Mark K. Ferguson (ed.)Difficult Decisions in Surgery: An Evidence-Based ApproachDifficult Decisions in Thoracic Surgery3rd ed. 2014An Evidence-Based Approach10.1007/978-1-4471-6404-3_20
© Springer-Verlag London 2014
20. Extracorporeal Support for Lung Grafts Prior to Transplantation
(1)
Department of Thoracic, Transplant and Cardiovascular Surgery, Hannover Medical School, Carl-Neuberg-Str.1, Hannover, 30625, Germany
Abstract
Because of the limitations of cold preservation, only optimal donor organs are selected for transplantation; not all potential donor lungs are accepted as suitable for transplantation. Ex-vivo lung perfusion techniques are seeing increased use in lung transplant surgery, the major point of interest being the possibility to recondition marginal donor organs. In addition, a portable organ care system has been developed to completely avoid the use of cold ischemia with its resulting negative consequences. The question of whether this approach will result in a potential benefit to normal lung transplant surgery has yet to be answered.
Keywords
Extracorporporeal circulationLung transplantationEx vivo lung perfusionLung preservationIntroduction
Despite a steady improvement in organ donor management and the establishment of standardized methods for preserving donor organs, not all potential donor lungs are accepted as suitable for transplantation. Flushing or rinsing with cold perfusion solution has, for many years, been regarded as the current Gold Standard for preserving lung grafts, as for other solid organs. Despite the fact that there are a number of solutions available for lung transplantation, with the choice of method depending very much on the specific preferences of individual clinics, these solutions do not differ greatly with regard to the post-cold flush perfusion ischemia times achieved. For lungs preserved in this manner, an ischemic limit of 10 h is currently indicated. Harvesting and implantation with subsequent reperfusion should then take place directly, as a more protracted ischemia may lead to a higher risk of primary graft failure and, consequently, a marked decline in the survival rate. Owing to this narrow time frame and the resulting limitations of cold preservation, only optimal donor organs are selected for transplantation. This relatively high rejection rate of potential donor lungs is due to the fear of a less-than-optimal donor organ being additionally damaged by cold preservation, adversely affecting the outcome of transplantation.
Over the last few years, intensive research has been conducted on the development of normothermic perfusion systems for donor lungs. With Ex-vivo Lung Perfusion (EVLP), developed in Sweden in 2007, the donor lung is connected to a system of tubes, similar to a heart-lung machine, and a respirator. With a normothermic system, it is possible to evaluate marginal donor organs and assess organ function using parameters such as oxygen intake, lung elasticity and perfusion and ventilation pressure, to determine their suitability for the transplantation process. Moreover, the cold ischemic time can be reduced through the use of this type of normothermic organ perfusion, thus preventing any potential harm to the donor organ from a lack of oxygen and nutrients.
Search Strategy
We used Medline and PubMed as a database with the search terms “extracorporporeal circulation”, “lung transplantation”, “ex vivo lung perfusion” and “lung preservation” for relevant literature published until July 1, 2013.
Results
Ex-vivo Reconditioning of Marginal Donor Lungs Using EVLP
Some working groups, particularly those in Lund (Sweden), Toronto (Canada) and Vienna (Austria), already avail of clinical experience in evaluating and improving donor lungs through the use of EVLP and subsequent transplantation [1–4]. In these initial clinical operations, marginal donor lungs which originally appeared to be unsuitable for transplantation were assessed more accurately using normothermic EVLP and successfully transplanted, achieving comparable results to transplants conducted after cold preservation.
The potential to perfuse donor organs with poor oxygenation performance and oedema has also been demonstrated, where the use of a hyperosmolar solution led to significant oedema reduction and a subsequent improvement in oxygenation performance [5]. Normothermic EVLP was thus used not only in the further appraisal of marginal donor lungs but also in the therapeutic application of hyperosmolar solution in the treatment of edematous tissue.
Further thoughts along these lines open up the possibility of reconditioning marginal donor lungs using EVLP in the ex-vivo treatment of a pulmonary oedema and a pulmonary embolism using fibrinolytic agents to apply a surfactant to the airways and administer a high dose of antibiotic therapy for pneumonia, culminating in feasible immunomodulatory therapies [6]. The practical application of this pioneering technology initially requires the conventional removal of the donor lungs after an antegrade perfusion with a quality suitable solution for cold preservation. This preservation can, if necessary, be combined with subsequent retrograde flushing through the pulmonary veins to remove smaller pulmonary emboli. Typically, the standard method of preservation and packing is then to use ice with normothermic EVLP technology, when moving the donor organ to the transplant clinic after transport. The donor organ is surgically prepared for this purpose, using an aseptic technique.
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