Liver transplantation using Donation after Cardiac Death donors

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1 Frontiers in Liver Transplantation Liver transplantation using Donation after Cardiac Death donors Diethard Monbaliu 1,, Jacques Pirenne 1,à, David Talbot 2, 1 Catholic University Leuven, Department of Abdominal Transplant Surgery, University Hospitals Leuven, Leuven, Belgium; 2 Freeman Hospital, Transplant Surgery, Newcastle upon Tyne, UK Summary The success of solid organ transplantation has brought about burgeoning waiting lists with insufficient donation rates and substantial waiting list mortality. All countries have strived to expand donor numbers beyond the standard Donation after Brain Death (DBD). This has lead to the utilization of Donation after Cardiac Death (DCD) donors, also frequently referred to as Non-Heart Beating Donors (NHBD). Organs from these donors inevitably sustain warm ischaemic damage which varies in its extent and affects early graft function as well as graft survival. As a consequence, non-vital organs such as renal transplants have increased rapidly from DCD donors but more vital organ transplants such as the liver have lagged behind. However, an increasing proportion of liver transplants are now derived from DCD donors. This article covers this expansion, current results, pitfalls, and steps taken to minimize complications and to improve outcome, and future developments that are likely to occur. Crown copyright Ó 2011 Published by Elsevier B.V. on behalf of the European Association for the Study of the Liver. Open access under CC BY-NC-ND license. Introduction Strategies to increase the supply of donor organs for liver transplantation Over the last five decades improvement in donor management, organ preservation, transplantation surgery, anaesthetic support as well as intensive care and immunosuppression have brought liver transplantation from an experimental technique to the preferred treatment option for end-stage liver failure. This treatment success has lead to an increased demand for liver donors whilst Received 6 January 2011; received in revised form 1 July 2011; accepted 4 July 2011 Corresponding author. Tel.: addresses: diethard.monbaliu@uzleuven.be (D. Monbaliu), (J. Pirenne), David.Talbot@nuth.nhs.uk (D. Talbot). Tel.: ; fax: à Tel.: ; fax: Abbreviations: DBD, Donation after Brain Death; NHBD, Non-Heart Beating Donor; DCD, Donation after Cardiac Death; HTK, Histidine Tryptophan Ketoglutarate solution; ITBS, Ischaemic Type Biliary Strictures; UW, University of Wisconsin solution; ECMO, Extra-Corporeal Membrane Oxygenation. the number of suitable grafts remained static. This critical organ shortage has been addressed in different ways. Firstly, there have been increased efforts to identify all potential brain dead donors with the aim of discussing organ donation with the donor s relatives. Secondly, whenever feasible, ideal (mostly young brain dead donors) livers are made available for splitting so potentially benefitting two recipients. Thirdly, living donor liver transplantation is another alternative, being in certain countries (e.g. Japan) virtually the only source of livers for transplantation. In contrast to living donation for children, living donation for adults is still associated with major complications and a substantial risk of death for the healthy volunteering living donor, and therefore has not gained more widespread acceptance. Finally, certain transplant units have advocated the use of extended criteria livers, previously known as marginal livers. These grafts, which in the main comprise steatotic, older and Donation after Cardiac Death (DCD) liver grafts, are known to be more prone to enhanced ischaemia reperfusion injury translated as primary graft non-function, early graft dysfunction or severe biliary tract damage. Steatotic livers are often dysfunctional in the early posttransplant period but once through this, they can function normally and provide normal graft survival. Advanced age should never be considered a contra-indication for transplantation but concomitant additional risk factors of delayed graft function (e.g. steatosis, donor hypernatraemia, prolonged cold ischaemia time) should be avoided. Many groups have revisited DCD to enlarge the deceased liver donor pool. Before the Harvard definition of brain death was established, the first liver transplants were done using DCD donors but the recipients had poor survival rates [1]. Thereafter, in the early nineties, with the increasing use of brain dead donors, there was only an occasional re-attempt in liver transplantation to use DCD livers though often again with unfavourable results [2]. However, this perspective had to be re-evaluated because of the general shortage of brain dead donor numbers and in part because of safety concerns for living donors. In addition, renal transplant units that have faced a much greater shortage of donor organs had already successfully turned back to the DCD donors and have increased transplant rates to the extent that in some cases waiting lists have declined. Historical perspective and donor types The pioneers of renal transplantation using kidneys from DCD donors met in 1995 in Maastricht and published a consensus statement which most importantly identified four categories of Journal of Hepatology 2012 vol. 56 j

2 Table 1. The classification of DCD donors as originally described by the First International Workshop on NHB donors that was organised in Maastricht in The term controlled and uncontrolled were not used at the workshop but added later. (Reproduced from Talbot and D Alessandro [45,85], and Kootstra [3,4] by Permission of Oxford University Press, Inc.). Categorie of non-heart beating donors JOURNAL OF HEPATOLOGY Category Alternative categorization Status of potential donor Hospital department Process I Uncontrolled Dead upon arrival Accident and emergency Viability testing II Uncontrolled Resuscitation attempted without success Accident and emergency Viability testing III Controlled Awaiting cardiac arrest Intensive care Transplantation IV Controlled Cardiac arrest while brain dead Intensive care Transplantation what was then termed the Non-Heart Beating Donor (Table 1) [3,4]. The term controlled and uncontrolled were not used at the Maastricht workshop but added later. The important aspect of these definitions is that those donors (and organs) exposed to least ischaemia (controlled) or more ischaemia (uncontrolled) were identified. This went someway to explain the variable early results of liver transplantation from these donors. Controlled DCD refers to donation that follows an anticipated death occurring after planned removal of life-sustaining treatment such as mechanical ventilation, and organ perfusion support. In