Machine perfusion and long-term kidney transplant recipient outcomes across allograft risk strata

Mechanical Preservation and Delayed Graft Function and Hospital Length of Stay as Deployed in the United States: Analysis of the Last Decade

BACKGROUND Mechanical preservation (MP) of deceased donor kidney transplants showed a 30% to 50% reduction in delayed graft function (DGF) as defined by dialysis in the first week, when compared with cold storage. DGF is associated with longer hospital stays and increased costs. In this study, we sought to understand the impact of MP on rates of DGF and length of hospital stays in a contemporary cohort of deceased donor kidney transplants in the United States. MATERIAL AND METHODS All single deceased donor kidney transplants performed between January 1, 2010, and September 2, 2020, were identified in the Scientific Registry of Transplant Recipients database. Donor kidneys were considered pumped if the transplant center received the kidney on the pump. RESULTS Multivariate logistic regression showed that MP had similar odds of reduction of DGF for all subsets of donors. The unadjusted rate of DGF for pumped brain-dead standard criteria donor (BDSCD) recipients was similar to that of donors stored on ice. The rate of DGF for expanded criteria donors (ECD) and donors after cardiac death (DCD) was lower in the recipients who received MP. The similar DGF rates in BDSCD donor recipients were due to longer cold ischemia times in MP kidneys. The lower DGF rates seen in ECD and DCD recipients of pumped kidneys did not translate into a shortened length of hospitalization after transplant. CONCLUSIONS As currently deployed, only DCD and ECD donor recipients of MP kidneys experienced a lower DGF rate. In all subsets of patients, MP did not appreciably shorten the hospital length of stay.

Predicting Long-term Outcomes in Deceased Donor Kidney Transplant Recipients Using Three Short-term Graft Characteristics

Key Points

Delayed graft function is not an ideal measure of graft function, yet is used to assess risk in kidney transplantation. We propose a model that combines it with two other measures of 90-day graft function to identify recipients at incremental risk of inferior long-term outcomes.

Background

Delayed graft function (DGF) in kidney transplant recipients is used to determine graft prognosis, make organ utilization decisions, and as an important end point in clinical trials. However, DGF is not an ideal measure of graft function. We aimed to develop and validate a model that provides incremental risk assessment for inferior patient and graft outcomes.

Methods

We included adult kidney-only deceased donor transplant recipients from 1996 to 2016. In addition to DGF, two short-term measures were used to assess risk: renal function recovery <100% (attaining half the donor's eGFR) and recipient's 90-day eGFR <30. Recipients were at no, low, moderate, or high risk if they met zero, one, two, or all criteria, respectively. Cox proportional hazard models were used to assess the independent relationship between exposure and death-censored graft failure (DCGF) and mortality.

Results

Of the 792 eligible recipients, 24.5% experienced DGF, 40.5% had renal function recovery <100%, and 6.9% had eGFR <30. Over a median follow-up of 7.3 years, the rate of DCGF was 18.7% and mortality was 25.1%. When compared with recipients at no risk, those at low, moderate, and high risk were noted to have an increase in risk of DCGF (adjusted hazard ratio [aHR], 1.53; 95% confidence interval [CI], 1.03 to 2.27; aHR, 2.84; 95% CI, 1.68 to 4.79; aHR, 15.46; 95% CI, 8.04 to 29.71) and mortality (aHR, 1.16; 95% CI, 0.84 to 1.58; aHR, 1.85; 95% CI, 1.13 to 3.07; aHR, 2.66; 95% CI, 1.19 to 5.97). When using a hierarchical approach, each additional exposure predicted the risk of DCGF better than DGF alone and 100 random bootstrap replications supported the internal validity of the risk model. In an external validation cohort deemed to be at lower risk of DCGF, similar nonsignificant trends were noted.

Conclusion

We propose a risk model that provides an incremental assessment of recipients at higher risk of adverse long-term outcomes than DGF alone. This can help advance the field of risk assessment in transplantation and inform therapeutic decision making in patients at the highest spectrum of inferior outcomes.

