Extracorporeal membrane oxygenation as a bridge to lung transplantation

Intraoperative Circulatory Support in Lung Transplantation: Current Trend and Its Evidence

Lung transplantation has a high risk of haemodynamic complications in a highly vulnerable patient population. The effects on the cardiovascular system of the various underlying end-stage lung diseases also contribute to this risk. Following a literature review and based on our own experience, this review article summarises the current trends and their evidence for intraoperative circulatory support in lung transplantation. Identifiable and partly modifiable risk factors are mentioned and corresponding strategies for treatment are discussed. The approach of first identifying risk factors and then developing an adjusted strategy is presented as the ERSAS (early risk stratification and strategy) concept. Typical haemodynamic complications discussed here include right ventricular failure, diastolic dysfunction caused by left ventricular deconditioning, and reperfusion injury to the transplanted lung. Pre- and intra-operatively detectable risk factors for the occurrence of haemodynamic complications are rare, and the therapeutic strategies applied differ considerably between centres. However, all the mentioned risk factors and treatment strategies can be integrated into clinical treatment algorithms and can influence patient outcome in terms of both mortality and morbidity.

Extracorporeal membrane oxygenation in lung transplantation: Indications, techniques and results

The use of extracorporeal membrane oxygenation (ECMO) in the field of lung transplantation has rapidly expanded over the past 30 years. It has become an important tool in an increasing number of specialized centers as a bridge to transplantation and in the intra-operative and/or post-operative setting. ECMO is an extremely versatile tool in the field of lung transplantation as it can be used and adapted in different configurations with several potential cannulation sites according to the specific need of the recipient. For example, patients who need to be bridged to lung transplantation often have hypercapnic respiratory failure that may preferably benefit from veno-venous (VV) ECMO or peripheral veno-arterial (VA) ECMO in the case of hemodynamic instability. Moreover, in an intra-operative setting, VV ECMO can be maintained or switched to a VA ECMO. The routine use of intra-operative ECMO and its eventual prolongation in the post-operative period has been widely investigated in recent years by several important lung transplantation centers in order to assess the graft function and its potential protective role on primary graft dysfunction and on ischemia-reperfusion injury. This review will assess the current evidence on the role of ECMO in the different phases of lung transplantation, while analyzing different studies on pre, intra- and post-operative utilization of this extracorporeal support.

Extracorporeal Membrane Oxygenation as a Bridge to Lung Transplant

Extracorporeal membrane oxygenation (ECMO) is a cardiopulmonary technology capable of supporting cardiac and respiratory function in the presence of end-stage lung disease. Initial experiences using ECMO as a bridge to lung transplant (ECMO-BTLT) were characterized by high rates of ECMO-associated complications and poor posttransplant outcomes. More recently, ECMO-BTLT has garnered success in preserving patients' physiologic condition and candidacy prior to lung transplant due to technological advances and improved management. Despite recent growth, clinical practice surrounding use of ECMO-BTLT remains variable, with little data to inform optimal patient selection and management. Although many questions remain, the use of ECMO-BTLT has shown promising outcomes suggesting that ECMO-BTLT can be an effective strategy to ensure that complex and rapidly decompensating patients with end-stage lung disease can be safely transplanted with good outcomes. Further studies are needed to refine and inform practice patterns, management, and lung allocation in this high-risk and fragile patient population.

Bridging to Lung Transplantation

Lung transplantation is the gold standard for treating patients with end-stage lung disease. Such patients can present with severe illness on the waitlist and may deteriorate before a lung donor is available. Bridging strategies with extracorporeal membrane oxygenation (ECMO) are valuable for getting patients to transplant and provide a chance at survival. The current article describes the indications, contraindications, and techniques involved in bridging to lung transplantation with ECMO.

Extracorporeal support, during and after lung transplantation: the history of an idea

During recent years, continuous technological innovation has provoked an increase of extracorporeal life support (ECLS) use for perioperative cardiopulmonary support in lung transplantation. Initial results were disappointing, due to ECLS-specific complications and high surgical risk of the supported patients. However, the combination of improved patient management, multidisciplinary team work and standardization of ECLS protocols has recently yielded excellent results in several case series from high-volume transplant centres. Therein, it was demonstrated that, although the prevalence of complications remains higher in supported patients, there may be no difference in long-term graft function between supported and non-supported patients. These results are important, because most of the patients who require ECLS support in lung transplantation are young and have no other chance to survive, but to be transplanted. Moreover, there is no device for "bridging to destination" therapy in lung transplantation. Of note, the evidence in favour of ECLS support in lung transplantation was never validated by randomized controlled trials, but by everyday experience at the patient bed-side. Here, we review the state-of-the-art ECLS evidence for intraoperative and postoperative cardiopulmonary support in lung transplantation.

