline hemodynamics were stable in all 4 animals (pump speed: 3.4 ± 0.2 krpm; pump flow: 2.1 ± 0.9 liters/min; power: 3.0 ± 0.8 W; arterial pressure: 68 ± 10 mm Hg; left and right atrial pressures: 6 ± 1 mm Hg, for both). Any differences between left and right atrial pressures were maintained within the intended limit of ±5 mm Hg over a wide range of ratios of systemic-to-pulmonary vascular resistance (0.7 to 12), with and without pump-speed modulation. Pump-speed modulation was successfully performed to create arterial pulsation.

CONCLUSION

This initial P-CFTAH prototype met the proposed requirements for self-regulation, performance, and pulse modulation.

Paracorporeal Lung Devices: Thinking Outside the Box

Extracorporeal Membrane Oxygenation (ECMO) is a resource intensive, life-preserving support system that has seen ever-expanding clinical indications as technology and collective experience has matured. Clinicians caring for patients who develop pulmonary failure secondary to cardiac failure can find themselves in unique situations where traditional ECMO may not be the ideal clinical solution. Existing paracorporeal ventricular assist device (VAD) technology or unique patient physiologies offer the opportunity for thinking "outside the box." Hybrid ECMO approaches include splicing oxygenators into paracorporeal VAD systems and alternative cannulation strategies to provide a staged approach to transition a patient from ECMO to a VAD. Alternative technologies include the adaptation of ECMO and extracorporeal CO₂ removal systems for specific physiologies and pediatric aged patients. This chapter will focus on: (1) hybrid and alternative approaches to extracorporeal support for pulmonary failure, (2) patient selection and, (3) technical considerations of these therapies. By examining the successes and challenges of the relatively select patients treated with these approaches, we hope to spur appropriate research and development to expand the clinical armamentarium of extracorporeal technology.

Adverse Outcomes in Neonates and Children with Pulmonary Artery Hypertension Supported with ECMO

Extracorporeal membrane oxygenation (ECMO) has been increasingly used to rescue neonates and children with cardiac or respiratory failure, and critical illnesses including pulmonary artery hypertension (PAH) unresponsive to conventional therapies. This study assesses mortality and outcomes in neonates and children with PAH supported with ECMO. Neonates and children from the 2012 Health Care Cost and Use Project Kids' Database were identified using ICD-9 codes. Children with congenital heart disease were excluded. Univariate logistic regression was applied to assess the relationship between ECMO and outcomes using matched cohorts for age, elective admission, and Elixhauser comorbidity score. We identified 9,355 neonates and children with PAH (0.15%). The incidence of ECMO was 1.4% (132/9,355). After propensity-matched analysis, 130 neonates and children were included in each group. The incidence of mortality was 39% in the group supported with ECMO and 8% in the control group (odds ratio [OR]: 6.98, 95% confidence interval [CI]: 3.43-14.21, p < 0.001). Neonates and children on ECMO had higher odds for acute kidney injury (OR: 2.41, 95% CI: 1.30-4.47, p = 0.005), neurologic complications (OR: 7.11, 95% CI: 1.57-32.18, p = 0.011), sepsis (OR: 2.69, 95% CI: 1.46-4.96, p = 0.002), and thrombotic complications (OR: 2.90, 95% CI: 1.10-7.67, p = 0.032). Neonates and children with PAH supported with ECMO have higher mortality rate and complications compared with matched controls with PAH.

Pediatric Artificial Lung: A Low-Resistance Pumpless Artificial Lung Alleviates an Acute Lamb Model of Increased Right Ventricle Afterload

Lung disease in children often results in pulmonary hypertension and right heart failure. The availability of a pediatric artificial lung (PAL) would open new approaches to the management of these conditions by bridging to recovery in acute disease or transplantation in chronic disease. This study investigates the efficacy of a novel PAL in alleviating an animal model of pulmonary hypertension and increased right ventricle afterload. Five juvenile lambs (20-30 kg) underwent PAL implantation in a pulmonary artery to left atrium configuration. Induction of disease involved temporary, reversible occlusion of the right main pulmonary artery. Hemodynamics, pulmonary vascular input impedance, and right ventricle efficiency were measured under 1) baseline, 2) disease, and 3) disease + PAL conditions. The disease model altered hemodynamics variables in a manner consistent with pulmonary hypertension. Subsequent PAL attachment improved pulmonary artery pressure (p = 0.018), cardiac output (p = 0.050), pulmonary vascular input impedance (Z.0 p = 0.028; Z.1 p = 0.058), and right ventricle efficiency (p = 0.001). The PAL averaged resistance of 2.3 ± 0.8 mm Hg/L/min and blood flow of 1.3 ± 0.6 L/min. This novel low-resistance PAL can alleviate pulmonary hypertension in an acute animal model and demonstrates potential for use as a bridge to lung recovery or transplantation in pediatric patients with significant pulmonary hypertension refractory to medical therapies.

