Comparison of intracellular flushing and cold storage to machine perfusion for human kidney preservation

Machine perfusion in abdominal organ transplantation: Current use in the Netherlands

Scarcity of donor organs and the increment in patients awaiting a transplant increased the use of organs from expanded criteria donors or donation after circulatory death. Due to the suboptimal outcomes of these donor organs, there is an increased interest in better preservation methods, such as ex vivo machine perfusion or abdominal regional perfusion to improve outcomes. This state-of-the-art review aims to discuss the available types of perfusion techniques, its potential benefits and the available evidence in kidney, liver and pancreas transplantation. Additionally, translational steps from animal models towards clinical studies will be described, as well as its application to clinical practice, with the focus on the Netherlands. Despite the lack of evidence from randomized controlled trials, currently available data suggest especially beneficial effects of normothermic regional perfusion on biliary complications and ischemic cholangiopathy after liver transplantation. For ex vivo machine perfusion in kidney transplantation, hypothermic machine perfusion has proven to be beneficial over static cold storage in a randomized controlled trial, while normothermic machine perfusion is currently under investigation. For ex vivo machine perfusion in liver transplantation, normothermic machine perfusion has proven to reduce discard rates and early allograft dysfunction. In response to clinical studies, hypothermic machine perfusion for deceased donor kidneys has already been implemented as standard of care in the Netherlands.

Maximizing kidneys for transplantation using machine perfusion: from the past to the future: A comprehensive systematic review and meta-analysis

BACKGROUND

The two main options for renal allograft preservation are static cold storage (CS) and machine perfusion (MP). There has been considerably increased interest in MP preservation of kidneys, however conflicting evidence regarding its efficacy and associated costs have impacted its scale of clinical uptake. Additionally, there is no clear consensus regarding oxygenation, and hypo- or normothermia, in conjunction with MP, and its mechanisms of action are also debated. The primary aims of this article were to elucidate the benefits of MP preservation with and without oxygenation, and/or under normothermic conditions, when compared with CS prior to deceased donor kidney transplantation.

METHODS

Clinical (observational studies and prospective trials) and animal (experimental) articles exploring the use of renal MP were assessed (EMBASE, Medline, and Cochrane databases). Meta-analyses were conducted for the comparisons between hypothermic MP (hypothermic machine perfusion [HMP]) and CS (human studies) and normothermic MP (warm (normothermic) perfusion [WP]) compared with CS or HMP (animal studies). The primary outcome was allograft function. Secondary outcomes included graft and patient survival, acute rejection and parameters of tubular, glomerular and endothelial function. Subgroup analyses were conducted in expanded criteria (ECD) and donation after circulatory (DCD) death donors.

RESULTS

A total of 101 studies (63 human and 38 animal) were included. There was a lower rate of delayed graft function in recipients with HMP donor grafts compared with CS kidneys (RR 0.77; 95% CI 0.69-0.87). Primary nonfunction (PNF) was reduced in ECD kidneys preserved by HMP (RR 0.28; 95% CI 0.09-0.89). Renal function in animal studies was significantly better in WP kidneys compared with both HMP (standardized mean difference [SMD] of peak creatinine 1.66; 95% CI 3.19 to 0.14) and CS (SMD of peak creatinine 1.72; 95% CI 3.09 to 0.34). MP improves renal preservation through the better maintenance of tubular, glomerular, and endothelial function and integrity.

CONCLUSIONS

HMP improves short-term outcomes after renal transplantation, with a less clear effect in the longer-term. There is considerable room for modification of the process to assess whether superior outcomes can be achieved through oxygenation, perfusion fluid manipulation, and alteration of perfusion temperature. In particular, correlative experimental (animal) data provides strong support for more clinical trials investigating normothermic MP.

Does machine perfusion decrease ischemia reperfusion injury?