Extracorporeal Membrane Oxygenation (Ecmo): Extended Indications for Artificial Support of Both Heart and Lungs

Extracorporeal membrane oxygenation (ECMO) was used to achieve temporary artificial support in cardiac and pulmonary function in 22 patients from 1987 to September 1990. Standard indications were postcardiotomy cardiogenic shock (n=4), neonatal (n=1) and adult respiratory distress syndrome (n=4). ECMO was also used for extended indications, such as graft failure following heart (n=11) or lung transplantation (n=2). In six of these cases ECMO was instituted as a bridge device to subsequent retransplantation of either the heart (n=4) or one lung (n=2). One out of nine patients supported by ECMO for standard indications, and two out of 13 patients supported for extended indications are long-term survivors. This series illustrates the results with ECMO in emergency situations, in patients under immunosuppressive protocols, or in patients with advanced lung failure requiring almost complete artificial gas exchange. In such complex situations, ECMO does provide stabilization until additional therapeutic measures are in effect. ECMO cannot be recommended for postoperative cardiogenic shock but short-term ECMO support is an accepted method in most cases with graft failure or pulmonary failure or other origin.

Principi e indicazioni dell’assistenza circolatoria e respiratoria extracorporea in chirurgia toracica

In origine, l’extracorporeal membrane oxygenation (ECMO) era una tecnica di assistenza respiratoria che utilizzava uno scambiatore gassoso a membrana. Per estensione, l’ECMO è diventata una tecnica respiratoria e cardiopolmonare utilizzata in caso di deficit respiratorio e/o cardiaco nell’attesa della restaurazione della funzione deficitaria o di un eventuale trapianto. Il supporto emodinamico può essere parziale o totale. Gli accessi vascolari possono essere periferici o centrali. Questo tipo di assistenza utilizza il concetto di circolazione extracorporea (CEC) sanguigna che in epoca moderna si è estesa con l’utilizzo di polmoni artificiali a membrana. Il circuito di base è semplice e comprende una pompa, un ossigenatore (che permette al sangue di caricarsi di O₂ e di eliminare CO₂) e delle vie d’accesso (una di drenaggio e una di reinfusione). La sua attuazione è facile, veloce e può essere avviata al letto del malato. Il miglioramento delle attrezzature, una migliore conoscenza delle tecniche e delle indicazioni, e le politiche di salute pubblica hanno reso popolare questa tecnica. Alcuni centri di chirurgia toracica la utilizzano di routine come assistenza alla realizzazione di un intervento terapeutico (soprattutto trapianto) assieme a team di rianimazione per il trattamento della sindrome da distress respiratorio acuto. Nel quadro della malattia polmonare dell’adulto, l’idea principale è quella di sviluppare il concetto di strategia minimalista con l’uso di una CEC adiuvante parziale – più che sostitutiva totale – che permetterebbe il recupero metabolico ad integrum del paziente. Nei prossimi anni, i progressi della tecnologia e dell’ingegneria così come le conoscenze approfondite permetteranno il miglioramento della prognosi dei pazienti colpiti da deficit respiratorio sotto assistenza meccanica.

Extracorporeal Lung Support as a Bridge to Diagnosis of Pulmonary Tumor Embolism

Bridging to diagnosis is an emerging technique used in end-stage cardiorespiratory failure that prolongs a patient's life using various modalities of extracorporeal lung support (ECLS) to achieve antemortem diagnosis. Pulmonary tumor embolism occurs when cell clusters travel from primary malignancies through venous circulation to the lungs, causing respiratory failure through inflammatory and venoocclusive pathways. Due to its nonspecific symptomatology, pulmonary tumor embolism remains an elusive diagnosis antemortem. Herein, we bridge a patient who presented in acute respiratory failure to the diagnosis of pulmonary tumor embolism from a gastric signet-ring cell carcinoma using ECLS modalities including venoarterial extracorporeal membrane oxygenation and centrally cannulated Novalung pumpless extracorporeal lung assist. We demonstrate the utility of this approach in diagnostically uncertain cases in unstable patients who are potentially acceptable ECLS and transplant candidates.

Principi e indicazioni dell’assistenza circolatoria e respiratoria extracorporea in chirurgia toracica