contrast, uncontrolled DCD involves a sudden, unexpected cardio-pulmonary arrest and unsuccessful resuscitation. For the uncontrolled DCD donor, death was either confirmed outside of hospital (Maastricht I) but the donor was still brought to hospital; or death was declared after unsuccessful resuscitation after witnessed cardiac arrest (Maastricht II) usually in the Accident and Emergency unit. In these situations, there was a very variable period of ischaemic damage due to cardiac standstill followed by cardiac resuscitation which obviously would have a varied degree of effectiveness. After death was declared and the transplant team called-in, there would be sometimes continued resuscitation which some termed organ resuscitation or no activity at all before the transplant team commenced true organ perfusion usually by cannulation of the femoral vessels and the installation of in vivo organ preservation measures. This was followed by laparotomy and organ preservation, usually after consent was obtained from the next of kin and judiciary. The efficacy of cooling the abdominal organs usually with only femoral cannulation was suboptimal but could be augmented by peritoneal cooling [5]. A no touch period was recommended by the Maastricht consensus meeting to ensure that death after cardiac standstill had become irreversible. This period of no touch has now been incorporated in most DCD protocols. In 1995, a period of 10 min was chosen though subsequently shortened to a minimum of 5 min as recommended by the Institute of Medicine [6]. The UK has recently incorporated this period into the definition of death, that is to say that there should be a minimum of 5 min after the heart has stopped before death is declared [7]. At this point in time there is no need for a further no touch period. Controlled DCD occurs after a decision of futility of care has been made usually by the Intensive Care staff and treating physicians, independently of organ donation. When the planned withdrawal of life-sustaining support is discussed with the relatives, organ donation can be brought up by the relatives or by the medical team. If appropriate, the transplant team is contacted and present before vital life support is withdrawn. Different liver retrieval techniques for DCD have been described in the early nineties. D Allessandro et al. from the University of Wisconsin installed femoral cannulation prior to withdrawal of life support. After declaration of death, abdominal organs were flushed with University of Wisconsin (UW) solution, removed en bloc and transported to the transplant center for additional back-table dissection and transplantation [8]. Alternatively, other centers cannot install femoral cannulation before withdrawal of life support and so intravascular perfusion with cold preservation fluid occurs after declaration of death but still on the intensive care. The body is then moved to the operating theatre where organ procurement is commenced. However, interventions such as femoral cannulation before withdrawal of life support are only practiced in few units. Indeed, such interventions may not be regarded in the patient s interest and therefore not widely allowed or legalized. Another retrieval technique referred to as the super-rapid technique was described by Cassavilla et al. from the Pittsburgh group [2]. A rapid laparotomy and rapid aortic cannulation are performed after the patient is pronounced dead. Organ perfusion is usually commenced within 4 min, followed by cross-clamping the thoracic aorta and venous decompression via sternotomy. Thereafter, cannulation and perfusion of the portal vein with topical cooling using iced slush take place before procurement. This super-rapid technique is now commonly used for controlled DCD by most abdominal procurement teams. Current practice and outcome of DCD liver transplantation Over the last decade, controlled DCD liver transplantation has been a fast growing source of liver grafts in countries with the necessary legal framework across Europe and the US (Tables 2 and 3). Consequently, DCD nowadays represents as much as 20% of the liver donor pool in some European countries (Fig. 2). Despite this growth and initial enthusiasm, only recently a tendency to establish worldwide common guidelines regarding the exact definition of cardiac death, length of warm ischaemia, no touch period, or optimal preservation methods have been reported [9]. Most local, national and international registry data concur and show that, compared to DBD, DCD recipients experience inferior graft survival mainly related to higher rates of biliary complications, notably Ischaemic Type Biliary Strictures (ITBS) [10 17] (Table 4 and Fig. 1). In fact, for DCD livers, an adjusted odds ratio for graft failure of 1.85 compared with DBD livers has been reported [11]. Not surprisingly, lower (but usually statistically not significant) to equal patient survivals have been reported Journal of Hepatology 2012 vol. 56 j

3 Frontiers in Liver Transplantation Table 2. Number of DCD liver transplantations per total number of liver transplantations per country with a legal framework for DCD. DCD donors. However, this tendency was not followed by an absolute/general increase in the total number of livers transplanted in these countries No. % No. % No. % No. % No. % No. % Spain 5/ / / / / / Belgium 5/ / / / / / The Netherlands 8/ / / / / / United Kingdom 28/ / / / / / United States 185/ / / / / / In Spain, only uncontrolled DCD are utilized for liver transplantation (Organización Nacional de Trasplantes) versus controlled DCD in Belgium, the Netherlands (Annual report Eurotransplant 2009) and the UK (UK Transplant); in the US (UNOS database), both controlled and uncontrolled are used for liver transplantation. Table 3. Overview of differences amongst specific legislation on the use of DCD donors for organ transplantation between different countries. All DCD types allowed Uncontrolled DCD allowed by single institutions and by national registry analyses. However, according to a recent meta-analysis [18] and Scientific Registry of Transplant Recipients analysis [19], DCD recipients had a 1.6% increased odds of one year patient mortality and experience a worse survival at one and three years compared to DBD. The increasing experience with DCD liver transplantation has identified donor-specific risk factors associated with poorer graft survival outcomes (donor warm ischaemia time >20 30 min, cold ischaemia time >8 10 h and donor age >40 60) [15,16,20]. Nevertheless, favourable and equivalent outcome between DCD and DBD liver transplantation have been reported by single centres [21 23]. Similar graft survival has even been reported for DCD livers older than years compared to younger DCD livers [21,24]. Additionally, examining