Early Effect of the Circular Model of Kidney Allocation in the United States

BACKGROUND

In March 2021, the United States implemented a new kidney allocation system (KAS250) for deceased donor kidney transplantation (DDKT), which eliminated the donation service area-based allocation and replaced it with a system on the basis of distance from donor hospital to transplant center within/outside a radius of 250 nautical miles. The effect of this policy on kidney discards and logistics is unknown.

METHODS

We examined discards, donor-recipient characteristics, cold ischemia time (CIT), and delayed graft function (DGF) during the first 9 months of KAS250 compared with a pre-KAS250 cohort from the preceding 2 years. Changes in discards and CIT after the onset of COVID-19 and the implementation of KAS250 were evaluated using an interrupted time-series model. Changes in allocation practices (biopsy, machine perfusion, and virtual cross-match) were also evaluated.

RESULTS

Post-KAS250 saw a two-fold increase in kidneys imported from nonlocal organ procurement organizations (OPO) and a higher proportion of recipients with calculated panel reactive antibody (cPRA) 81%-98% (12% versus 8%; P <0.001) and those with >5 years of pretransplant dialysis (35% versus 33%; P <0.001). CIT increased (mean 2 hours), including among local OPO kidneys. DGF was similar on adjusted analysis. Discards after KAS250 did not immediately change, but we observed a statistically significant increase over time that was independent of donor quality. Machine perfusion use decreased, whereas reliance on virtual cross-match increased, which was associated with shorter CIT.

CONCLUSIONS

Early trends after KAS250 show an increase in transplant access to patients with cPRA>80% and those with longer dialysis duration, but this was accompanied by an increase in CIT and a suggestion of worsening kidney discards.

Preoperative blood pressure and risk of delayed graft function in deceased donor kidney transplantation

BACKGROUND

In kidney transplantation, delayed graft function (DGF) is associated with increased morbidity and a higher risk of graft failure. Prior research suggests that chronic hypotension increases DGF risk, but the relationship of preoperative blood pressure to DGF is unclear.

METHODS

In this single center study of adult deceased donor kidney transplant recipients transplanted between 2015 and 2019, we evaluated the question of whether preoperative mean arterial pressure (MAP) affected DGF risk. Additionally, we investigated whether the risk of DGF was moderated by certain donor and recipient characteristics. For recipient characteristics associated with increased DGF risk and preoperative MAP, we performed a mediation analysis to estimate the proportion of DGF risk mediated through preoperative MAP.

RESULTS

Among 562 deceased donor kidney recipients, DGF risk decreased as preoperative MAP increased, with a 2% lower risk per 1 mm Hg increase in MAP. This increased risk was similar, with no statistically significant interaction effect between preoperative MAP and donor (donation after circulatory death) and recipient characteristics (diabetes, body mass index, and use of anti-hypertensive medications). Preoperative MAP was negativity correlated with recipient BMI and duration of pre transplant dialysis. On mediation analysis, MAP accounted for 12% and 16% of the DGF risk associated with recipient BMI and pre-transplant dialysis duration, respectively.

CONCLUSION

In deceased donor kidney transplantation, each 1 mm Hg increase in preoperative MAP was associated with 2% lower DGF risk. Preoperative MAP was influenced by recipient BMI and dialysis duration, and likely contributes to some of the high DGF risk from obesity and long dialysis vintage.

Beyond Graft Survivl: A National Cohort Study Quantifying the Impact of Increasing Kidney Donor Profile Index on Recipient Outcomes 1 Year Post-transplantation

Background.

The reporting of a locally validated kidney donor profile index (KDPI) began in Australia in 2016. Across diverse populations, KDPI has demonstrated utility in predicting allograft survival and function. A metric that incorporates both elements may provide a more comprehensive picture of suboptimal recipient outcomes.

Methods.

A retrospective cohort study of adult kidney transplant recipients in Australia (January 2009 to December 2014) was conducted. Conventional recipient outcomes and a composite measure of suboptimal outcome (1-y allograft failure or estimated glomerular filtration rate [eGFR] <30 mL/min) were evaluated across KDPI intervals (KDPI quintiles and 5-point increments in the KDPI 81–100 cohort). The impact of increasing KDPI on allograft function (1-y eGFR) and a suboptimal outcome was explored using multivariable regression models, adjusting for potential confounding factors.

