Assessment of graft function before liver transplantation: quest for the lost ark?

Liver Graft Machine Perfusion: From History Perspective to Modern Approaches in Transplant Surgery

The shortage of donor organs remains an unresolved issue in livertransplantation worldwide. Consequently, strategies for expanding the donor pool are currently being developed. Donors meeting extended criteria undergo thorough evaluation, as livers obtained from marginal donors yield poorer outcomes in recipients, including exacerbated reperfusion injury, acute kidney injury, early graft dysfunction, and primary nonfunctioning graft. However, the implementation of machine perfusion has shown excellent potential in preserving donor livers and improving their characteristics to achieve better outcomes for recipients. In this review, we analyzed the global experience of using machine perfusion in livertransplantation through the history ofthe development ofthis method to the latest trends and possibilities for increasing the number of liver transplants.

Role of Machine Perfusion in Liver Transplantation

Given the current severe shortage of available livers for transplantation, there is an urgent need to maximize the utilization of donor organs. One of the strategies to increase the number of available livers for transplantation is to improve organ utilization through the use of elderly, overweight, or organs donated after circulatory death. However, the utilization of these "marginal" organs was associated with an increased risk of early allograft dysfunction, primary nonfunction, ischemic biliary complications, or even re-transplantation. Ischemia-reperfusion injury is a key mechanism in the pathogenesis of these complications.

Evolution of dynamic, biochemical, and morphological parameters in hypothermic machine perfusion of human livers: A proof-of-concept study

INTRODUCTION

Hypothermic machine perfusion (HMP) is increasingly investigated as a means to assess liver quality, but data on viability markers is inconsistent and the effects of different perfusion routes and oxygenation on perfusion biomarkers are unclear.

METHODS

This is a single-centre, randomised, multi-arm, parallel study using discarded human livers for evaluation of HMP using arterial, oxygen-supplemented venous and non-oxygen-supplemented venous perfusion. The study included 2 stages: in the first stage, 25 livers were randomised into static cold storage (n = 7), hepatic artery HMP (n = 10), and non-oxygen-supplemented portal vein HMP (n = 8). In the second stage, 20 livers were randomised into oxygen-supplemented and non-oxygen-supplemented portal vein HMP (n = 11 and 9, respectively). Changes in dynamic, biochemical, and morphologic parameters during 4-hour preservation were compared between perfusion groups, and between potentially transplantable and non-transplantable livers.

RESULTS

During arterial perfusion, resistance was higher and flow was lower than venous perfusion (p = 0.001 and 0.01, respectively); this was associated with higher perfusate markers during arterial perfusion (p>0.05). Supplementary oxygen did not cause a significant alteration in the studied parameters. Morphology was similar between static and dynamic preservation groups. Perfusate markers were 2 fold higher in non-transplantable livers (p>0.05).

CONCLUSIONS

Arterial only perfusion might not be adequate for graft perfusion. Hepatocellular injury markers are accessible and easy to perform and could offer insight into graft quality, but large randomised trials are needed to identify reliable quality assessment biomarkers.

The promise of organ and tissue preservation to transform medicine

The ability to replace organs and tissues on demand could save or improve millions of lives each year globally and create public health benefits on par with curing cancer. Unmet needs for organ and tissue preservation place enormous logistical limitations on transplantation, regenerative medicine, drug discovery, and a variety of rapidly advancing areas spanning biomedicine. A growing coalition of researchers, clinicians, advocacy organizations, academic institutions, and other stakeholders has assembled to address the unmet need for preservation advances, outlining remaining challenges and identifying areas of underinvestment and untapped opportunities. Meanwhile, recent discoveries provide proofs of principle for breakthroughs in a family of research areas surrounding biopreservation. These developments indicate that a new paradigm, integrating multiple existing preservation approaches and new technologies that have flourished in the past 10 years, could transform preservation research. Capitalizing on these opportunities will require engagement across many research areas and stakeholder groups. A coordinated effort is needed to expedite preservation advances that can transform several areas of medicine and medical science.