In origine, l’extracorporeal membrane oxygenation (ECMO) era una tecnica di assistenza respiratoria che utilizzava uno scambiatore gassoso a membrana. Per estensione, l’ECMO è diventata una tecnica respiratoria e cardiopolmonare utilizzata in caso di deficit respiratorio e/o cardiaco nell’attesa della restaurazione della funzione deficitaria o di un eventuale trapianto. Il supporto emodinamico può essere parziale o totale. Gli accessi vascolari possono essere periferici o centrali. Questo tipo di assistenza utilizza il concetto di circolazione extracorporea (CEC) sanguigna che in epoca moderna si è estesa con l’utilizzo di polmoni artificiali a membrana. Il circuito di base è semplice e comprende una pompa, un ossigenatore (che permette al sangue di caricarsi di O₂ e di eliminare CO₂) e delle vie d’accesso (una di drenaggio e una di reinfusione). La sua attuazione è facile, veloce e può essere avviata al letto del malato. Il miglioramento delle attrezzature, una migliore conoscenza delle tecniche e delle indicazioni, e le politiche di salute pubblica hanno reso popolare questa tecnica. Alcuni centri di chirurgia toracica la utilizzano di routine come assistenza alla realizzazione di un intervento terapeutico (soprattutto trapianto) assieme a team di rianimazione per il trattamento della sindrome da distress respiratorio acuto. Nel quadro della malattia polmonare dell’adulto, l’idea principale è quella di sviluppare il concetto di strategia minimalista con l’uso di una CEC adiuvante parziale – più che sostitutiva totale – che permetterebbe il recupero metabolico ad integrum del paziente. Nei prossimi anni, i progressi della tecnologia e dell’ingegneria così come le conoscenze approfondite permetteranno il miglioramento della prognosi dei pazienti colpiti da deficit respiratorio sotto assistenza meccanica.

Examining Noncardiac Surgical Procedures in Patients on Extracorporeal Membrane Oxygenation

As extracorporeal membrane oxygenation (ECMO) is increasingly used for patients with cardiac and/or pulmonary failure, the need for noncardiac surgical procedures (NCSPs) in these patients will continue to increase. This study examined the NCSP required in patients supported with ECMO and determined which variables affect outcomes. The National Inpatient Sample Database was examined for patients supported with ECMO from 2007 to 2010. There were 563 patients requiring ECMO during the study period. Of these, 269 (47.8%) required 380 NCSPs. There were 149 (39.2%) general surgical procedures, with abdominal exploration/bowel resection (18.2%) being most common. Vascular (29.5%) and thoracic procedures (23.4%) were also common. Patients requiring NCSP had longer median length of stay (15.5 vs. 9.2 days, p = 0.001), more wound infections (7.4% vs. 3.7%, p = 0.02), and more bleeding complications (27.9% vs. 17.3%, p = 0.01). The incidences of other complications and inpatient mortality (54.3% vs. 58.2%, p = 0.54) were similar. On logistic regression, the requirement of NCSPs was not associated with mortality (odds ratio [OR]: 0.91, 95% confidence interval [CI]: 0.68-1.23, p = 0.17). However, requirement of blood transfusion was associated with mortality (OR: 1.70, 95% CI: 1.06-2.74, p = 0.03). Although NCSPs in patients supported with ECMO does not increase mortality, it results in increased morbidity and longer hospital stay.

Canada's longest experience with extracorporeal membrane oxygenation as a bridge to lung transplantation: a case report

INTRODUCTION

Extracorporeal membrane oxygenation (ECMO) is a method of enabling gas exchange through an external membrane used to treat respiratory failure in critically ill patients. ECMO as a bridge to lung transplantation has been investigated as a potential method of reducing lung transplantation waitlist mortality. Herein we describe a case of ECMO as a bridge-to-lung transplantation for the duration of 35 days, which is the longest documented length of ECMO support before successful transplantation in Canada.

CASE DESCRIPTION

The prospective recipient was a 28-year-old female suffering from stage 4 pulmonary sarcoidosis. Given an acute exacerbation of her chronic respiratory failure, ECMO had to be initiated. She remained on ECMO for 35 days until a suitable set of donor lungs became available. The recipient had a prolonged course in hospital but was successfully discharged home where she continues to have good lung function. She remains alive and well at home 5 months post-transplantation and continues to improve and gain strength.

CONCLUSION

Our case provides hope that in the future we may be able to expand the population of recipients who may be candidates for lung transplantation. This case adds to the growing literature on the role of ECMO as a bridge-to-lung transplantation with the potential to reduce patient deaths while wait-listed for lung transplantation as well as increase the number of transplantations being performed.

Extracorporeal Membrane Oxygenation Applications in Cardiac Critical Care

The use of extracorporeal membrane oxygenation therapy (ECMO) in cardiac critical care has steadily increased over the past decade. Significant improvements in the technology associated with ECMO have propagated this recent resurgence and contributed to improved patient outcomes in the fields of cardiac and transplant (heart and lung) surgery. Specifically, ECMO is being increasingly utilized as a bridge to heart and lung transplantation, as well as to ventricular assist device placement. ECMO is also employed during the administration of cardiopulmonary resuscitation, known as extracorporeal life support. In this review, we examine the recent literature regarding the applications of ECMO and also describe emerging topics involving current ECMO management strategies.