Results.

In 2923 donor kidneys eligible for analysis, median KDPI was 54 (interquartile range [IQR], 31–77), and Kidney Donor Risk Index was 1.39 (IQR, 1.03–1.67). The median 1-y eGFR was 52.74 mL/min (IQR, 40.79–66.41 mL/min). Compared with the first quintile reference group, progressive reductions in eGFR were observed with increasing KDPI and were maximal in the fifth quintile (adjusted β-coefficient: −27.43 mL/min; 95% confidence interval, –29.44 to –25.42; P < 0.001). A suboptimal outcome was observed in 359 recipients (12.3%). The adjusted odds for this outcome increased across quintiles from a baseline of odds ratio of 1.00 (first quintile) to odds ratio of 11.68 (95% confidence interval, 6.33-21.54, P < 0.001) in the fifth quintile cohort.

Conclusions.

Increases in donor KDPI were associated with higher probabilities of a suboptimal outcome and poorer baseline allograft function, particularly in the KDPI > 80 cohort. These findings may inform pretransplant discussions with potential recipients of high-KDPI allografts.

Machine perfusion of kidney allografts affects early but not late graft function

BACKGROUND

Hypothermic machine perfusion (HMP) parameters are influenced by donor variables which further affect recipient outcome. Interplay between these parameters can help to predict kidney performance on pump and the long term outcome.

METHODS

All the kidneys transplanted at our center between May 2013 through November 2017 were included in the study. Donor and recipient data was obtained from internal database. Multiple logistic regression models with backward selection were used to determine significant donor and pump variables.

RESULTS

Donor BMI, KDPI, age and donor sex had a significant association with pump flow. Donor sex, donor type, KDPI and age had significant effect on RI. Diastolic pressure and KDPI were significantly associated with DGF. Duration on pump, KDPI, flow, donor creatinine and type of donor were significantly associated with day 5 creatinine. KDPI was significantly associated with Day 365 creatinine.

CONCLUSION

HMP effects early graft function while the long term function depends on donor parameters.

Kidney transplant outcome of expanded criteria donors after circulatory death

The increase in the number of patients on the kidney transplant waiting list has led to an attempt to increase the number of potential donors by incorporating candidates that previously would not have been considered optimal, including donors after cardiac death (DCD) and those with "expanded" criteria (ECD). Recipients of controlled DCD (cDCD) grafts suffer more delayed graft function (DGF), but have a long-term evolution comparable to those of brain-dead donors, which has allowed an increase in the number of cDCD transplants in different countries in recent years. In parallel, the use of cDCD with expanded criteria (cDCD/ECD) has increased in recent years in different countries, allowing the waiting list for kidney transplantation to be shortened. The use of these grafts, although associated with a higher frequency of DGF, offers similar or only slightly lower long-term graft survival than those of brain death donors with expanded criteria. Different studies have observed that cDCD/ECD graft recipients have worse kidney function than cDCD/standard and DBD/ECD. Mortality associated with cDCD/ECD graft transplantation mostly relates to the recipient age. Patients who receive a cDCD/≥60 graft have better survival than those who continue on the waiting list, although this fact has not been demonstrated in recipients of cDCD/>65 years. The use of this type of organ should be accompanied by the optimization of surgical times and the shortest possible cold ischemia.

Advances in Hypothermic and Normothermic Perfusion in Kidney Transplantation

Hypothermic and normothermic machine perfusion in kidney transplantation are purported to exert a beneficial effect on post-transplant outcomes compared to the traditionally used method of static cold storage. Kidney perfusion techniques provide a window for organ reconditioning and quality assessment. However, how best to deliver these preservation methods or improve organ quality has not yet been conclusively defined. This review summarises the promising advances in machine perfusion science in recent years, which have the potential to further improve early graft function and prolong graft survival.

Early Graft Loss Following Transplantation From Expanded Criteria Donors

Background

Expanded criteria donor (ECD) kidneys are associated with higher graft loss rates than standard criteria donor kidneys. We sought to determine factors associated with early graft loss and their discrimination ability for this outcome compared with kidney donor risk index.