Anesthesia for Placement of a Paracorporeal Lung Assist Device and Subsequent Heart-Lung Transplantation in a Child with Suprasystemic Pulmonary Hypertension and End-Stage Respiratory Failure

Pediatric patients with end-stage respiratory failure and pulmonary hypertension traditionally have poor outcomes when bridged with extracorporeal membrane oxygenation to lung or heart-lung transplantation. Therefore, several institutions have attempted paracorporeal lung assist devices as a bridge. However, given the small number of patients, little is known about approaches to anesthetic induction in these hemodynamically unstable patients either before placement of a device or anesthetic induction once a device is in situ. In this case report, we describe our anesthetic experience managing a 13-year-old boy for both paracorporeal lung assist device placement and subsequent heart-lung transplantation.

Recommendations for utilization of the paracorporeal lung assist device in neonates and young children with pulmonary hypertension

The management of decompensating critically ill children with severe PH is extremely challenging and requires a multidisciplinary approach. Unfortunately, even with optimal care, these children might continue to deteriorate and develop inadequate systemic perfusion and at times cardiac arrest secondary to a pulmonary hypertensive crisis. Tools to support these children are limited, and at times, the team should proceed with offering extracorporeal support, especially in newly diagnosed patients who have not benefitted from medical therapy prior to their acute deterioration, in patients with severe pulmonary venous disease and in patients with alveolar capillary dysplasia. Currently, the only approved mode for extracorporeal support in pediatric patients with PH eligible for lung transplantation is ECMO. To decrease the risks associated with ECMO, and offer potential for increased duration of support, extubation, and rehabilitation, we transitioned four small children with refractory PH from ECMO to a device comprising an oxygenator interposed between the PA and LA. This work describes in great detail our experience with this mode of support with emphasis on exclusion criteria, the implantation procedure, and the post-implantation management.

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

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

Successful Semi-Ambulatory Veno-Arterial Extracorporeal Membrane Oxygenation Bridge to Heart-Lung Transplantation in a Very Small Child

Lung transplantation (LTx) may be denied for children on extracorporeal membrane oxygenation (ECMO) due to high risk of cerebral hemorrhage. Rarely has successful LTx been reported in children over 10 years of age receiving awake or ambulatory veno-venous ECMO. LTx following support with ambulatory veno-arterial ECMO (VA ECMO) in children has never been reported to our knowledge. We present the case of a 4-year-old, 12-kg child with heritable pulmonary artery hypertension and refractory right ventricular failure. She was successfully bridged to heart-lung transplantation (HLTx) using ambulatory VA ECMO. Initial resuscitation with standard VA ECMO was converted to an ambulatory circuit using Berlin heart cannulae. She was extubated and ambulating around her bed while on VA ECMO for 40 days. She received an HLTx from an oversized marginal lung donor. Despite a cardiac arrest and Grade 3 primary graft dysfunction, she made a full recovery without neurological deficits. She achieved 104% force expiratory volume in 1 s 33 months post-HLTx. Ambulatory VA ECMO may be a useful strategy to bridge very young children to LTx or HLTx. Patient tailored ECMO cannulation, minimization of hemorrhage, and thrombosis risks while on ECMO contributed to a successful HLTx in our patient.