Ambulatory extracorporeal membrane oxygenation as a bridge to lung transplantation: walking while waiting

The proportion of critically ill patients awaiting lung transplantation has increased since the implementation of the Lung Allocation Score (LAS) in 2005. Critically ill patients comprise a sizable proportion of wait-list mortality and are known to experience increased posttransplant complications. These critically ill patients have been successfully bridged to lung transplantation with extracorporeal membrane oxygenation (ECMO), but historically these patients have required excessive sedation, been immobile, and have had difficult functional recovery in the posttransplant period and high mortality. One solution to the deconditioning often seen in critically ill patients is the implementation of rehabilitation and ambulation while awaiting transplantation on ECMO. Ambulatory ECMO programs of this nature have been developed in an attempt to provide rehabilitation, physical therapy, and minimization of sedation prior to lung transplantation to improve both surgical and posttransplant outcomes. Favorable outcomes have been reported using this novel approach, but how and where this strategy should be implemented remain unclear. In this commentary, we review the currently available literature for ambulation and rehabilitation during ECMO support as a bridge to lung transplantation, discuss future directions for this technology, and address the important issues of resource allocation and regionalization of care as they relate to ambulatory ECMO.

Impact of extracorporeal membrane oxygenation or mechanical ventilation as bridge to combined heart-lung transplantation on short-term and long-term survival

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) and mechanical ventilation (MV) can be used as a bridge to heart-lung transplantation (HLT). The goal of this study was to determine if pretransplantation ECMO or MV affects survival in HLT.

METHODS

The United Network for Organ Sharing database was reviewed for all adult patients receiving HLT from 1995 to 2011. The primary outcome measured was risk-adjusted all cause mortality.

RESULTS

There were 542 adult patients received HLT during the study period. Of these, 15 (2.8%) required ECMO and 22 (4.1%) required MV as a bridge to transplantation. The groups were evenly matched with regards to recipient age, recipient gender, ischemic time, donor age, and donor gender. The ECMO cohort had worse survival than the control group at 30 days (20.0% vs. 83.5%) and 5 years (20.0% vs. 47.4%; P<0.001). When compared with control, patients requiring MV had worse survival at 1 month (77.3% vs. 83.5%) and 5 years (26.5% vs. 47.4%; P<0.001). The use of ECMO (hazard ratio [HR]=3.820, 95% confidence interval [CI]=1.600-9.116; P=0.003) or MV (HR=2.011, 95% CI=1.069-3.784; P=0.030) as a bridge to transplantation was independently associated with mortality on multivariate analysis. Recipient female gender was associated with survival (HR=0.754, 95% CI=0.570-0.998; P=0.048).

CONCLUSIONS

HLT recipients bridged by MV or ECMO have increased short-term and long-term mortality. Further studies are needed to optimize survival in these high-risk patients.

The evolution of extracorporeal life support as a bridge to lung transplantation

The use of extracorporeal membrane oxygenation (ECMO) as a bridge to lung transplantation was reported for the first time more than three decades ago; nevertheless, its use in lung transplantation was largely abandoned because of poor patient survival and frequent complications. The outcomes of patients bridged to lung transplantation using ECMO have substantially improved in the last 5 years. Recent advances in extracorporeal life support technology now allow patients with end-stage lung disease to be successfully supported for prolonged periods of time, preventing the use of mechanical ventilation and facilitating physical rehabilitation and ambulation while the patients awaits lung transplantation. This review briefly describes the evolution of ECMO use in lung transplantation and summarizes the available technology and current approaches to provide ECMO support.

Primary lung transplantation after bridge with extracorporeal membrane oxygenation: a plea for a shift in our paradigms for indications

BACKGROUND

The introduction of the lung allocation score has brought lung transplantation (LTX) of patients on extracorporeal membrane oxygenation (ECMO) bridge into the focus of interest. We reviewed our institutional experience with ECMO as a bridge to LTX.

METHODS

Between 1998 and 2011, 38 patients (median age 30.1 years, range 13-66 years) underwent ECMO support with intention to bridge to primary LTX. The underlying diagnosis was cystic fibrosis (n=17), pulmonary hypertension (n=4), idiopathic pulmonary fibrosis (n=9), adult respiratory distress syndrome (n=4), hemosiderosis (n=1), bronchiolitis obliterans (n=1), sarcoidosis (n=1), and bronchiectasis (n=1). The type of extracorporeal bridge was venovenous (n=18), venoarterial (n=15), interventional lung assist (n=1), or a stepwise combination of them (n=4). The median bridging time was 5.5 days (range 1-63) days. The type of transplantation was double LTX (n=7), size-reduced double LTX (n=8), lobar LTX (n=16), split LTX (n=2), and lobar LTX after ex vivo lung perfusion (n=1).

RESULTS

Four patients died before transplantation. Thirty-four patients underwent LTX, of them eight patients died in the hospital after a median stay of 24.5 days (range 1-180 days). Twenty-six patients left the hospital and returned to normal life (median hospital stay=47.5 days; range 21-90 days). The 1-, 3-, and 5-year survival for all transplanted patients was 60%, 60%, and 48%, respectively. The 1-, 3-, and 5-year survival conditional on 3-month survival for patients bridged with ECMO to LTX (78%, 78%, and 63%) was not worse than for other LTX patients within the same period of time (90%, 80%, and 72%, respectively, P=0.09, 0.505, and 0.344).