In 1990's, use of machine perfusion for organ preservation has been abandoned because of improvement of preservation solutions, efficient without perfusion, easy to use and cheaper. Since the last 15 years, a renewed interest for machine perfusion emerged based on studies performed on preclinical model and seems to make consensus in case of expanded criteria donors or deceased after cardiac death donations. We present relevant studies highlighted the efficiency of preservation with hypothermic machine perfusion compared to static cold storage. Machines for organ preservation being in constant evolution, we also summarized recent developments included direct oxygenation of the perfusat. Machine perfusion technology also enables organ reconditioning during the last hours of preservation through a short period of perfusion on hypothermia, subnormothermia or normothermia. We present significant or low advantages for machine perfusion against ischemia reperfusion injuries regarding at least one primary parameter: risk of DFG, organ function or graft survival.

Pulsatile machine perfusion vs. cold storage of kidneys for transplantation: a rapid and systematic review

OBJECTIVE

To identify and prioritize key areas for further research in kidney preservation systems.

MATERIALS AND METHODS

We conducted a systematic review and meta-analysis of the effectiveness of machine perfusion and cold storage techniques in reducing delayed graft function (DGF) and improving graft survival in recipients of kidneys from beating and non-heart-beating donors. Literature quantifying the link between DGF and graft survival was used to evaluate the potential long-term impact of machine perfusion and cold storage systems. Cox proportional hazards modelling was used to predict graft survival and graft years gained over 10 yr. Monte Carlo sensitivity analysis was conducted to evaluate stochastic uncertainties within the model.

RESULTS

Machine perfusion leads to a relative risk of DGF of approximately 80% (67%, 96%) compared with cold storage, although the evidence base is limited in quality and study size. Direct evidence on graft survival at 1 yr demonstrates no statistically significant difference between machine perfusion and cold storage. Predictions based upon quantifying the link between DGF and graft survival suggest potential improvements of between 0 and 6% at 10 yr.

DISCUSSION

Studies of high methodological quality and sufficient size are required to determine whether machine preservation leads to reduce rates of DGF. Predicted impact on graft survival implies that direct evidence would require a large population followed up over a long period of time. Registry database analysis supported by validation of the link between DGF and graft survival may be preferable and more feasible than randomized controlled trials.

Nonheart-beating kidney donation: current practice and future developments

BACKGROUND

Nonheart-beating kidney donation (NHBD) is gaining acceptance as a method of donor pool expansion. However, a number of practitioners have concerns over rates of delayed graft function, acute rejection, and long-term graft survival. The ethical issues associated with NHBD are complex and may be a further disincentive. Tailored strategies for preservation, viability prediction, and immunosuppression for kidneys from this source have the potential to maximize the number of available organs. This review article presents the current practice of NHBD kidney transplantation, examines the results and draws comparisons with cadaveric kidneys, and explores some areas of potential development.

METHODS

A review of the current literature on NHBD kidney donation was performed.

RESULTS

The renewed interest in NHBD kidneys is driven by a continuing shortfall in available organs. Those centers involved in NHBD report an increase in kidney transplants of the order of 16% to 40% and there is no evidence that the financial costs are higher with NHBDs. The majority of experience comes from Maastricht category 2 NHBDs, where an estimation of warm time is possible. This is generally limited to 40 minutes. There are variations in the technique for kidney preservation prior to retrieval, but most centers use an aortic balloon catheter. Much work has looked at the ideal technique for kidney preservation prior to implantation. Evidence suggests that machine perfusion produces the best initial function rates, decreased use of adjuvant immunotherapy and fewer haemodialysis sessions than static cold storage.

CONCLUSION

Despite being associated with poorer initial graft function, the long-term allograft survival of NHBD kidneys does not differ from the results of transplantation from cadaveric kidneys. Further, serum creatinine levels are generally equivalent. Constant reassessment of the ethical issues is required for donation to be increased while respecting public concerns. Use of viability assessment and tailoring of immune suppression for NHBD kidneys may allow a further increase in donation from this source.

