Extracorporeal Membrane Oxygenation as a Bridge to Lung Transplantation

The article by Shafii et al.1 describes their initial experience using extracorporeal membrane oxygenation (ECMO) or extracorporeal lung support (ECLS) as a bridge to lung transplantation (LTx). Nineteen patients were placed on ECMO as an intention to bridge to transplantation, and finally 14 were transplanted after a mean of 6 days on support. Of these, 10 were alive at 1 year representing 75% post-LTx 1 year survival or 55% 1 year survival on an intention-to-treat basis. Although these numbers represent inferior survival to the general non-ECMO–supported lung transplant population, the vast majority of this very sick patient population would die before a life-saving transplant if ECMO was not available. Although largely disappointing results of adult ECMO bridge to transplant was the rule in the initial years of LTx,2 recent improvements in patient selection, a better understanding of ventilator-associated lung injury,3 and improvements in artificial lung device technologies have made it possible to successfully bridge selected extremely sick patients to LTx.4–8 Although the literature on the topic is limited to small series of patients such as in the article by Shafii et al.,1 recent larger studies including a randomized trial have shown very promising results with the use of ECMO technology in adults with survival rates ranging from 50% to 80% as opposed to 10–20% in the 80s.9 This includes the experience from Michigan in 100 patients,10 the UK Conventional ventilation or ECMO for Severe Adult Respiratory failure (CESAR trial),11 and H1N1/acute respiratory distress syndrome reports.12,13 Although these studies represent a different patient population compared to patients with end-stage lung disease awaiting for LTx, it does demonstrate that the rate of complications have dramatically decreased and the management of these patients have significantly improved compared to the past. The outcomes of patients bridged to LTx using mechanical support have also been better. A recent review from the United Network for Organ Sharing experience totaling 51 patients bridged to LTx with ECMO from 1987 to 2008 showed a 1, 6, 12, and 24 month survival of 72%, 53%, 50%, and 45%, respectively, compared to 93%, 85%, 79%, and 70% for unsupported patients, respectively.14 Many other recent reports from experienced centers in both LTx and ECMO have shown that 80% or more of patients can be successfully bridged to LTx and outcomes after LTx in these selected patients can approach that of conventional lung transplants.4,5,7,8,15–18 In ECMO modes, most patients can be supported by either venovenous (VV) ECMO (hypoxia with or without hypercapnia) or pumpless AV using interventional lung assist device (iLA; Novalung, Heilbronn, Germany) (hypercapnia). The exception to that is patients with primary pulmonary hypertension or patients with significant secondary pulmonary hypertension associated with interstitial lung disease and right ventricular failure where venoarterial (VA) ECMO or pumpless pulmonary artery to left atrium pumpless iLA should be used. Our group in Toronto has an excellent experience with the later approach.7 One of the most important achievements in the recent ECMO era is the concept of ambulatory ECMO, which can be achieved by avoiding groin cannulation whenever possible. To that end, the dual lumen Avalon cannula for VV ECMO has been a major advance.19,20 Patients are no longer waiting for transplant paralyzed and bed ridden. Instead, active physiotherapy with physical reconditioning has been the case. One recent report demonstrated that outcomes of these patients have been quite similar to conventional transplants of intensive care unit and hospital length of stay and thus much different than the previous ECMO experience where patients generally had a very slow recovery and protracted course.21 In our experience, at least half of our patients are now extubated while on ECMO and many of them are ambulatory. It should therefore be the mind-set of the ECMO team in the current era to work toward that goal as soon as the patient is stabilized. We always discuss institution of ECMO as soon as the patient is assessed for mechanical ventilation, and certainly wherever possible, we try to avoid any prolonged ventilation time and physical deconditioning prior to ECMO initiation. Usually, these patients have already been assessed by the LTx team and listed for LTx; however, in exceptional instances, urgent assessments and listing while on ECMO can be performed. Given the level of resource utilization and the scarcity of donor organs, careful patient selection is still clearly needed. No specific patient selection criteria to determine candidacy for ECMO as bridge to LTx can yet be suggested due to the small number of reported cases, but in general, young age, absence of multiple-organ dysfunction, and good prospects for rehabilitation should be considered. With the growing population of older interstitial lung disease patients in the lung transplant waiting lists who present with rapid functional deterioration, a selection criteria for ECMO in this specific population will become imperative so that treatment is not futile and does not impair end-of-life objectives. In conclusion, although experience is still limited, ECMO clearly can be an effective tool to bridge critically ill patients to a life-saving lung transplant. Technological advances have permitted safer, less complicated application of ECMO for longer periods. Support can be tailored to minimize morbidity and provide the appropriate ECMO mode and level of cardiopulmonary support for each specific patient’s physiologic requirements. Novel device refinements and further development of ECMO in an ambulatory and simplified manner will help to maintain these patients in better condition until transplantation. Further experience is required to ultimately define the optimal criteria and patient population for application of ECMO in patients requiring bridging to LTx. Data on long-term results and quality of life measurements in this patient population are still lacking and should be an important end-point for future research.

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