the United Network for Organ Sharing database, Mateo et al. showed similar graft survival rates for both DCD and DBD when transplanting low-risk organs in low-risk recipients [16]. Of note, no significant association between DCD liver transplant volume and graft outcome has been demonstrated [10]. In addition, conversion of potential liver donors to actual liver transplants is low. Indeed, transplant teams probably use stricter criteria of transplantability for DCD livers than for DBD livers as a substantial number (up to 45%) of DCD livers are turned down in situ [25]. This low conversion rate is even lower for uncontrolled DCD donors. In 2008, only 18.2% (14 out of 77) potential uncontrolled DCD donors were used as liver donors by the Barcelona group (personal communication C. Fondevilla). Complications of livers from DCD donors No DCD allowed Belgium France Germany The Netherlands Spain Hungary United Kingdom Ireland United States Austria Poland Initial major concerns emerging from the early series using DCD liver grafts comprised an increased incidence of primary graft non-function [2,8,13]. As previously described though partial function is often encountered, the definition of primary nonfunction necessitating regrafting seems to vary quite considerably between units. Consequently, regrafting rates also vary between units. Hepatic artery thrombosis was also believed to be more common after liver transplantation using DCD donors and if so may be due to the reduction of run off as a result of in situ blood stasis in the arterial tree during the period of warm ischaemia [26]. Endothelial damage by ischaemia leading to loss of surface glycosamino-glycans (heparin) further increases the chance of thrombosis [27]. This risk of hepatic artery thrombosis can probably be reduced by heparin administration immediately prior to therapy withdrawal in the donor, a practice not allowed in UK, but generally accepted in Belgium and the Netherlands. In contrast to the initial reports, most contemporary series now show equivalent incidences of primary graft non-function and hepatic artery thrombosis [17]. The statement of Sir Roy Calne on biliary complications being the real Achilles heel of liver transplantation is particularly true for DCD liver transplantation [28]. Besides bile duct leakage, anastomotic strictures, bile duct stones, casts, or sludge, ITBS or ischaemic cholangiopathy currently remains the major concern. A higher ITBS incidence of 16% following DCD liver transplantation compared to 3% in DBD recipients was recently reported [18]. DCD recipients had a 10.8 times increased odds ratio of ITBS. Different risk factors for ITBS have also been identified and comprise donor WIT, donor age >40 and CIT >8 h [17,29]. This translates into a higher rate of graft loss and retransplantation leading to a blunted enthusiasm or even tendency to abandon further use of DCD liver grafts. Although the pathogenesis of ITBS remains to be elucidated, various factors including hepatic artery patency, ischaemia reperfusion injury, cytomegalo-virus infection, chronic ductopenic rejection, ABO incompatibility, and toxic factors have been suggested to play a role [30]. Ischaemic lesions are understandably brought about by thrombosis in situ of small vessels which produces biliary ischaemia, leading to biliary leaks and strictures. Another possible mechanism of biliary strictures comes from the composition of the bile which changes with increasing warm ischaemia. An increased bile salt to phospholipids ratio occurs within bile after reperfusion [31]. This changed content could therefore be instrumental in producing more damage though it could also reflect the damage that has already occurred. Finally, the biliary epithelium is quite vulnerable to ischaemia reperfusion injury [32]. Consequently, any additional period of warm ischaemia prior to preservation as in DCD liver grafts may exert an additional deleterious damage and risk for ITBS compared to 476 Journal of Hepatology 2012 vol. 56 j

4 Table 4. Overview of outcome after Donation after Cardiac Death (DCD) liver transplantation in historical order of publication, referring to the number of transplantations performed, the patient and graft survival, rate of primary non-function (PNF) and biliary complications. Whenever appropriate, predictive factors of outcome such as cold ischemia time (CIT), donor warm ischemia time (DWIT) are given. Author, year, [Ref.] Reich et al., 2000, [9] Abt et al., 2004, [13] Manzarbeitia et al., 2004, [22] Muiesan et al., 2005, [25] Pine et al., 2009, [86] Grewal et al., 2009, [21] Dubbeld et al., 2010, [87] De Vera et al., 2009, [15] Nguyen et al., 2009, [34] Marthur et al., 2010, [52] Foley et al., 2011, [17] Jay et al., 2011, [19] No. Time of DCD period, LTx % of all transplants , , , , , , , , , 4 Patient survival at 1, 3, 5 and, 10 years (%) Graft survival at 1, 3, 5 and, 10 years (%) No. of retx (%) Predictive factors of outcome Total biliary complication rate, % (nonanastomotic, strictures) 100, -, -, - 100, -, -, - 0 / , 72, -, - 70, 63, -, - 14 Risk factors for graft loss (univariate) Life support Dialysis Pre-op PT CIT Risk factors for graft loss (multivariate) CIT 90, 84 (2 yr), -, - / 11 / , 80, -, - 86, 78, -, (3) 3?? / / 30 (20) 5 92, 88, 88, - 79, 75, 71, - 15 / - (8) / 85, 80, -, - 74, 68, -, - 18 Risk factors for graft loss (multivariate) CIT DWIT DCD was a risk factor for non-anastomotic strictures 79, -, 70, 57 69, -, 56, Risk factor for graft loss (multivariate): DWIT >20 min MELD >30 Recipient BMI >30 Risk factor for retransplantation (multivariate): Recipient age >60 yr Risk factor for bile duct complications (multivariate): Donor age >60 yr Risk factor for PNF/DGF (multivariate): Male donor to female receptor Recipient age >60 yr Recipient BMI >30 yr 27 (24) 2 PNF (%) (16) 12 90, 90, 90, - 74, 68, 63, - 16 / 26 (11) , 78, -, - 78, 65, -, - 14 Risk factors for graft loss in DCD: Recipient: Age >55 yr Male sex African-American Metabolic disorders MELD score >35 Hospitalized Life support at Tx HCV positivity Donor: Age >50 yr Weight >100 kg DWIT >35 min CIT >6 h Predictors for mortality: Recipient: Age >55 yr retx Hospitalized Donor: Weight >100 kg CIT >6 h , 14 84, -, 68, 54 69, -, 56, 43 1-yr retx rate , 71, -, JOURNAL OF HEPATOLOGY Development of overall biliary complications (univariate) Donor age and donor age >40 yr Development of ischemic cholangiopathy (multivariate) CIT >8 h Donor age >40 yr Development of anastomotic biliary strictures (univariate) Donor weight Donor BMI Amplification of mortality risk when DCD combined with CIT >12 h / / 47 (34) 2.3 Journal of Hepatology 2012 vol. 56 j