Lipidomics comparing DCD and DBD liver allografts uncovers lysophospholipids elevated in recipients undergoing early allograft dysfunction

Finding specific biomarkers of liver damage in clinical evaluations could increase the pool of available organs for transplantation. Lipids are key regulators in cell necrosis and hence this study hypothesised that lipid levels could be altered in organs suffering severe ischemia. Matched pre- and post-transplant biopsies from donation after circulatory death (DCD, n = 36, mean warm ischemia time = 2 min) and donation after brain death (DBD, n = 76, warm ischemia time = none) were collected. Lipidomic discovery and multivariate analysis (MVA) were applied. Afterwards, univariate analysis and clinical associations were conducted for selected lipids differentiating between these two groups. MVA grouped DCD vs. DBD (p = 6.20 × 10(-12)) and 12 phospholipids were selected for intact lipid measurements. Two lysophosphatidylcholines, LysoPC (16:0) and LysoPC (18:0), showed higher levels in DCD at pre-transplantation (q < 0.01). Lysophosphatidylcholines were associated with aspartate aminotransferase (AST) 14-day post-transplantation (q < 0.05) and were more abundant in recipients undergoing early allograft dysfunction (EAD) (p < 0.05). A receiver-operating characteristics (ROC) curve combining both lipid levels predicted EAD with 82% accuracy. These findings suggest that LysoPC (16:0) and LysoPC (18:0) might have a role in signalling liver tissue damage due to warm ischemia before transplantation.

Normothermic liver preservation: a new paradigm?

Despite increasing donor numbers, waiting lists and pre-transplant mortality continue to grow in many countries. The number of donor organs suitable for liver transplantation is restricted by cold preservation and ischemia-reperfusion injury (IRI). Transplantation of marginal donor organs has led to renewed interest in new techniques which have the potential to improve the quality of preservation, assess the quality of the organ and allow repair of the donor organ prior to transplantation. If successful, such techniques would not only improve the outcome of currently transplanted marginal livers, but also increase the donor pool. Experimental evidence suggests that preservation under near physiological conditions of temperature and oxygenation abrogates IRI. Normothermic perfusion maintains the organ in a physiological state, avoiding the depletion of cellular energy and the accumulation of waste products, which occurs with static cold storage. It enables viability assessment prior to transplantation thereby reducing the risk of transplanting inherently marginal organs. Here we review the use of normothermic machine perfusion as a means of organ preservation.

Assessing warm ischemic injury of pig livers at hypothermic machine perfusion

BACKGROUND

Livers originating from donation after circulatory death (DCD) donors are exposed to warm ischemia (WI) before liver transplantation (LTx). Currently, there are no objective tests to evaluate the damage sustained before LTx. This study aims to identify surrogate markers for liver injury that can be assessed during hypothermic machine perfusion (HMP) preservation. In addition, we want to use mathematical equation modeling combining these markers to improve our assessment of DCD livers for transplantation.

MATERIALS AND METHODS

Porcine livers were exposed to incremental periods of WI (0-120 min) and subsequently HMP preserved for 4 h. Biochemical and hemodynamic parameters were repeatedly measured in the perfusate during HMP. Subsequently, to mimic LTx, normothermic isolated-liver perfusion was applied for 2 h and the injury assessed using a morphological score.

RESULTS

With increasing WI periods, the perfusate became more acidotic, and levels of aspartate aminotransferase (AST), liver fatty acid binding protein, redox-active iron, and arterial vascular resistance increased. A damage index, combining AST and pH (damage index = 2 - 37 × β(AST) - 257 × β(pH)) based on multifactorial analysis of the changing pattern of these markers, had increased sensitivity and specificity to reflect WI and reperfusion injury.

CONCLUSIONS

This proof of concept study demonstrated the potential role for objective evaluation of DCD porcine livers during HMP and the advantage to use multifactorial analysis on the markers' changing pattern.