CONCLUSION

Transplantation of patients bridged on ECMO to LTX is feasible and results in acceptable outcome.

Extracorporeal membrane oxygenation as a bridge to lung transplant: midterm outcomes

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is used occasionally as a bridge to lung transplantation. The impact on mid-term survival is unknown. We analyzed outcomes after lung transplant over a 19-year period in patients who received ECMO support.

METHODS

From March 1991 to October 2010, 1,305 lung transplants were performed at our institution. Seventeen patients (1.3%) were supported with ECMO before lung transplant. Diagnoses included retransplantation (n = 6), pulmonary fibrosis (n = 6), cystic fibrosis (n = 4), and chronic obstructive pulmonary disease (n = 1). Fifteen patients underwent double lung transplant, one patient had single left lung transplant and one patient had a heart-lung transplant. Venovenous and venoarterial ECMO were implanted in eight and nine cases, respectively. Median duration of support was 3.2 days (range, 1 to 49 days). Mean patient follow-up was 2.3 years.

RESULTS

Thirty-day, 1-year, and 3-year survivals were 81%, 74%, and 65%, respectively, for the supported patients and 93%, 78%, and 62% in the control group (p = 0.56). Two-year survival was not affected by ECMO type, with survival of five out of nine patients supported by venoarterial ECMO vs seven out of eight patients supported by venovenous ECMO (p = 0.17). At 1- year follow-up, allograft function for the ECMO-supported patients did not differ from the control group (forced expiratory volume in one second, 2.35 L vs 2.09 L, p = 0.39) (forced vital capacity, 3.06 L vs 2.71 L, p = 0.34).

CONCLUSIONS

Extracorporeal membrane oxygenation as a bridge to lung transplantation is associated with higher perioperative mortality but acceptable mid-term survival in carefully selected patients. Late allograft function did not differ in patients who received ECMO support before lung transplant from those who did not receive ECMO.

Extracorporeal life support as a bridge to lung transplantation

Patients who are excellent candidates for lung transplantation often die on the waiting list because they are too sick to survive until an organ becomes available. Improvements in lung transplant outcomes, patient selection, and artificial lung device technologies have made it possible to bridge these patients to successful life-saving transplantation. Extracorporeal life support (ECLS) should be tailored to minimize morbidity and provide the appropriate mode and level of cardiopulmonary support for each patient's physiologic requirements. Novel device refinements and further development of ECLS in an ambulatory and simplified manner will help maintain these patients in better condition until transplantation.

An Investigation of Pulsatile Flow Past Two Cylinders as a Model of Blood Flow in an Artificial Lung

Pulsatile flow across two circular cylinders with different geometric arrangements is studied experimentally using the particle image velocimetry method and numerically using the finite element method. This investigation is motivated the need to optimize gas transfer and fluid mechanical impedance for a total artificial lung, in which the right heart pumps blood across a bundle of hollow microfibers. Vortex formation was found to occur at lower Reynolds numbers in pulsatile flow than in steady flow, and the vortex structure depends strongly on the geometric arrangement of the cylinders and on the Reynolds and Stokes numbers.

Use of extracorporeal membrane oxygenation as a bridge to primary lung transplant: 3 consecutive, successful cases and a review of the literature

Many transplant centers have considered extracorporeal membrane oxygenation (ECMO) to be a contraindication to lung transplantation, due to historically poor outcomes. However, recent advances in the technical aspects of ECMO have enabled patients to be supported with relative safety for several weeks until a donor lung becomes available. We present 3 young patients with acute (in 1 case, acute on chronic), severe respiratory failure that was refractory to conventional ventilation, who were placed on venovenous ECMO. In each case, a clinical decision was made that the patient's respiratory failure was irreversible and they were successfully managed with urgent lung transplantation.

Early institution of extracorporeal membrane oxygenation for primary graft dysfunction after lung transplantation improves outcome

BACKGROUND

Primary graft dysfunction (PGD) after lung transplantation (LTx) carries a significant mortality and clinical management is controversial. Extracorporeal membrane oxygenation (ECMO) has been used infrequently for recovery from acute lung injury (ALI) in this setting. We reviewed our experience with ECMO after primary LTx.

METHODS

The present study is a retrospective analysis of all LTx patients between 1991 and 2004. Twenty-two patients sustained severe PGD with subsequent placement on ECMO. We analyzed indications and 30-day, 1-year and 3-year mortality. Complications and incidence of multiple-organ failure (MOF) were determined. Critical appraisal of the evidence available to date was performed.

RESULTS

A total of 297 LTxs were performed during the study period, with 97.5%, 88.6% and 73.8% survival at 30 days, 1 year and 3 years, respectively. Twenty-two patients (7.9%) had severe allograft dysfunction leading to ECMO support. Twelve patients received single-lung (SLTx), 8 double-lung (BLTx), 1 single-lung/kidney (SLKTx) and 1 heart/lung (HLTx) transplantation. Thirty-day, 1-year and 3-year survival of LTx recipients with ECMO support post-operatively were 74.6%, 54% and 36%, respectively. MOF was the predominant cause of death (58.3%) in patients on ECMO support for PGD.