Trends in pediatric pulmonary hypertension-related hospitalizations in the United States from 2000-2009

There are few data on the epidemiology of pulmonary hypertension (PH)-related hospitalizations in children in the United States. Our aim was to determine hospital mortality, length of hospitalization, and hospital charges pertaining to PH-related hospitalizations and also the effects of codiagnoses and comorbidities. A retrospective review of the Kids' Inpatient Database during the years 2000, 2003, 2006, and 2009 was analyzed for patients ≤20 years of age with a diagnosis of PH by ICD-9 (International Classification of Diseases, Ninth Revision) codes, along with associated diagnoses and comorbidities. Descriptive statistics, including Rao-Scott χ(2), ANOVA, and logistic regression models, were utilized on weighted values with survey analysis procedures. The number of PH-related hospital admissions is rising, from an estimated 7,331 (95% confidence interval [CI]: 5,556-9,106) in 2000 to 10,792 (95% CI: 8,568-13,016) in 2009. While infant age and congenital heart disease were most commonly associated with PH-related hospitalizations, they were not associated with mortality. Overall mortality for PH-related hospitalizations was greater than that for hospitalizations not associated with PH, 5.7% versus 0.4% (odds ratio: 16.22 [95% CI: 14.78%-17.8%], P < 0.001), but mortality is decreasing over time. Sepsis, respiratory failure, acute renal failure, hepatic insufficiency, arrhythmias, and the use of extracorporeal membrane oxygenation are associated with mortality. The number of PH-related hospitalizations is increasing in the United States. The demographics of PH in this study are evolving. Despite the increasing prevalence, mortality is improving.

Extracorporeal support in children with pediatric acute respiratory distress syndrome: proceedings from the Pediatric Acute Lung Injury Consensus Conference

OBJECTIVE

Extracorporeal life support has undergone a revolution in the past several years with the advent of new, miniaturized equipment and success in supporting patients with a variety of illnesses. Most experience has come with the use of extracorporeal membrane oxygenation, a modified form of cardiopulmonary bypass that can support the heart, lungs, and circulation for days to months at a time. To describe the recommendations for the use of extracorporeal membrane oxygenation in children with pediatric acute respiratory distress syndrome based on a review of the literature and expert opinion.

DESIGN

Consensus conference of experts in pediatric acute lung injury.

METHODS

A panel of 27 experts met over the course of 2 years to develop a taxonomy to define pediatric acute respiratory distress syndrome and to make recommendations regarding treatment and research priorities. The extracorporeal support subgroup comprised two international experts. When published data were lacking, a modified Delphi approach emphasizing strong professional agreement was used.

RESULTS

The Pediatric Acute Lung Injury Consensus Conference experts developed and voted on a total of 151 recommendations addressing the topics related to pediatric acute respiratory distress syndrome, 11 of which related to extracorporeal support. All recommendations had agreement, with 10 recommendations (91%) achieving strong agreement. These recommendations included the utilization of extracorporeal support for reversible causes of pediatric acute respiratory distress syndrome, consideration of quality of life when making the decision to use extracorporeal support, and the use of the Extracorporeal Life Support Organization registry to report all extracorporeal support activity, among others.

CONCLUSIONS

Pediatric extracorporeal membrane oxygenation for pediatric acute respiratory distress syndrome could benefit from more specific data collection and collaboration of focused investigators to establish validated criteria for optimal application of extracorporeal membrane oxygenation and patient management protocols. Until that time, consensus opinion offers some insight into guidelines.

Paracorporeal lung assist devices as a bridge to recovery or lung transplantation in neonates and young children

OBJECTIVE

To evaluate paracorporeal lung assist devices to treat neonates and children with decompensated respiratory failure as a bridge to recovery or lung transplantation.

METHODS

One neonate (23 days old) and 3 young children (aged 2, 9, and 23 months) presented with primary lung disease with pulmonary hypertension, including alveolar capillary dysplasia in 2 and right pulmonary hypoplasia and primary pulmonary hypertension in 1. The patients were listed for lung transplantation but decompensated and required extracorporeal membrane oxygenation (ECMO). The patients were transitioned from ECMO to a pumpless paracorporeal lung assist device (Maquet Quadrox-iD oxygenator in 3, Novalung in 1) with inflow from the pulmonary artery and return to the left atrium.

RESULTS

The patients were weaned from ECMO and supported by the device for 44 ± 29 days (range, 5-74). Three patients were extubated while supported by the device (after 9, 15, and 72 days). One patient was bridged to lung transplant (9 months old, with alveolar capillary dysplasia, supported 5 days). One patient was bridged to recovery with maximal medical therapy (23 months old, with primary pulmonary hypertension, supported 23 days). Two patients died while awaiting a suitable lung donor after a support time of 54 and 72 days.

CONCLUSIONS

Pediatric patients bridged from ECMO to lung transplantation have poor results. An alternative method for longer term respiratory support was necessary as a bridge for these patients. The use of a paracorporeal lung assist device successfully supported 4 patients to recovery, lung transplantation, or past the average wait time for pediatric donor lungs (27 days). This therapy has the potential to bridge children with decompensated respiratory failure to lung transplantation.

