Effects of Intraoperative Support Strategies on Endothelial Injury and Clinical Lung Transplant Outcomes

Extracorporeal membrane oxygenation vs cardiopulmonary bypass in lung transplantation: an updated meta-analysis

AIM

This meta-analysis aimed to compare the outcomes of extracorporeal membrane oxygenation (ECMO) and cardiopulmonary bypass (CPB) in lung transplantation.

METHODS

We searched PubMed, Embase, and Cochrane databases for studies comparing ECMO to CPB in lung transplantation. Odds ratios (ORs) for binary endpoints and mean differences (MDs) for continuous outcomes were calculated with 95% confidence intervals (CIs). DerSimonian and Laird random-effects model was applied for all endpoints. I2 statistics was used to assess heterogeneity.

RESULTS

Fourteen studies with a total of 1797 patients were included. ECMO was associated with significant reductions in hepatic dysfunction (OR 0.47, 95% CI 0.25-0.90), hemodialysis (OR 0.62, 95% CI 0.43-0.88), severe graft rejection (OR 0.43, 95% CI 0.23-0.78), one-year mortality (OR 0.70; 95% CI 0.51 to 0.98; p = 0.04; I2 = 13%) and tracheostomy rates (OR 0.62, 95% CI 0.46-0.86). Additionally, ECMO reduced the length of hospital stay (MD - 5.69 days, 95% CI - 9.31 to - 2.08) and ICU stay (MD - 6.02 days, 95% CI - 8.32 to - 3.71). However, ECMO was associated with longer total ischemic time (MD 61.07 min, 95% CI 3.51 to 118.62). No significant differences were observed for stroke, thromboembolic events, atrial fibrillation, or 30-day and 3-year mortality.

CONCLUSIONS

ECMO offers perioperative advantages in lung transplantation, reducing postoperative complications, one-year mortality, and recovery time compared to CPB. However, the longer total ischemic time with ECMO warrants further investigation into its long-term outcomes.

TRIAL REGISTRY

International Prospective Register of Systematic Reviews; N°: CRD42024604049; URL: https://www.crd.york.ac.uk/prospero/ .

Current status of routine use of veno-arterial extracorporeal membrane oxygenation during lung transplantation

INTRODUCTION

Recently, there has been growing experience with utilizing a veno-arterial extracorporeal membrane oxygenator (VA ECMO) routinely during lung transplantation procedures. Yet, there is a lack of consensus on the protocols, benefits, and outcomes of routine VA ECMO use in lung transplantation.

AREAS COVERED

This article presents an overview of the current status of routine use of VA ECMO during lung transplantation, including rationale, protocols, applications, and outcomes.

EXPERT OPINION

Utilization of VA ECMO during lung transplantation has emerged as an alternative mechanical circulatory support modality to cardiopulmonary bypass, with growing evidence showing lower rates of peri-operative complications. Some groups took that further into routine application of VA ECMO during lung transplantation. The current available evidence suggests that routine utilization of VA ECMO during lung transplantation is associated with lower rates of primary graft dysfunction and improved early outcomes. Use of VA ECMO allows controlled reperfusion of the allograft and avoids an unplanned "crash" on pump in case of hemodynamic instability, which carries worse outcomes after lung transplantation. As a relatively new approach, further follow-up of growing experience, as well as prospective clinical trials, is necessary to develop a consensus about routine utilization of VA ECMO during lung transplantation.

Exploring the Impact of Extracorporeal Membrane Oxygenation on the Endothelium: A Systematic Review

Extracorporeal membrane oxygenation (ECMO) is a life-saving intervention for patients with circulatory and/or pulmonary failure; however, the rate of complications remains high. ECMO induces systemic inflammation, which may activate and damage the endothelium, thereby causing edema and organ dysfunction. Advancing our understanding in this area is crucial for improving patient outcomes during ECMO. The goal of this review is to summarize the current evidence of the effects of ECMO on endothelial activation and damage in both animals and patients. PubMed and Embase databases were systematically searched for both clinical and animal studies including ECMO support. The outcome parameters were markers of endothelial activation and damage or (in)direct measurements of endothelial permeability, fluid leakage and edema. In total, 26 studies (patient n = 16, animal n = 10) fulfilled all eligibility criteria, and used VA-ECMO (n = 13) or VV-ECMO (n = 6), or remained undefined (n = 7). The most frequently studied endothelial activation markers were adhesion molecules (ICAM-1) and selectins (E- and P-selectin). The levels of endothelial activation markers were comparable to or higher than in healthy controls. Compared to pre-ECMO or non-ECMO, the majority of studies showed stable or decreased levels. Angiopoietin-2, von Willebrand Factor and extracellular vesicles were the most widely studied circulating markers of endothelial damage. More than half of the included studies showed increased levels when compared to normal ranges, and pre-ECMO or non-ECMO values. In healthy animals, ECMO itself leads to vascular leakage and edema. The effect of ECMO support in critically ill animals showed contradicting results. ECMO support (further) induces endothelial damage, but endothelial activation does not, in the critically ill. Further research is necessary to conclude on the effect of the underlying comorbidity and type of ECMO support applied on endothelial dysfunction.