Improving the quality of kidneys from non-heart-beating donors, using streptokinase: an animal model

BACKGROUND

Non-heart-beating donors (NHBD) offer a promising potential to increase the cadaveric organ donor pool, especially for kidneys. However, almost half of NHBD kidneys are discarded after viability assessment. This wastage is costly in both human and monetary terms. Intravascular thrombosis at the time of donor death is an event leading to failure in the viability assessment. We have developed an animal model to investigate the effects of the addition of streptokinase to the in situ flush medium before transplant in an attempt to redress the situation.

METHODS

Two groups of eight healthy young Landrace Yorkshire white pigs were entered into the study. Both groups were subjected to approximately 70 min warm ischemia. Both groups received an intravascular flush with 4 L of Marshall's solution with heparin (1000 IU/L); one group of pigs also had streptokinase (1.5 MIU/L) added. After donor nephrectomy, all kidneys were machine perfused for 4 hr. Data on perfusion characteristics were taken and samples of kidney effluent were assayed for tissue damage biomarkers, glutathione S-transferase (GST) and alanine aminopeptidase (Ala-AP). Wedge sections of porcine kidneys were taken at the end of perfusion, for histological analysis.

RESULTS

Data on machine perfusion parameters (temperature, mean pressure index, resistance) indicate better cooling, lower resistance, and lower mean pressure index in the streptokinase-treated group of pigs. GST and Ala-AP levels were increased in the nonstreptokinase group perfusates. Histopathological analysis of porcine kidneys indicated more ischemic injury and tissue damage in the nonstreptokinase group.

CONCLUSION

The use of streptokinase in this porcine NHBD model conferred benefits to donor kidneys when assessed by machine perfusion. Markers of biochemical injury indicated that less renal tissue damage occurred with the incorporation of streptokinase in the in situ flush medium.

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.

Ten years of training community urologists and general surgeons to do cadaver kidney retrievals

We trained 82 community hospital cadaver kidney retrieval teams during a 10-year period ending June 30, 1987. During the last 5 years of that period the concept of multiple organ retrieval was introduced into the training sessions and 429 cadaver kidney grafts were retrieved. Of those kidneys 292 were transplanted at our hospital, and the function of 220 cadaver kidney grafts retrieved by the community hospital teams was compared to that of 72 retrieved by the transplant center retrieval team. Of the cadaver kidney transplants 114 were from multiple organ donors. There was no significant difference in 1-month serum creatinine nadir of surviving grafts (2.1 +/- 1.8 versus 1.9 +/- 1.7 mg. per dl.), 6-month serum creatinine level (1.7 +/- 0.8 versus 1.6 +/- 0.6 mg. per dl.), 12-month serum creatinine level (1.8 +/- 0.9 versus 1.6 +/- 0.6 mg. per dl.) and 5-year actuarial graft survival (44.8 +/- 4.1 versus 52.4 +/- 7.5%), with the community hospital data presented first. The delayed graft function rate was significantly higher in the recipients of cadaver kidney grafts retrieved by community hospital teams (54 versus 35%), which was reduced by the in situ flush technique. There was no significant difference in delayed graft function rate (48 versus 40%) for the 114 cadaver kidney transplants retrieved from multiple organ donors by either community hospital or transplant center teams. With continuing education and quality control, community hospital retrieval teams can provide kidneys satisfactory for transplantation, even when working with multiple organ retrieval teams.

Transplantation of a horseshoe kidney into 2 recipients

A horseshoe kidney was retrieved en bloc with the aorta and inferior vena cava, divided at the isthmus and transplanted into 2 recipients. This anomaly is not a contraindication to cadaver kidney donation.