Donation after cardio-circulatory death liver transplantation

The renewed interest in donation after cardio-circulatory death (DCD) started in the 1990s following the limited success of the transplant community to expand the donation after brain-death (DBD) organ supply and following the request of potential DCD families. Since then, DCD organ procurement and transplantation activities have rapidly expanded, particularly for non-vital organs, like kidneys. In liver transplantation (LT), DCD donors are a valuable organ source that helps to decrease the mortality rate on the waiting lists and to increase the availability of organs for transplantation despite a higher risk of early graft dysfunction, more frequent vascular and ischemia-type biliary lesions, higher rates of re-listing and re-transplantation and lower graft survival, which are obviously due to the inevitable warm ischemia occurring during the declaration of death and organ retrieval process. Experimental strategies intervening in both donors and recipients at different phases of the transplantation process have focused on the attenuation of ischemia-reperfusion injury and already gained encouraging results, and some of them have found their way from pre-clinical success into clinical reality. The future of DCD-LT is promising. Concerted efforts should concentrate on the identification of suitable donors (probably Maastricht category III DCD donors), better donor and recipient matching (high risk donors to low risk recipients), use of advanced organ preservation techniques (oxygenated hypothermic machine perfusion, normothermic machine perfusion, venous systemic oxygen persufflation), and pharmacological modulation (probably a multi-factorial biologic modulation strategy) so that DCD liver allografts could be safely utilized and attain equivalent results as DBD-LT.

The role of normothermic extracorporeal perfusion in minimizing ischemia reperfusion injury

The primary objective of organ preservation is to deliver a viable graft with minimal risk of impaired postoperative graft function. In current clinical practice, preservation of transplanted organs is based on hypothermia. Organs are flushed and stored using specific preservation solutions to reduce cellular metabolism and prevent cell swelling. However, the ongoing organ donor shortage and consequent expansion of donor criteria to include the use of grafts that would once have been discarded as unsuitable have underlined the need for a technique that prevents any further damage during the preservation period. The principle of normothermic machine perfusion preservation is the maintenance of cellular metabolism in a physiological environment throughout the preservation period. Normothermic preservation, at least in theory, thereby overcomes the 3 major weaknesses inherent in traditional static cold storage by (1) avoiding ischemia/reperfusion injury, (2) avoiding cold injury, and (3) allowing viability assessment. Furthermore, normothermic machine perfusion might transpire to be the ideal vehicle to deliver other therapeutic interventions during preservation to modulate and optimize the graft before transplantation. By restoring function in marginal donor organs and enabling the clinician to appraise its viability, the donor pool might be greatly expanded.

Bile UPLC-MS fingerprinting and bile acid fluxes during human liver transplantation

Bile flow restoration is a crucial step in the recovery process post transplantation of the liver. Here, metabolic trajectories based on changes in bile secretion - a known marker of functionality - have been utilised as an approach for discovering bile fluxes during transplantation. A total of ten liver transplants were monitored and from these 68 bile samples from both donors and recipients were collected and analysed using ultra-performance LC-MS in combination with multivariate statistical analysis. Based on the principal component scores constructed from the total bile fingerprint, differentiation of the bile acid concentrations before and after transplantation was detected. A trend was also observed, by constructing metabolic trajectories, whereby the post-transplant profiles approached the position of pre-transplant profiles within 30-60 min of the restoration of bile secretion function. The ten major conjugated bile acid salts were measured and a significant increase in concentrations of taurocholic acid and taurochenodeoxycholic acid were seen after transplantation. In addition, the ratios of secondary bile acids detected in gall bladder and hepatic bile were measured before and after transplantation. This study suggests that bile acid ratios in the donor liver at the pre-transplant and post-transplant stage may be important and that profiling of secreted bile after transplantation may aid clinical assessment and progress post-transplantation.

Ex-vivo normothermic liver perfusion: an update

PURPOSE OF REVIEW

There is increasing disparity between the supply of acceptable donor organs and the number of potential transplant recipients. The shortage of organs for transplantation demands optimal utilization of a wider spectrum of donor organs, including nonheart-beating and other extended criteria donors. In the case of the liver, a substantial number of organs are discarded because of a risk of primary nonfunction.