5 Frontiers in Liver Transplantation Graft survival (%) Years DBD donors >60 DBD donors DCD donors Extended criteria DBD donors Fig. 1. Graft survival at 1, 2, and 3 years after liver transplantation using standard criteria DBD donors (black line), extended criteria DBD donors (blue line), >60 DBD donors (grey dotted line), and DCD donors (red line). Data from the Collaborative Transplant Study (CTS). DBD. The resulting biliary strictures that occur after transplantation can be either localized and thereby easy to manage radiologically/endoscopically [33,34]. However, more often than not they are diffuse and so difficult to manage being an indication for retransplantation [34]. Importantly, these ITBS translate in substantial recipient morbidity including biliary sepsis, growth of multi-resistant organisms and deteriorating health status which eventually might exclude those recipients from relisting. Moreover, liver function usually remains well-maintained and the associated low MELD score does not therefore reflect the severity of their disease. In the current era of MELD-based allocation, these patients can only regain true access to a retransplantation through an exceptional MELD status. Whether these patients currently get prioritized for a retransplantation depends thus on the practise of the local organ allocation organization or a change in the MELD allocation system as advocated by some groups [10,35]. Most importantly, these complications translate into increased utilization of resources including retransplantation, repeated and prolonged hospital admissions, and endoscopic retrograde cholangiopancreaticography or percutaneous transhepatic cholangiography. Consequently, these complications result in increased costs and persistent [18] patient suffering [36]. Why DCD organs and particularly DCD livers are regarded as suboptimal? Perhaps the most effective step in organ preservation is the cooling of the organ as the metabolic rate is halved for every 10 C drop in temperature. In DBD donors, the aorta is clamped and perfusion starts at the same time. Therefore the organs make a single step from warm, oxygenated and metabolically active to cold, hypoxic and metabolically almost inactive. Organs from DCD donors are not procured under ideal conditions as they may have suffered from a period of hypotension and hypoxia followed by the cardiac arrest. This varying duration of cellular and tissue hypoxia leads to anaerobic metabolism and lactic acidosis. At best, this produces cells that have an oxygen and cellular energy debt that needs to be recovered before they can function normally. The cellular energy state before transplantation is an important indicator of transplant recovery. At worst, the cells have already died and, even with restoration of a warm oxygenated blood supply, will not recover and subsequently will lyse, discharging their contents into the recipients blood supply. The hepatocellular damage is evident by the significant rise of transaminases usually substantially higher after DCD versus DBD liver transplantation. An organ is essentially composed of a large number of units (lobules for the liver) made up of cells; the organ will function according to how many cells are alive and functioning, alive but not functioning or dead. This is compounded by the fate of its blood supply. After cardiac arrest, if perfusion is delayed, in situ thrombosis will prevent organ perfusion and promote necrosis with a paradoxical low level of transaminases after transplant. With such potential damage, it may take a protracted time for an organ to work normally. Another important mechanism leading to further aggravated cellular injury takes place during the restoration of blood flow. The so-called ischaemia reperfusion injury invariably takes place in every graft during reperfusion in the recipient albeit its severity is variable and more severe in DCD livers. The extent of injury depends on the degree of activation of key players involved in the hepatic ischaemia reperfusion injury including Kupffer cells, platelets and leukocytes, besides the generated pro-inflammatory response (oxidative stress, inflammatory cytokines, cytoplasmatic proteases, up regulation of pro-inflammatory transcription factors). Clinically, ischaemia reperfusion injury can result in immediate graft function, delayed graft function (considered to occur in 10 30% of grafts) or primary graft non-function (considered to occur in <5% of grafts), respectively. Delayed graft function is characterized by (i) ongoing hepatocellular injury as suggested by rising serum transaminase concentrations, (ii) poor hepatic synthetic function as evidenced by elevated prothrombin times despite continuous fresh frozen plasma (FFP) infusion, (iii) minimal bile production, (iv) inability to clear metabolic waste products as suggested by hyperammonemia, and (v) patent hepatic vasculature demonstrated by duplex ultrasound. In contrast to primary graft non-function, liver function in recipients with delayed graft function usually starts to improve by the third post-transplant day, whereas those with primary graft non-function will continue to worsen. The time course is best illustrated by the kidney where the incidence of delayed graft function from such DCD donors is higher than for DBD donors. The recipient may need prolonged dialysis before the kidney function has recovered from the additional warm ischaemic damage to which it has been exposed. In comparison to recipients of DBD kidneys, the creatinine levels in DCD recipients are often still higher at 3 months but equal by 6 months. The occurrence of primary non-function (never to function) is established by a prolonged wait with no function and its occurrence is partially influenced by donor criteria such as donor age and previous morbidity but very importantly by the duration of the donor warm ischaemia (time between withdrawal of life support and effective cold perfusion) and variable degree of hypoperfusion occurring before death. The sometimes protracted period of clinical recovery is well understood for the kidney and probably would be similar for the liver if there was an adequate liver support mechanism which could be used like dialysis. However, because this is not the case, a harder definition of primary non-function is used for the liver transplant where it has to function almost immediately. In addition, most liver transplant centres would only use Maastricht III or IV donors (with the exception of Spain as discussed later). They would choose their donors carefully if they intended to use the liver i.e. young donors with normal or recovering liver function tests and a terminal illness which is likely to lead to rapid cardiac 478 Journal of Hepatology 2012 vol. 56 j