Heparanase-induced endothelial glycocalyx degradation exacerbates lung ischemia/reperfusion injury in male mice

The endothelial glycocalyx (eGC) is a carbohydrate-rich layer on the vascular endothelium, and its damage can lead to endothelial and organ dysfunction. Heparanase (HPSE) degrades the eGC in response to cellular stress, but its role in organ dysfunction remains unclear. This study investigates HPSE's role in lung ischemia-reperfusion (I/R) injury. A left lung hilar occlusion model was used in B6 wildtype (WT) and HPSE genetic knockout (-/-) mice to induce I/R injury in vivo. The left lungs were ischemic for 1 h followed by reperfusion for 4 h prior to investigations of lung function and eGC status. Data were compared between uninjured lungs and I/R-injured lungs in WT and HPSE-/- mice. WT lungs showed significant functional impairment after I/R injury, whereas HPSE-/- lungs did not. Inhibition or knockout of HPSE prevented eGC damage, inflammation, and cellular migration after I/R injury by reducing matrix metalloproteinase activities. HPSE-/- mice exhibited compensatory regulation of related gene expressions. HPSE facilitates eGC degradation leading to inflammation and impaired lung function after I/R injury. HPSE may be a therapeutic target to attenuate graft damage in lung transplantation.

Mitigating the risk of inflammatory type primary graft dysfunction by applying an integrated approach to assess, modify and match risk factors in lung transplantation

Long-term outcome following lung transplantation remains one of the poorest of all solid organ transplants with a 1- and 5-year survival of 85% and 59% respectively for adult lung transplant recipients and with 50% of patients developing chronic lung allograft dysfunction (CLAD) in the first 5 years following transplant. Reducing the risk of inflammatory type primary graft dysfunction (PGD) is vital for improving both short-term survival following lung transplantation and long-term outcome due to the association of early inflammatory-mediated damage to the allograft and the risk of CLAD. PGD has a multifactorial aetiology and high-grade inflammatory-type PGD is the result of cumulative insults that may be incurred in one or more of the three variables of the transplantation continuum: the donor lungs, the recipient and intraoperative process. We set out a conceptual framework which uses a fully integrated approach to this transplant continuum to attempt to identify and, where possible, modify specific donor, recipient and intraoperative PGD risk with the goal of reducing inflammatory-type PGD risk for an individual recipient. We also consider the concept and risk-benefit of matching lung allografts and recipients on the basis of donor and recipient PGD-risk compatibility. The use of ex vivo lung perfusion (EVLP) and the extended preservation of lung allografts on EVLP will be explored as safe, non-injurious EVLP may enable extensive inflammatory testing of specific donor lungs and has the potential to provide a platform for targeted therapeutic interventions on lung allografts.

Early serum biomarkers to characterise different phenotypes of primary graft dysfunction after lung transplantation: a systematic scoping review

Background

Lung transplantation (LUTX) is often complicated by primary graft dysfunction (PGD). Plasma biomarkers hold potential for PGD phenotyping and targeted therapy. This scoping review aims to collect the available literature in search of serum biomarkers for PGD phenotyping.

Methods

Following JBI and PRISMA guidelines, we conducted a systematic review searching MEDLINE, Web of Science, EMBASE and The Cochrane Library for papers reporting the association between serum biomarkers measured within 72 h of reperfusion and PGD, following International Society for Heart and Lung Transplantation (ISHLT) guidelines. We extracted study details, patient demographics, PGD definition and timing, biomarker concentration, and their performance in identifying PGD cases.

Results

Among the 1050 papers screened, 25 prospective observational studies were included, with only nine conducted in the last decade. These papers included 1793 unique adult patients (1195 double LUTX, median study size 100 (IQR 44-119)). Most (n=21) compared PGD grade 3 to less severe PGD, but only four adhered to 2016 PGD definitions. Enzyme-linked immunosorbent assays and the multiplex bead array technique were utilised in 23 and two papers, respectively. In total, 26 candidate biomarkers were identified, comprising 13 inflammatory, three endothelial activation, three epithelial injury, three cellular damage and two coagulation dysregulation markers. Only five biomarkers (sRAGE, ICAM-1, PAI-1, SP-D, FSTL-1) underwent area under the receiver operating characteristic curve analysis, yielding a median value of 0.58 (0.51-0.78) in 406 patients (276 double LUTX).

Conclusions

Several biomarkers exhibit promise for future studies aimed at PGD phenotyping after LUTX. To uncover the significant existing knowledge gaps, further international prospective studies incorporating updated diagnostic criteria, modern platforms and advanced statistical approaches are essential.

Which strategy is better for lung transplantation: Cardiopulmonary bypass or extracorporeal membrane oxygenation?

Background: In lung transplantation surgery, extracorporeal life support (ECLS) is essential for safety. Various support methods, including cardiopulmonary bypass (CPB) and off-pump techniques, are used, with extracorporeal membrane oxygenation (ECMO) gaining prominence. However, consensus on the best support strategy is lacking.Purpose: This article reviews risks, benefits, and outcomes of different support strategies in lung transplantation. By consolidating knowledge, it aims to clarify selecting the most appropriate ECLS modality.Research Design: A comprehensive literature review examined CPB, off-pump techniques, and ECMO outcomes in lung transplantation, including surgical results and complications.Study Sample: Studies, including clinical trials and observational research, focused on ECLS in lung transplantation, both retrospective and prospective, providing a broad evidence base.Data Collection and/or Analysis: Selected studies were analyzed for surgical outcomes, complications, and survival rates associated with CPB, off-pump techniques, and ECMO to assess safety and effectiveness.Results: Off-pump techniques are preferred, with ECMO increasingly vital as a bridge to transplant, overshadowing CPB. However, ECMO entails hidden risks and higher costs. While safer than CPB, optimizing ECMO postoperative use and monitoring is crucial for success.Conclusions: Off-pump techniques are standard, but ECMO's role is expanding. Despite advantages, careful ECMO management is crucial due to hidden risks and costs. Future research should focus on refining ECMO use and monitoring to improve outcomes, emphasizing individualized approaches for LT recipients.