RECENT FINDINGS

For many years hypothermic preservation has been the universal standard for organ preservation. Although limited in terms of the duration of preservation it has had the major advantages of simplicity, portability and affordability. Organ preservation by normothermic machine perfusion has repeatedly proven superiority over static cold storage in experimental settings. However, it is complex and costly and its place in clinical transplantation has not yet been established. In liver preservation normothermic perfusion provides the potential: (a) to preserve extended criteria grafts for long periods; (b) to assess the viability of these grafts during perfusion; and (c) to improve the condition of the grafts.

SUMMARY

Avoidance of cold ischaemic preservation damage and repair of injury sustained during warm ischaemia and organ procurement would potentially allow many livers from extended criteria donors to be transplanted reliably. The current challenges are, first to confirm the feasibility of the normothermic machine perfusion methodology in human livers and, second, to develop and introduce a functional device into the clinical arena.

Metabonomics: a useful tool for the future surgeon

BACKGROUND

In the past decade or so, a range of technologies have emerged that have shown promise in increasing our understanding of disease processes and progression. These advances are referred to as the "omics" technologies; genomics, transcriptomics, and proteomics. More recently, another "omics" approach has come to the fore: metabonomics, and this technology has the potential for significant clinical impact. Metabonomics refers to the analysis of the metabolome, that is, the metabolic profile of a system. The advantage of studying the metabolome is that the end points of biological events are elucidated.

RESULTS

Although still in its infancy, the metabonomics approach has shown immense promise in areas as diverse as toxicology studies to the discovery of biomarkers of disease. It has also been applied to studies of both renal and hepatic transplants. Metabolome analysis may be conducted on a variety of biological fluids and tissue types and may utilize a number of different technology platforms, mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy being the most popular. In this review, we cover the background to the evolution of metabonomics and its applications with particular emphasis on clinical applications.

CONCLUSIONS

We conclude with the suggestion that metabonomics offers a platform for further biomarker development, drug development, and in the field of medicine.

Fingerprinting of human bile during liver transplantation by capillary electrophoresis

Increasing rates of success in liver transplantation have increased the number of cases considered. However, liver post-transplant graft dysfunction of liver transplants (TXs) is not fully understood and by applying holistic approaches we can investigate metabolic change deriving from confounding factors such as liver fat content, ischaemia time, donor age, recipient's health, etc. Twenty-six hepatic bile samples taken from liver donors and recipients were retrieved from a total of six TXs, from these one recipient underwent post-graft dysfunction. CE was employed to fingerprint bile collected at 10 min increments in the donors and in the recipients. The electropherograms of these samples were aligned and normalised using correlation optimised warping algorithms and modelled with multivariate techniques. The resulting metabolic signatures were compared; in general donors and recipients showed distinct fingerprints and clustered separately. When a partial least square discriminant analysis (PLS-DA) model was constructed between donor and recipient's samples, a recipient of a 32 year old liver with normal steatosis, and shortest cold ischaemia time showed as the observation nearest to its donor observation, denoting minimal metabolic change. This study proposes CE fingerprinting of human bile as a promising technique to help unravel the complex metabolic pathways involved during transplantation.

The extent of vacuolation in non-heart-beating porcine donor liver grafts prior to transplantation predicts their viability

Livers exposed to prolonged warm ischemia (WI), such as those from non-heart-beating donors (NHBDs), are at higher risk of primary graft nonfunction (PNF). In a pig model of liver transplantation (LTx) from NHBDs, hepatocellular vacuolation, focal hepatocyte dropout, congestion, and sinusoidal dilatation appeared on biopsies taken after exposure to WI. In functioning grafts, vacuolation and sinusoidal dilatation were reversible after LTx, in contrast to PNF grafts. We studied whether the extent of these morphological signs and particularly vacuolation, present on pre-LTx biopsies, was associated with WI length and able to predict PNF, hepatocellular damage, and survival. Pre-LTx biopsies from pig livers exposed to incremental periods of WI were reviewed retrospectively. The extent of vacuolation was quantified blindly by a pathologist's semiquantitative score, validated by stereological point counting and digital image analysis, and then used to predict PNF and hepatocellular damage. On biopsies taken after WI, stereological point counting and digital analysis scoring contributed significantly in predicting PNF (P = 0.027 and P = 0.043, respectively) versus the pathologist's semiquantitative score (P = 0.058). Stereological point counting and digital image analysis predicted the extent of hepatocellular damage (P < 0.0001 and P = 0.001) versus the pathologist's semiquantitative score (P = 0.085). In conclusion, the extent of parenchymal vacuolation present on WI liver grafts reflects the severity of hepatocellular damage and predicts pig liver graft viability before LTx. Further studies are now warranted to evaluate whether these anoxic changes that are associated with liver graft viability in pigs also apply to human NHBD liver biopsies.