6 death on withdrawal of support. After withdrawal of support, the agonal period would have to be short otherwise the donor would only be used as a kidney donor. The period of warm ischaemia should be short too (discussed later). The liver would be inspected in vivo and should be adequately flushed with a normal macroscopic appearance (e.g. not steatotic). The transplant professionals would then try to minimise all other negative aspects that could influence transplant outcome such as short cold ischaemia, appropriate recipient selection, etc. After transplantation, they would expect a partial function before full recovery such as improving acidosis but worsening clotting, protracted periods of cholestasis, etc. though the decision to re-transplant for primary non-function is a difficult one and open to much variation between specialists and units. Steps taken to improve outcome after DCD liver transplantation (Table 4) Limit warm ischaemic time Primarily, this means just using controlled DCD donors which are expected to sustain minimal primary warm ischaemic damage. In some countries, this approach is thus not possible as is the case in Spain, France, and Italy (Table 3). In Spain and France, the use of controlled (Maastricht category III) DCD donors is not legal. In Italy, determination of death requires by law a 20-min flat ECG [37]. To overcome this substantial ischaemic damage, a normothermic in situ approach is used prior to procurement as described below. With the simple cold approach as is common in the UK, Belgium and the Netherlands, the most optimal is that the withdrawal of therapy takes place in the operating theatre or that the donor is rapidly transferred to the operating theatre where a super rapid laparotomy as described by Casavilla et al. [2] is performed usually followed by a dual flush (portal and aortic) with cold preservation solution. This means that the abdominal organs are cooled more effectively than if femoral cannulation is performed on the intensive care unit followed by a more leisurely transfer to operating theatre for laparotomy. Meanwhile, some modifications on the super rapid laparotomy for easier and more rapid control of the distal aorta have been described [38,39]. Secondly, warm ischaemia time is still not well defined. Current definitions vary (i) from the time from withdrawal of support until start of cold perfusion (total warm ischaemia time) [9], or (ii) from the time from cardiac arrest to cold perfusion, or (iii) only reflect the period of time during the agonal phase (systolic arterial pressure lower than e.g. 50 mm Hg) [40]. Indeed, the time to death after withdrawal of life support (referred to as agonal phase or withdrawal phase) is highly variable [41]. More importantly, this period which includes a sustained hypotension before cardiac arrest may have a substantial impact on the warm ischaemic damage DCD organs are subjected to. In one study, prolonged severe hypotension (systolic pressure of less than 50 mm Hg for more than 15 min) following withdrawal of treatment was associated with increased rates of biliary ischaemia, graft loss and death after liver transplantation [42]. Some authors have therefore suggested to not only report on the time between withdrawal of life support to cardiopulmonary cessation but to distinctively report on the period of hypotension. In addition, DCD donor characteristics that may predict rapid death after withdrawal of life support are being identified and JOURNAL OF HEPATOLOGY validated [41,43]. Finally, to further limit warm ischaemia, DCD organ procurement should ideally be done by experienced surgeons (Table 5). Optimize distribution of preservation solution by means of a warm fibrinolytic preflush, and an initial low viscosity preservation solution Throughout impaired perfusion during the agonal phase and eventually after cardiac arrest, in situ thrombosis may occur within the vascular system. Therefore, the standard use of heparin is probably insufficient and thrombolytics are more effective for the uncontrolled DCD in particular. Alternatively, heparin can be administered prior to the withdrawal of therapy in controlled DCD donors. However, administration of drugs is ethically regarded unacceptable in some countries because of the lack of any benefit for the donor. Such a thrombolytic approach using streptokinase has been proven effective in small and large animal models of DCD liver transplantation. This was followed by a randomised prospective blinded clinical trial of human donors which found a significant improvement of kidneys from uncontrolled DCD donors which sustain the maximal damage [44]. Not surprisingly, controlled DCD donors showed less of a benefit; however with larger numbers this could likely show benefit [45]. To be maximally effective, the thrombolytic agent should be added as a warm pre-flush or should at least be administered at the beginning of the flush when the intravascular temperature is likely to be normal before effective cooling has occurred. It is anticipated that a significant high volume flush has to occur after administration of fibrinolytics so as to minimise the chance of transferring the agent from the donor to the recipient. There is probably some apprehension of using such agents where the liver is to be transplanted. Their use is not widespread though no problems have been reported to date with their use in donors when the liver has been transplanted. Low viscosity solutions for perfusion, such as Histidine Tryptophan Ketoglutarate (HTK), have been suggested to be more effective for organs from DCD as they allow a better flush-out of the microcirculation, including the small peri-biliary capillaries [46]. However, a retrospective study analyzing United Network for Organ Sharing (UNOS) data has suggested that flush and storage of livers in HTK after retrieval from DCD have a poorer outcome in comparison to University of Wisconsin (UW) solution [47]. Therefore combining a low viscosity flush for the arterial (such as HTK or Marshall s solution) and portal perfusion with the more viscous University of Wisconsin solution seems an attractive combination [25]. In situ pressurized perfusion [48] or pressurised arterial back table flushing have shown to reduce biliary complications in DBD liver transplantation and might be transferred to DCD practise [49]. Some experienced centres also advocate decompressing the inferior vena cava first, prior to start the aortic flush to avoid detrimental congestion of the liver which is already inherently present following circulatory arrest [25]. Minimize cold preservation time There has long been a view that although in general cold ischaemia is a negative factor for organ storage, this is more of an issue for organs from DCD donors. This has been confirmed in large Journal of Hepatology 2012 vol. 56 j