Pediatric extracorporeal life support in specialized situations

OBJECTIVES

The purpose of this review was to provide a systematic review of the literature regarding the use of extracorporeal life support (ECLS) in various specialized conditions, as part of the Pediatric Cardiac Intensive Care Society/Extracorporeal Life Support Organization Joint Statement on Mechanical Circulatory Support.

DATA SOURCES

MEDLINE and PubMed.

STUDY SELECTION

Searches for published abstracts and articles were conducted using the following MeSH terms: extracorporeal life support, extracorporeal membrane oxygenation, or mechanical support, and pediatric or children.

DATA EXTRACTION

Abstracts of all articles including case reports were reviewed; the full article was reviewed if the abstract indicated that it focused on extracorporeal life support for conditions other than primary respiratory disease or persistent pulmonary hypertension of the newborn and described outcomes such as survival to hospital discharge. Studies with potential overlapping patients were highlighted in the review process and summary results.

DATA SYNTHESIS

Classification of recommendations and level of evidence are expressed in the American College of Cardiology Foundation/American Heart Association format.

CONCLUSIONS

The majority of specialized situations where extracorporeal life support is used fall into the category of class II-III evidence. Class I indications for extracorporeal life support in the pediatric population include myocarditis and in the context of acute interventions in the cardiac catheterization laboratory.

Use of a low-resistance compliant thoracic artificial lung in the pulmonary artery to pulmonary artery configuration

BACKGROUND

Thoracic artificial lungs have been proposed as a bridge to transplant in patients with end-stage lung disease. Systemic embolic complications can occur after thoracic artificial lung attachment in the pulmonary artery to left atrium configuration. Therefore, we evaluated the function of a compliant thoracic artificial lung attached via the proximal pulmonary artery to distal main pulmonary artery configuration.

METHODS

The compliant thoracic artificial lung was attached to 5 sheep (63 ± 0.9 kg) in the proximal pulmonary artery to distal main pulmonary artery configuration. Device function and animal hemodynamics were assessed at baseline and with approximately 60%, 75%, and 90% of cardiac output diverted to the compliant thoracic artificial lung. At each condition, dobutamine (0 and 5 μg·kg(-1)·min(-1)) was used to simulate rest and exercise conditions.

RESULTS

At rest, cardiac output decreased from 6.20 ± 0.53 L/min at baseline to 5.40 ± 0.43, 4.66 ± 0.31, and 4.05 ± 0.27 L/min with 60%, 75%, and 90% of cardiac output to the compliant thoracic artificial lung, respectively (P < .01 for each flow diversion vs baseline). During exercise, cardiac output decreased from 7.85 ± 0.70 L/min at baseline to 7.46 ± 0.55, 6.93 ± 0.51, and 5.96 ± 0.44 L/min (P = .82, P = .19, and P < .01 with respect to baseline) with 60%, 75%, and 90% of cardiac output to the compliant thoracic artificial lung, respectively. The artificial lung resistance averaged 0.46 ± 0.02 and did not vary significantly with blood flow rate.

CONCLUSIONS

Use of a compliant thoracic artificial lung may be feasible in the proximal pulmonary artery to distal main pulmonary artery setting if its blood flow is held at less than 75% of cardiac output. To ensure a decrease in cardiac output of less than 10%, a blood flow rate less than 60% of cardiac output is advised.

Extracorporeal life support: an update of Rogers' Textbook of Pediatric Intensive Care

INTRODUCTION

The field of extracorporeal life support, which has focused predominantly on extracorporeal membrane oxygenation in the past, is undergoing rapid expansion following years of stagnation as newer devices and improved technology have become available. Additionally, new cannulae and cannulation techniques have allowed extracorporeal life support to be expanded to many groups who would have been excluded from support in the past.

REVIEW

This update will review the current state of the art since Rogers' Textbook of Pediatric Intensive Care (Fourth Edition) was published several years ago. The changing environment of extracorporeal support in terms of patient populations, technological advances, patient management, and outcome will be discussed.

CONCLUSIONS

Continued examination of the criteria and circumstances where extracorporeal life support is applied as well as outcomes which include morbidity, cost effectiveness, and quality of life are needed areas of continued research. Increasing collaborations between all centers performing extracorporeal life support throughout the world should remain a priority to further research and understanding of this complex field.