Ischemic cholangiopathy after liver transplantation from controlled non-heart-beating donors-a single-center experience

BACKGROUND

Previous reports have shown that livers from controlled non-heart-beating-donors (NHBD) are associated with higher rates of primary failure and ischemic cholangiopathy of orthotopic liver transplantation (OLT) as a complication of the prolonged warm ischemia.

METHODS

This retrospective review of activities from 1999 to 2006 examined donor characteristics of age, liver function tests, warm ischemic time before (1WITa) and after cardiac arrest (1WITb), cold ischemic time (CIT) and transplant results.

RESULTS

Eleven NHBD retrieved livers were transplanted from "ideal" donors except for one elderly donor (73 years). Of the 11 recipients, 3 developed biliary cholangiopathy (27%). There were no episodes of primary graft nonfunction, but one recipient displayed primary graft dysfunction. Two recipients died: one due to biliary complications with sepsis (long CIT >10 hours, fatty liver), and the other due to aspiration pneumonia and hypoxic brain damage with normal liver function. One recipient required retransplantation owing to ischemic cholangiopathy (1WITb 45 min) at 6 months after OLT with a good result. The other eight recipients are alive (observation period 72 to 14 months) including six with normal liver function, one with biopsy-proven biliary ischemia and one with recurrent primary sclerosing cholangitis without biliary ischemic changes on biopsy. Among 164 heart-beating donors recipients transplanted in the same period, biliary complications occurred in 27 patients (16%), of whom 12 were leaks and 15 anastomotic strictures.

CONCLUSION

NHBD were a good source for livers with reasonable early results. To avoid late complications especially ischemic cholangiopathy, caution is urged with the use of these organs as well as strict donor and ischemic time criteria.

Isolation of hepatocytes from livers from non-heart-beating donors for cell transplantation

One of the limitations to hepatocyte transplantation is the restricted availability of donor liver tissue. The aim of this study was to evaluate livers from non-heart-beating donors (NHBDs) as a source of hepatocytes for cell transplantation. A total of 20 livers/segments obtained from NHBD were perfused under good manufacturing practices using a standard collagenase digestion method. The donor liver median warm ischemia time was 15 minutes (range, 11-40 minutes), and cold ischemia time was 13 hours (range, 6-30 hours) prior to cell isolation. The cell viability of the hepatocytes obtained was 52% (1-81%), with a yield of 2.2 x 10(6)(0.2-29.7 x 10(6)) cells per gram of tissue. There was a significant negative correlation between hepatocyte viability and length of both warm ischemia (r = -0.544, P = 0.013) and cold ischemia (r = -0.510, P = 0.022). Preliminary experiments were performed on the viability testing of NHBD livers based on digestion of needle biopsies with collagenase and assessment of the hepatocytes produced. Two of the NHBD cell preparations, which had been cryopreserved, were used as part of a series of cell infusions for hepatocyte transplantation. A 3.5-yr-old girl with Crigler-Najjar syndrome type I received 9.7 x 10(8) NHBD hepatocytes (viability on thawing, 65%), and a 4-month-old boy with inherited clotting factor VII deficiency received 5.0 x 10(8) hepatocytes (viability, 57%). In conclusion, hepatocytes suitable for cell transplantation can be obtained from NHBD livers. Higher viability values may be obtained if both warm and cold ischemia times of donor liver can be reduced prior to processing.