7 Frontiers in Liver Transplantation Table 5. Strategies to optimize the outcome of DCD liver transplantation along the time line of the different steps during the course of organ donation, preservation and transplantation and their status (clinically applied vs. preclinical status). Time period Principle Solution Status Donor Flush-out Preservation Recipient Donor pretreatment Avoid extended warm ischaemia time Discard livers with in situ warm ischaemia >30 minutes Improve complete flush-out Warm prefibrinolytic pre-flush of the microcirculation Inital flush with low viscosity preservation solution Final flush-out with UW (high viscosity-gold standard preservation solution) Limit cold ischaemia Allocation of the liver to the procuring transplant center Transplant livers as soon as possible Select a recipient in whom the hepatectomy is expected to be of short duration Alternative cold perfusion solutions Ex vivo preservation by machine perfusion In vivo normothermic recirculation Reducing the ischaemia reperfusion injury Cytoprotective additives to the perfusion solution Oxygenated hypothermic machine perfusion preservation Hypothermic oxygenated machine perfusion preservation ex vivo normothermic liver perfusion in vivo normothermic liver perfusion using ECMO Select a recipient who may tolerate dysfunction Multi-factorial biological modulation strategy Ethically difficult Preclinical status Preclinical status but clinically applied in a safety and feasibility trial for normal livers Preclinical status Preclinical status Preclinical status animal DCD models where primary graft non-function could be avoided when an additional period of 4 h cold ischaemia after a substantial period (60 min) of warm ischaemia was either omitted or replaced by e.g. normothermic ex vivo machine perfusion preservation [50,51]. This experimental evidence thus demonstrated that not the warm ischaemia per se but the combination of warm and cold ischaemia is deleterious. Similar findings have been reported for the kidney by the Cambridge group which reviewed the UK renal transplant outcome and have found that a cold ischaemic time >12 h doubles the chance of primary non-function for kidneys from DCD donors [51]. A recent data analysis from the Scientific Registry of Transplant Recipients data revealed that for each hour increase in cold ischaemia time there was a 6% increase in graft failure rate [52]. Normothermic liver perfusion utilising Extra-Corporeal Membrane Oxygenation technology UK 12% Belgium 18% The Netherlands 21% Normothermic in vivo recirculation utilizing Extra-Corporeal Membrane Oxygenation (ECMO) technology has become the main approach for uncontrolled DCD donors by the Barcelona [53] and Madrid [54] units and recently followed in Paris (personal communication B. Barrou). Similarly, it is utilized by certain American transplant units (notably Michigan and Madison, USA) for controlled DCD donors [55,56]. The main purpose is twofold: first to allow organs to recover in situ from warm ischaemic Spain ~1% Fig. 2. Liver transplantation from DCD donors amongst different European countries in Numbers of liver transplantations from DCD donors presented as percentages of the total number of deceased liver transplantations per country. 480 Journal of Hepatology 2012 vol. 56 j

8 damage by providing adequate oxygen and nutrients at physiological temperatures to reverse the ATP loss; second to avoid cold ischaemia immediately after the organs have suffered in situ warm ischaemia. Importantly, during normothermic perfusion, there is evidence that at least for the kidney cytoprotective proteins such as heme oxygenase-1 can be upregulated [57], tissue repair can be stimulated [58] and that immunomodulation therapy can be used [59]. For uncontrolled DCD donors, the Spanish groups diagnose death after unsuccessful resuscitation outside the hospital but cardio-pulmonary resuscitation is continued until the body is transferred to hospital [60]. As described by Fondevilla et al. [53] on admission a femoral vessel cut down is performed and ECMO is commenced with an occlusive balloon placed in the aorta at the level of the diaphragm via the opposite femoral artery. Once abdominal ECMO has started, the transplant team has up to 4 h to obtain consent for donation from next of kin and the judiciary. Liver tests can be performed and liver function can be evaluated biochemically. Donation then occurs whilst the ECMO continues. Another advantage is the feasibility of assessing viability of the perfused organ de visu, like in a standard procurement procedure; in this situation if the donor is young, the perfusion of the liver is good, the bile duct well-vascularised and the biliary epithelium healthy, the surgeon can decide to accept the liver for transplantation. For controlled DCD donors as for the Michigan approach, the aim is to improve the quality of the liver by reducing the warm ischaemic damage. Therefore, the procedure is discussed before withdrawal of support for the potential donor. An upper aortic balloon is usually employed with ECMO to prevent oxygenated blood returning to the heart and head for obvious reasons. Again, this approach allows the relatives more time with their loved one and the body can be moved to theatre more leisurely with the system fully operating. Also the organ retrieval can be performed in a more methodical way, hopefully having already admitted the intended liver recipient early to minimise cold ischaemia further. Livers are briefly cold stored following the initial normothermic in situ preservation. This approach is logistically very demanding and if done inappropriately (the liver kept warm with no oxygenation) it may complete the destruction of the organ probably more effectively than if no preservation had been attempted! The selection of the most appropriate recipient Because of the significantly higher risk of graft failure, a patient receiving a liver from a DCD donor should be able to withstand a period of uncertain function but at the same time gain a significant survival benefit from receiving such a graft. Some centers therefore allocate DCD livers to stable patients with hepatocellular carcinoma or with a low MELD score but the allocation for DCD livers is not often reported on [21,23]. Thereby, most liver transplant professionals would consider a patient with fulminant liver failure a poor choice of recipient though this has been done in certain situations. This consideration is in line with the concept of the donor risk index which identified DCD (amongst other independent donor characteristics) as having a greater risk of graft failure compared to whole DBD livers [61]. Consequently, livers from DCD donors should not be used in the lowest risk recipients where their risk of death would be significantly increased by a DCD liver whilst neither should they be used in the highest risk