CONCLUSIONS

Our data suggest that, in addition to prolonged ventilation and pharmacologic support, ECMO should be considered as a bridge to recovery from PGD in lung transplantation. Early institution of ECMO may lead to diminished mortality in the setting of ALI despite the high incidence of MOF. Late institution of ECMO was associated with 100% mortality in this investigation.

Pulsatile flow past a cylinder: an experimental model of flow in an artificial lung

The focus of this study is an experimental apparatus that serves as a model for studying blood flow in a total artificial lung (TAL), a prototype device intended to serve as a bridge to lung transplantation or that supports pulmonary function during the treatment of severe respiratory failure. The TAL consists of hollow cylindrical fibers that oxygen-rich air flows through and oxygen-poor blood flows around. Because gas diffusivity in the TAL is very small, a convection mechanism dominates the gas transport, which is why we focus on the velocity around the fibers (modeled as a 0.05-cm-in-diameter and 5-cm-long cylinder). We designed a low-speed water tunnel to study the flow mechanism around the cylinder, across which the flow is generated by a linear actuator that allows different flow patterns to mimic the flow in a TAL. We tested the flow in the test section by numerical simulation and by the particle image velocimetry method to study the flow profile. The results show a uniform flow near the centerline of the water tunnel where the cylinder is placed. This decreases the effects of free-stream turbulence in the shear layers and reduces the uncertainty in determining the flow patterns around the cylinder. Knowledge gained from the flow around one cylinder (fiber) is beneficial for understanding vortex formation around multiple cylinders. We present a summary of vortex formation behind a cylinder for Reynolds numbers (Re) of 1, 3, and 5 and Stokes numbers (Ns) of 0.18 to 0.37; results show that higher Re and Ns favor vortex formation. These findings regarding the parameter range for vortex formation may provide principles for designing artificial lungs to enhance convective mixing. We anticipate that the pulsatile flow circuit presented here can be used to mimic the flow not only in TALs but in other physiological systems.

Bridge to lung transplantation with the novel pumpless interventional lung assist device NovaLung

BACKGROUND

Worsening of lung failure in patients awaiting a lung transplantation might lead to ventilation-refractory hypercapnia and respiratory acidosis. Most transplant centers consider pretransplantation extracorporeal membrane oxygenation as a contraindication for lung transplantation because of the poor outcome. We have, for the first time, applied the novel pumpless interventional lung assist NovaLung for bridge to lung transplantation in patients with severe ventilation-refractory hypercapnia. We report on our initial experience.

METHODS

Between March 2003 and March 2005, 176 lung transplantations were performed, of which 60% were high-urgency lung transplantations. Twelve of the high-urgency recipients had severe ventilation-refractory hypercapnia and respiratory acidosis. These patients were connected to the novel pumpless interventional lung assist NovaLung for bridge to lung transplantation.

RESULTS

The length of interventional lung assist NovaLung support was 15 +/- 8 days (4-32 days). PaO2, pH, and PaCO2 levels in arterial blood prior to interventional lung assist NovaLung implantation were 71 +/- 27 mm Hg, 7.121 +/- 0.1, and 128 +/- 42 mm Hg, respectively. Six hours after interventional lung assist NovaLung implantation, PaO2, pH, and PaCO2 levels had changed to 83 +/- 17 mm Hg (ns), 7.344 +/- 0.1 (P < .05), and 52 +/- 5 mm Hg (P < .05), respectively. Four patients died of multiorgan failure, 2 patients before and 2 after lung transplantation. Thus, 10 out of 12 patients were successfully bridged to lung transplantation, and 8 are still alive (1-year survival, 80%).

CONCLUSIONS

This report suggests that interventional lung assist NovaLung implantation is an effective bridge to lung transplantation strategy in patients with ventilation-refractory hypercapnia.

Critical care issues in lung and heart transplantation

Although much has been accomplished in HTx and LTx in the past few decades, much remains to be conquered. It is an ever-changing, always fascinating field. Though science and technology know no limits, the primary limitation of HTx and LTx continues to be the availability of donor organs. One can only hope that further advances in educating the public will help close the large gap between the list of those waiting and the organs available for transplantation.

Selective use of extracorporeal membrane oxygenation is warranted after lung transplantation

OBJECTIVES

Early allograft dysfunction after lung transplantation ranges from subclinical x-ray abnormalities to pulmonary edema, hypoxemia, hypercarbia, and pulmonary hypertension. Management may include extracorporeal circulation to allow recovery of the acute lung injury. We reviewed our experience with extracorporeal membrane oxygenation after lung transplantation to assess the utility of this therapy.

METHODS

A retrospective chart review was performed. Single or bilateral lung transplantation was performed in 444 adults from July 1988 to July 1998. Twelve (2.7%) patients experienced allograft dysfunction severe enough to require extracorporeal membrane oxygenation after failure of conventional therapy, including sedation, paralysis, and inhaled nitric oxide.