24-h storage of pig livers in UW, HTK, hydroxyethyl starch, and saline solution: is microdialysis an appropriate method for the continuous graft monitoring during preservation?

Recent studies demonstrate the feasibility of microdialysis to monitor metabolism in ischemic livers. Whether these parameters correlate with markers of liver cell integrity in an experimental model using pig livers and different preservation solutions was an aim of this study. Pig livers were flushed with either 4 degrees C Histidine-Typtophan-Ketoglutarate solution (HTK) (Custodiol), University of Wisconsin solution (ViaSpan), and hydroxyethyl starch, or 12 degrees C saline solution. After 24-h storage, the livers were rinsed with saline to measure liver enzymes and lactate from the effluate. Utilizing microdialysis, intraparenchymal lactate, pyruvate, glucose, and glycerol was monitored. Tissue biopsies were taken for histological examinations. Cold preservation resulted in a decrease of metabolic activity measured by intrahepatic glucose, lactate, and pyruvate levels, as well as lactate in the effluate, independently of the solution used. Of particular interest, glycerol levels partially reflected the extent of hepatocellular damage and liver enzyme release. Glycerol levels partially discriminated preservation of different quality and were in accordance to histological findings and liver enzyme release. Lactate, pyruvate, and glucose levels were not appropriate as markers during cold storage. Whether or not glycerol monitoring could represent an additional and rational complementation to the current practice of macroscopic, microscopic and donor evaluation has to be clarified by further studies.

Organ donation and utilization in the United States, 2004

This article discusses issues directly related to the organ donation process, including donor consent, donor medical suitability, non-recovery of organs, organs recovered but not transplanted, expanded criteria donors (ECD), and donation after cardiac death (DCD). The findings and topics covered have important implications for how to evaluate and share best practices of organ donation as implemented by organ procurement organizations (OPOs) and major donor hospitals in the same donation service areas (DSAs). In 2002 and 2003, US hospitals referred more than one million deaths or imminent deaths to the OPOs of their DSA. Referrals increased by nearly 10% from 2002 to 2003 (1,022,280 to 1,121,392). Donor consents have increased by about 5% and the number of total deceased donors has risen from 6,187 to 6,455. Since multiple organs are recovered from most donors, this increase allowed more than 500 additional wait-listed candidates to receive an organ transplant than in the prior year. Non-traditional donor sources have experienced a large rate of increase; in 2003 the number of ECD kidney donors increased by 8% and the number of DCD donors increased by 43%, from 189 donors in year 2002 to 271 donors in 2003.

High-frequency ultrasound for monitoring changes in liver tissue during preservation

Currently the only method to assess liver preservation injury is based on liver appearance and donor medical history. Previous work has shown that high-frequency ultrasound could detect ischemic cell death due to changes in cell morphology. In this study, we use high-frequency ultrasound integrated backscatter to assess liver damage in experimental models of liver ischemia. Ultimately, our goal is to predict organ suitability for transplantation using high-frequency imaging and spectral analysis techniques. To examine the effects of liver ischemia at different temperatures, livers from Wistar rats were surgically excised, immersed in phosphate buffer saline and stored at 4 and 20 degrees C for 24 h. To mimic organ preservation, livers were excised, flushed with University of Wisconsin (UW) solution and stored at 4 degrees C for 24 h. Preservation injury was simulated by either not flushing livers with UW solution or, before scanning, allowing livers to reach room temperature. Ultrasound images and corresponding radiofrequency data were collected over the ischemic period. No significant increase in integrated backscatter (approximately 2.5 dBr) was measured for the livers prepared using standard preservation conditions. For all other ischemia models, the integrated backscatter increased by 4-9 dBr demonstrating kinetics dependent on storage conditions. The results provide a possible framework for using high-frequency imaging to non-invasively assess liver preservation injury.