Human kidney preservation using machine perfusion followed by intracellular electrolyte flushing

Transplant centers that do not have pulsatile machine perfusion capabilities are reluctant to accept kidneys from programs that do. Four human kidneys were retrieved by other centers, initially placed on pulsatile machine perfusion pumps for 13 to 28 hours, removed from the pumps, flushed with intracellular electrolyte solutions and cold-stored for 13 to 36 hours before transplantation at our institution. All recipients required dialysis during the first week after transplantation. The 1-month serum creatinine nadir was 2.2 plus or minus 1.1 mg. per dl., and all kidney grafts were functioning 3 months after transplantation. Pulsatile machine perfusion followed by ice-cold intracellular electrolyte flushing and simple cold storage can provide satisfactory renal function when the warm ischemia time is short.

Renal allograft acute tubular necrosis. II. A light and electron microscopic study of biopsies taken at procurement and after revascularization

The light and electron microscopic morphology of 57 cadaver renal allografts was assessed at the time of procurement and again after revascularization. Twenty-two kidneys (39%) did not function immediately after transplantation and 19 of these (86%) contained morphologic evidence of acute tubular necrosis (ATN) in the procurement biopsy. The morphology of the post-transplant biopsy was abnormal in all 22 kidneys with delayed function. There was a wide spectrum of morphologic change between the time of procurement and revascularization in all kidneys with normal function. These changes were mild in nature, were usually confined to proximal tubules, and were of unknown clinical significance. The morphology of kidneys that were damaged by the time of procurement was surprisingly different after storage with simple hypothermia (ice) than after storage with hypothermic pulsatile perfusion. The changes attributed to ice storage included endothelial swelling and vacuolation with obliteration and collapse of capillary lumens, fracture and splitting of peritubular basement membrane, and hyalinization of the renal interstitium. It was unknown whether these morphologic abnormalities were associated with delayed recovery of function of the injured kidneys.

Comparison of imported with locally retrieved kidneys preserved by intracellular electrolyte flushing followed by cold storage

Ice-cold intracellular electrolyte flushing followed by cold storage and economy air shipment is the cheapest method to share kidneys for transplantation. This study from 1 center compares 62 primary cadaver kidney grafts imported from other centers to 128 that were retrieved locally. Cold ischemia time was 36.4 plus or minus 8.6 hours (mean plus or minus standard deviation) in the imported group and 24.2 plus or minus 8.8 hours in the locally retrieved group. The significant increase in first week dialysis (71 versus 42 per cent) and 1-month serum creatinine nadirs (2.63 plus or minus 2.73 versus 1.78 plus or minus 1.04 mg./dl.) was explained by longer cold ischemia times in the imported kidney grafts. There were no significant differences between the 2 groups with respect to actuarial kidney graft survivals and serum creatinine levels at 1, 2 and 3 years. Intracellular electrolyte flushing followed by simple cold storage and air transportation provides kidney graft survivals and long-term kidney graft function at minimal expense when the kidneys are retrieved from beating-heart cadavers and have undergone minimal warm ischemia.

Effect of donor surgeon on first cadaver kidney transplant function

Community urologists and general surgeons were recruited into a cadaver kidney program in 1976. This study from 1 center compares 41 primary cadaver kidney grafts retrieved by community hospital retrieval teams to 60 primary cadaver kidney grafts retrieved by a center-based transplant team. Of the kidneys 100 were preserved with Collins' C2 flushing followed by simple cold storage and 1 was preserved with pulsatile machine perfusion. Cold storage time ranged from 9 to 44.5 hours in the community hospital kidney group and from 11 to 44 hours in the university hospital group. There was no significant difference between the 2 kidney retrieval teams with respect to 1) incidence of acute tubular necrosis, 2) 1-month serum creatinine nadir of surviving grafts, 3) 1 and 2-year serum creatinine levels and 4) actuarial graft survivals up to 5 years. Community hospital retrieval teams can provide kidneys as satisfactory for transplantation as a center-based transplant team and are a valuable resource for cadaver kidney transplant programs.