patient where delayed graft function would be JOURNAL OF HEPATOLOGY poorly tolerated. To minimize cold ischaemic time, recipients should ideally be chosen where a straightforward hepatectomy is anticipated, in particular recipients that have not undergone previous liver surgery including a redo liver transplant. Another strategy to minimize the cold ischaemia time is to start the recipient procedure as soon as the donor liver is judged to be transplantable by the procurement surgeon [17]. Albeit currently not supported by data, patients with cholestatic diseases (e.g. primary sclerosing cholangitis) with an inherent susceptibility to develop de novo or recurrent biliary strictures are often regarded inappropriate candidates for DCD liver transplantation. Since ITBS has also been found associated with immunological factors such as PSC, some transplant centers avoid liver transplantation of DCD grafts in PSC recipients and thus the cumulative risk of developing biliary strictures [62]. Another controversy is whether to accept DCD liver grafts for hepatitis C virus positive recipients since DCD liver transplantation has also been suggested to be a risk factor for increased hepatitis C virus recurrence in these hepatitis C virus positive recipients [21,63,64]. Indeed, the extent of the ischaemia reperfusion injury in the graft amongst other factors has been associated with more aggressive or accelerated HCV recurrence [65,66]. However, Tao et al. did not observe an adverse effect of DCD on hepatitis C virus recurrence [67]. Similarly, no increase of complications nor untoward effects of disease progression was observed in a larger cohort of 77 DCD liver grafts transplanted into hepatitis C positive recipients, compared to 77 unmatched non-hcv recipients [68]. How many livers are being transplanted from DCD donors? In the UK, there has been a general decline in brain dead donors in part as a result of improvement in neurosurgery, seat belt legislation etc. (Fig. 3). Over the last few years, there has been an increase in the number of DCD donors which has largely followed the promotion of multi-organ donation. The primary beneficiary of this increase has been renal transplantation, the expansion of liver transplantation from such donors having lagged behind. One of the concerns expressed by many was that DBD was being converted into DCD and thus eroding the DBD donor pool instead of expanding the number of organ donors. Possible explanations for this may relate to the excessive enthusiasm and erroneous perception amongst ICU teams that DCD is as good as DBD. Secondly, DCD may offer the opportunity to avoid prolonging the ICU management until brain death occurs whilst saving an unnecessary regarded waiting period for the relatives and an unnecessary use of ICU resources. Such a substitution phenomenon would obviously have a detrimental effect on liver donation and on the overall results of liver transplantation. Whilst this undoubtedly has occurred, in the UK the expansion of DCD livers is greater than the decline of DBD livers. However, most countries that have started DCD programmes have seen a reduction in DBD programmes whereas DBD has remained stable in countries without DCD activity [69]. If there is a substitution phenomenon or at least an independent decline of DBD in the presence of a successful DCD, this can be reversed as shown by the Dutch transplant community who experienced their massive increase in DCD sometime ago (Fig. 4). They subsequently launched a publicity initiative directed towards ICU personnel and transplant Journal of Hepatology 2012 vol. 56 j

9 Frontiers in Liver Transplantation Number coordinators and consequently retained DCD numbers and have re-expanded the number of brain dead donors. The future of liver transplantation from DCD donors Improved liver preservation Year Donation after brain death Donation after cardiac death Fig. 3. In the UK, an increase of the number of DCD is accompanied by a decrease in the number of DBD and this may reflect in part a phenomenon of substitution (early conversion of potential DBD into DCD) (Courtesy of Mark Jones from UK Transplant and Darius Mirza, Birmingham, UK). The expansion of liver transplants has not kept up with kidney transplants from DCD donors so that currently there are a number of livers that are not being used. This is because these livers are viewed as too marginal and therefore transplant professionals consider the risk of e.g. primary non-function or graft dysfunction to be too great. Therefore, there is a need to either improve the quality of these livers by such measures as ECMO support of the donor after death, or a liver preservation technique that improves the chance of immediate function after transplantation. For the kidney, two randomised trials of hypothermic machine perfusion with an acellular cold perfusion have shown opposite conclusions with one trial showing reduced delayed graft function with machine perfusion [70,71] and the other no Number Year Donation after brain death Donation after cardiac death Fig. 4. Erosion of the DCD into the DBD donor pool as experienced in the Netherlands (courtesy of the Dutch Transplantation Society and from R. Porte). difference [72] albeit there were some substantial differences between the design (statistics) and the methods used in these studies [73]. Despite these differences, hypothermic machine perfusion of DCD livers has been put forward [74]. Machine perfusing the liver is not easy with the dual blood supply although there has been some encouraging data from New York Presbyterian hospital observing favourable early graft function following hypothermic machine perfusion [75]. However in this first report, normal livers from standard criteria donors that would have functioned equally well without hypothermic machine perfusion were perfused. Whether this method is applicable and advantageous for human DCD and other extended criteria donor livers needs to be further evaluated. Alternatively, normothermic ex vivo liver perfusion seems to offer another way forward. Here, a machine perfusion system is used to pump oxygenated blood around a circuit including the liver with appropriate pressures for the artery and vein. With this approach, the liver can be tested to determine function and therefore could be transplanted subsequently with greater confidence that the outcome would be successful. The Oxford group has developed and used such a perfusion rig for porcine DCD livers that have been subsequently successfully transplanted despite having been exposed to long and otherwise fatal warm ischaemic periods [76]. Such an approach has already been developed clinically for the lung where pulmonary function by means of gas transfer can be tested prior to transplantation [77,78]. The