Liver transplantation from non-heart-beating donors: current status and future prospects

Liver transplantation is the treatment of choice for many patients with acute and chronic liver failure, but its application is limited by a shortage of donor organs. Donor organ shortage is the principal cause of increasing waiting lists, and a number of patients die while awaiting transplantation. Non-heart-beating donor (NHBD) livers are a potential means of expanding the donor pool. This is not a new concept. Prior to the recognition of brainstem death, organs were retrieved from deceased donors only after cardiac arrest. Given the preservation techniques available at that time, this restricted the use of extrarenal organs for transplantation. In conclusion, after establishment of brain death criteria, deceased donor organs were almost exclusively from heart-beating donors (HBDs). To increase organ availability, there is now a resurgence of interest in NHBD liver transplantation. This review explores the basis for this and considers some of the published results.

Bile acids analysis: a tool to assess graft function in human liver transplantation

The expanding use of "sub-optimal" grafts due to donor organ shortage increases the importance of accurate graft assessment before liver transplantation. Bile secretion is an early sign of recovering hepatic function post-transplant. The role of bile acid analysis in assessing graft function before and immediately after liver transplantation has been investigated. Two hundred and sixteen samples of hepatic bile were collected from 35 donors and 13 recipients. Clinical data, bile flow, total bile acid concentration, apparent choleretic activity and bile acid composition were assessed. Sub-optimal donor livers showed a low apparent choleretic activity and a different bile acid composition when compared to normal grafts. In recipients, the pattern of recovery of bile secretion immediately after reperfusion was a useful predictor of graft function. This study characterises bile acid secretion of liver grafts and remarks the potential value of bile acid analysis to assess donor liver quality and early post-transplant graft function.

Liver and kidney preservation by perfusion

The clinical boundaries of transplantation have been set in an era of simple cold storage. Research in organ preservation has led to the development of flush solutions that buffer the harsh molecular conditions which develop during ischaemia, and provide stored organs that are fit to sustain life after transplantation. Although simple and efficient, this method might be reaching its limit with respect to the duration, preservation, and the quality of organs that can be preserved. In addition, flush preservation does not allow for adequate viability assessment. There is good evidence that preservation times will be extended by the provision of continuous cellular substrate. Stimulation of in-vivo conditions by ex-vivo perfusion could also mean that marginal organs will be salvaged for transplantation. Perfusion will also allow for assessing the viability of organs before transplantation in a continuous fashion. The cumulative effect of these benefits would include expansion of the donor pool, less risk of primary non-function, and extension of the safe preservation period. Use of non-heart-beating donors, international organ sharing, and precise calculation of the risk of primary organ failure could become standard.

Proton nuclear magnetic resonance analysis of hepatic bile from donors and recipients in human liver transplantation

The current shortage of donor organs in liver transplantation has led experienced transplant centers to use more "marginal" grafts. The development of a reliable technique of bile collection gives access to hepatic bile from donors and recipients for bile analysis to characterize the grafts. Proton nuclear magnetic resonance analysis has been applied to the study of bile for more than 30 years, showing encouraging results. This is the first study where proton nuclear magnetic resonance analysis has been applied to hepatic bile from selected liver grafts to evaluate its potential role in graft assessment. Hepatic bile was collected from eight liver donors (four with normal and four with steatotic grafts) during organ retrieval and four transplant recipients (two with good early graft function and two with primary dysfunction) immediately after graft reperfusion. A Varian Unity+ NMR spectrometer, operating at 11.7 Tesla (500 MHz for 1H), was used to obtain the proton nuclear magnetic resonance spectra. The results showed that the hepatic bile from steatotic grafts collected before transplantation had more intense phosphatidylcholine head group resonance than bile from normal grafts. It also showed slower clearance of University of Wisconsin solution in grafts with subsequent primary graft dysfunction, suggesting a slower recovery of bile secretion. These preliminary findings suggest that proton nuclear magnetic resonance analysis might help to differentiate the characteristics of bile acids and biliary lipids from normal and steatotic grafts. The monitoring of the resonance signal of University of Wisconsin solution washout, bile acid, and biliary lipid secretion may help to predict the development of primary graft dysfunction and avoid the need for retransplantation.