RESULTS

Seven of 12 patients requiring extracorporeal membrane oxygenation were discharged from the hospital. Mean and median times to extracorporeal membrane oxygenation support were 1.2 days and 0 days, respectively. Mean length of support was 4.2 days. Four patients died while receiving extracorporeal membrane oxygenation support. One patient was weaned from extracorporeal membrane oxygenation but died during the hospitalization. Two patients required acute retransplantation while receiving extracorporeal membrane oxygenation, and one survived to discharge. Three patients continued to receive extracorporeal membrane oxygenation support for more than 4 days, and all 3 died. All survivors had begun receiving extracorporeal membrane oxygenation support by post-transplantation day 1. Three of 7 patients discharged from the hospital died 12 months, 13 months, and 72 months after transplantation because of bronchiolitis obliterans syndrome (n = 2) or lymphoma (n = 1). Four patients are alive 2, 12, 25, and 54 months after transplantation.

CONCLUSIONS

Extracorporeal membrane oxygenation provides effective therapy for acute post-transplantation lung dysfunction. The frequency and pattern of our extracorporeal membrane oxygenation use reflects bias toward early extracorporeal membrane oxygenation support for isolated graft failure in otherwise intact and uninfected recipients.

Survival after acute graft failure in pediatric thoracic organ transplant recipients

Survival among recipients of repeat thoracic organ transplantation, particularly in the setting of acute graft failure (AGF), is lower than survival after a primary transplant. This has created controversy over the fair allocation of scarce organs. We reviewed our experience to assess the effectiveness of aggressive therapy and retransplantation in pediatric patients with AGF. Between November 1994 and March 1998, 52 patients aged 49 days to 16.9 years (median age 4.7 years) underwent thoracic organ transplantation (32 primary and 4 repeat heart, 16 primary and 4 repeat lung, and 3 primary heart-lung transplants). Acute graft failure occurred in nine (4 heart, 3 lung, 2 heart-lung transplants), six of whom were supported with extracorporeal membrane oxygenation (ECMO), and four of whom underwent repeat transplant. Six of the nine survived, including all of those who were retransplanted, and five of the nine were alive 1 year later. The average postoperative hospital stay after receiving a second organ was 46.5 days vs. a postoperative 22-day stay in recipients without AGF (p = 0.07). We conclude that the decision to allocate institutional and professional resources to the aggressive support of patients with AGF must be made at the level of the individual transplant center. However, we feel that the outcome of aggressive support and retransplantation justifies the allocation of organs to these patients and suggests that the current policies governing organ allocation for patients with early graft failure should be re-examined.

Lung transplantation--10-year experience

OBJECTIVE

The experience at our institution with various forms of lung transplantation (heart-lung, double lung and single lung) from December 1987 to September 1998 is reviewed and discussed.

METHODS

During this decade, 282 procedures (46 heart-lungs (HLTx), 142 double lungs (DLTx) and 94 single lungs (SLTx)) have been performed in 258 patients (140 male, 118 female; age: 38 +/- 13 years). Major indications included pulmonary fibrosis (n = 73), obstructive lung disease (n = 55), cystic fibrosis (n = 48), primary pulmonary hypertension (n = 36), secondary pulmonary hypertension (majority Eisenmenger's syndrome) (n = 30), and retransplantation (n = 24).

RESULTS

Early postoperative mortality (<90 days) was 13.9% (n = 36). The 1-, 3-, and 5-year survival rates in all recipients was 77, 70 and 63%, respectively. There was no significant difference in 1-year survival rates between the different procedures (HLTx: 78%, DLTx: 77%, SLTx: 77%). Significantly better 1-year survival was achieved in patients with cystic fibrosis (89%), pulmonary fibrosis (81%), obstructive lung disease (74%), and Eisenmenger's syndrome (83%) when compared to patients with primary pulmonary hypertension (55%). Survival rates remained unchanged during this period despite expanding indications during the last years. Causes of death in 90 recipients (HLTx: n = 19, DLTx: n = 37, SLTx: n = 34) included sepsis (n = 42), obliterative bronchiolitis (n = 28), cardiac failure (n = 5), and early allograft dysfunction (n = 2). Freedom from bronchiolitis obliterans syndrome (BOS) (>stage I ISHLT) was 80% at 1 year and 45% at 5 years.

CONCLUSIONS

Lung transplantation offers a true therapeutic option with good early and midterm results. Yet, chronic graft dysfunction represents a major obstacle for long-term benefit of this procedure.

Experience with lung transplantation

BACKGROUND

On the basis of a 5-year experience with heart transplantation and long-term animal experimentation, a lung transplantation program was instituted in 1987. After 10 years of experience, the entire patient population was reviewed.