orthostatic lung changes from the patients terminal illness has shown to be readily reversed with ex vivo ventilation and perfusion with either leukocyte-free blood or a suitable acellular solution (e.g. the so-called Steen solution). A final approach for extended criteria (though not DCD) livers has been described by the Essen group which has used the University of Bonn s approach of retrograde oxygen persufflation during the preservation period. Oxygen is pumped into a closed infra-hepatic vena cava forcing its way out through the substance of the liver and through small puncture holes placed through the dome of the liver for the purpose [79]. The group has successfully used this approach in humans for steatotic livers or for livers from donors with hypernatraemia [80]. Whilst seemingly a bizarre treatment, it has been around for quite some time and has been used before for the human kidney and it could have a role for DCD organs that have experienced an oxygen debt under normothermic conditions [81]. Besides optimized preservation, protective strategies can be implemented after liver transplantation in the recipient. These strategies should focus to optimize the microcirculation upon reperfusion and to minimize the inflammatory response that ensues the transplantation particularly from DCD donors. In numerous animal studies, a variety of substances have been tested effectively but so far not successfully applied in humans. Such a strategy of attenuating the ischaemia reperfusion injury lies in combining several drugs that act simultaneously on the self-perpetuating inflammatory cascade. As an example, the Leuven multifactorial modulation protocol was recently developed in a porcine DCD liver transplantation model. This cocktail included streptokinase, epoprostenol during a warm preflush of the donor liver and the IV administration during the reperfusion in the recipient of glycine, glutathione, alpha-tocopherol, apotransferrin, alpha-1-glycoprotein, and a MAPK-kinase inhibitor [82]. With this cocktail, primary graft non-function was eliminated and the bile salt toxicity reduced in a clinically relevant 482 Journal of Hepatology 2012 vol. 56 j

10 model of primary non-function following exposure of porcine livers to 45 min of warm ischaemia and 4 h of cold ischaemia. Further expansion of the DCD donor pool? Besides the use of uncontrolled DCD donors, organ donation following euthanasia can be regarded as another DCD category where there is no risk of substitution from DBD into DCD donors. With the gradual acceptance of euthanasia as a suitable end of life pathway in certain countries (e.g. Belgium and the Netherlands), it is becoming evident that euthanasia can be followed by successful organ donation [83,84]. Such a process involves the establishment of cardiac death as in a classical controlled DCD which is then followed by laparotomy, perfusion and organ donation. Such an approach is perhaps the ultimate DCD donor as the potential donor gives full consent himself rather than being the responsibility of a relative. In addition, their blood group and tissue type can be established before death and the potential recipients admitted before death. Such an approach though strange to the extent of making the donor surgeon very uncomfortable is the logical sequence after the legalisation of euthanasia. Needless to say and similar to other DCD types, the decision of end of life is taken independently of a possible organ donation (and teams in charge of performing the euthanasia are independent of transplant teams). Conclusions There has been a recent expansion of multi-organ donors as a result of DCD. This expansion has mainly come from controlled DCD donors though some countries have a contribution from uncontrolled donors. The expansion has mainly benefitted non vital organs such as the kidney because of the concern of the impact of early graft dysfunction and primary non-function of the graft such as the liver. With careful selection, DCD livers can be used as a valuable source of livers for transplantation and there are possible steps that can be taken to minimize damage to the liver and thereby promote the chances of primary function if used. The proportion of livers used from these donors is likely to increase but the decline in brain dead donors should not be accepted as inevitable and the use of DBD donors should be continuously promoted. Suitable recipients of DCD livers are those that can tolerate some degree of partial function i.e. not fulminant or very sick patients. Further work is needed to recover livers if they are judged to be unsuitable for transplant. Euthanasia could potentially produce a new source of organs in those countries where such an approach to terminal care is legal. Using DCD donors to expand the donor pool has challenged the transplant community on several grounds. The definition of cardiac death, defined as the irreversible cessation of circulatory and respiratory function, has challenged the ethical and medical professionals to accurately define death, leading to newly developed consensus statements on cardiac death. The current gold standard of organ preservation (simple cold storage) has proven to be insufficient to preserve these organs. As such, protective measures against ischaemic injury are being developed. Increased attention and initiatives to promote DCD as a donor pool enlarging strategy (and thus not at the cost of DBD) remain crucial. Financial support D.M. and J.P. hold a chair of the Centrale Afdeling voor Fractionering (CAF) Vilvoorde, Belgium. JP has received research funding from Roche and Astellas. D.T. has received research funding from the Northern Counties Kidney research fund, Royal College of Surgeons of England and Edinburgh, UK Transplant, Technology Strategy board, Aquix, Roche, Astellas and Novartis. Conflict of interest The authors declared that they do not have anything to disclose regarding funding or conflict of interest with respect to this manuscript. Acknowledgements The authors thank Mark Jones from NHS blood transplant for providing current DCD liver data for UK, and US, and Darius Mirza for data from UK; Constantino Fondevilla and Beatriz Dominguez-Gil for providing Spanish data; Axel Rahmel for providing Eurotransplant data (Belgium and the Netherlands); Robert Porte for providing data from the Netherlands; Gerhard Opelz for providing data from the Collaborative Transplant Study; Francesca de Pace for providing Italian data; and Benoit Barrou for providing French data. The authors are grateful to Lydia Coolen and Veerle Heedfeld for the editorial assistance. References JOURNAL OF HEPATOLOGY [1] Starzl TE, Marchioro TL, Porter KA, Brettschneider L. Homotransplantation of the liver. 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