METHODS

Hospital records were reviewed to evaluate the underlying diagnosis, year of transplantation, type of procedure, and long-term follow-up. The changing scope of indications, procedures performed, and donor criteria, as well as survival data for various subgroups of high-risk candidates, were also examined.

RESULTS

A total of 283 heart-lung (n = 46), single-lung (n = 94), and bilateral lung transplantation procedures (n = 143) were performed, with 22 patients undergoing 24 retransplantation procedures. The overall 5-year survival rate was 63%, with no difference between types of operations. Patients with cystic fibrosis, emphysema, pulmonary fibrosis, and secondary pulmonary hypertension showed similar survival rates; primary pulmonary hypertension was associated with a lower long-term survival. In all groups, the bronchiolitis obliterans syndrome occurred at a rate of approximately 15%/year.

CONCLUSIONS

Acceptable long-term results can be obtained with lung transplantation. Because of expanded indications, no survival benefit was gained in the overall population over a 10-year period. The major obstacle to true long-term survival remains the bronchiolitis obliterans syndrome.

Extracorporeal membrane oxygenation for lung transplant recipients with primary severe donor lung dysfunction

Primary severe donor lung dysfunction (DLD) is a significant complication after lung transplantation (LTx), and a high mortality is reported with conventional therapy. The purpose of this report is to review the experience of the University of Pittsburgh with extracorporeal membrane oxygenation (ECMO) for primary severe DLD after LTx. From September 1991 to May 1995, 220 LTx were performed at our center. Eight patients (8/220 = 3.6%) with severe DLD after LTx required ECMO support. The age of LTx recipients was 44 +/- 5 years (mean +/- SD); seven patients were female and one was male. Indications for LTx were: chronic obstructive pulmonary disease in four patients, bronchiectasis in two, and pulmonary hypertension in two. There were three single LTx and five bilateral LTx. The interval from LTx to institution of ECMO was 5.6 +/- 3.2 h (range 0-10 h). Three patients were supported with veno-venous (v-v) ECMO and five had veno-arterial (v-a) ECMO. The duration of ECMO support was 7.3 +/- 4.8 days (range 3-15 days). activated glotting time (ACT) was maintained between 110 and 180 s with intermittent use of heparin. Seven patients (7/8 = 87%) were successfully weaned from ECMO and six patients (6/8 = 75%) were discharged home; they are currently alive after a follow-up of 17 +/- 10.1 months. One patient died on ECMO support for refractory DLD and another died 2 months after ECMO wean from multisystem organ failure. At 6 months follow-up, forced expiratory volume in 1 s (FEV1) is 2.35 +/- 0.91 (75% +/- 17.4% predicted) and mean forced vital capacity (FVC) is 2.53 +/- 0.81 (64% +/- 14% predicted). We conclude that ECMO can be lifesaving when instituted early after primary severe DLD. The v-v ECMO support is preferred when the patient is hemodynamically stable and adequate long-term function of the allograft is anticipated.

Extracorporeal life support after heart or lung transplantation

Extracorporeal life support (ECLS) has been used in 10 patients after heart (5 patients), lung (3 patients), and heart-lung (2 patients) transplantation. The age range was 7 months to 55 years. Cardiopulmonary failure leading to institution of ECLS was due to acute postoperative organ malfunction in 4 patients (2 survived), subacute organ malfunction in 3 patients (none survived), and late rejection or infection in 3 patients (2 survived). Neurologic complications occurred in 3 patients (1 survived) and bleeding, in 5 patients (2 survived). Six patients (60%) were successfully weaned from ECLS, and 4 (40%) survived to leave the hospital. Survival was associated with younger age, shorter duration of ECLS, and longer interval from operation to initiation of ECLS but not to reason for initiating ECLS. Extracorporeal life support is feasible for sustaining both adults and children after heart, lung, or heart-lung transplantation. Best results were obtained in patients with conditions that, in retrospect, were treatable and reversible within days. More experience is needed to predict preoperatively which patients will benefit most from ECLS.

Extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation has now evolved into standard therapy for patients unresponsive to conventional ventilatory and pharmacological support. This article presents a clinical review of extracorporeal life support and its application to neonatal and pediatric patients as well as children requiring circulatory support after open heart surgery.

Double lung transplantation for adult respiratory distress syndrome after recombinant interleukin 2

Patients suffering from acute respiratory failure are considered poor candidates for lung transplantation (LT). We report a successful double lung transplantation performed in a patient with adult respiratory distress syndrome (ARDS). The 32-year-old woman received recombinant interleukin 2 (rIL-2) three months after an autologous bone marrow transplant for acute myelogenic leukemia as consolidation treatment. After four days of treatment with rIL-2, she developed ARDS which worsened over a three-week period, despite treatment. Lung transplantation was carried out as ultimate treatment. The postoperative course was uneventful. The patient is alive and in a good condition 11 months after LT. This case demonstrates the feasibility of LT in selected patients with ARDS. However, this case is exceptional since lung grafts should be utilized preferably for evaluated and accepted patients in transplant programs.