Methods

Data were extracted from the Australia and New Zealand Dialysis and Transplant Registry (ANZDATA) for ECD transplants between 1997 and 2014. The primary outcome was early graft loss (all-cause graft loss within 3 y of transplantation). Death-censored graft loss was substituted as a sensitivity analysis. Era-adjusted odds ratios were calculated by multivariable logistic regression for donor, recipient, and transplant factors available at transplantation. Discrimination was assessed by c-statistic, with 95% confidence intervals (CIs) calculated by bootstrapping.

Results

Of 2152 ECD kidney transplants, early graft loss occurred in 406 (19%) and was associated with recipient diabetes, smoking, First Nations recipients, and oliguria. Of factors defining ECD (age, elevated terminal creatinine, hypertension, death from cerebrovascular accident), all but mode of death were associated with early graft loss. The multivariable model, including known donor, recipient, and transplant factors, was moderately good at predicting early graft loss (c-statistic 0.65; 95% CI, 0.62-0.68). Recipient factors (c-statistic 0.62; 95% CI, 0.59-0.65) performed equally well compared with donor factors (c-statistic 0.60; 95% CI, 0.57-0.64) or the kidney donor risk index (c-statistic 0.60; 95% CI, 0.56-0.63).

Conclusions

Early graft loss occurs in approximately one-fifth of ECD kidney transplants. The discriminatory value of commonly used recipient, donor, and transplant factors are approximately comparable and limited.

Kidney transplant outcome of expanded criteria donors after circulatory death

The increase in the number of patients on the kidney transplant waiting list has led to an attempt to increase the number of potential donors by incorporating candidates that previously would not have been considered optimal, including donors after cardiac death (DCD) and those with "expanded" criteria (ECD). Recipients of controlled DCD (cDCD) grafts suffer more delayed graft function (DGF), but have a long-term evolution comparable to those of brain-dead donors, which has allowed an increase in the number of cDCD transplants in different countries in recent years. In parallel, the use of cDCD with expanded criteria (cDCD/ECD) has increased in recent years in different countries, allowing the waiting list for kidney transplantation to be shortened. The use of these grafts, although associated with a higher frequency of DGF, offers similar or only slightly lower long-term graft survival than those of brain death donors with expanded criteria. Different studies have observed that cDCD/ECD graft recipients have worse kidney function than cDCD/standard and brain death/ECD. Mortality associated with cDCD/ECD graft transplantation mostly relates to the recipient age. Patients who receive a cDCD/≥60 graft have better survival than those who continue on the waiting list, although this fact has not been demonstrated in recipients of cDCD/>65 years. The use of this type of organ should be accompanied by the optimization of surgical times and the shortest possible cold ischemia.

Changing Trends in Liver Transplantation: Challenges and Solutions

Despite improvements in postliver transplant outcomes through refinements in perioperative management and surgical techniques, several changing trends in liver transplantation have presented challenges. Mortality on the waitlist remains high. In the United States, Europe, and the United Kingdom, there is an increasing need for liver transplantation, primarily as a result of increased incidence of nonalcoholic steatohepatitis-related cirrhosis and cancer indications. Meanwhile, donor suitability has decreased, as donors are often older and have more comorbidities. Despite a mismatch between organ need and availability, many organs are discarded. Notwithstanding this, many solutions have been developed to overcome these challenges. Innovative techniques in allograft preservation, viability assessment, and reconditioning have allowed the use of suboptimal organs with adequate results. Refinements in surgical procedures, including live donor liver transplantations, have increased the organ pool and are decreasing the time and mortality on the waitlist. Despite many challenges, a similar number of solutions and prospects are on the horizon. This review seeks to explore the changing trends and challenges in liver transplantation and highlight possible solutions and future directions.

The Impact of Hypothermic Pulsatile Machine Perfusion Versus Static Cold Storage: A Donor-Matched Paired Analysis in a Scenario of High Incidence of Delayed Kidney Graft Function

BACKGROUND The present study analyzed the impact of hypothermic pulsatile machine perfusion (MP) following a long period of static cold (SC) storage in the peculiar Brazilian scenario of high incidence of delayed graft function (DGF), despite good donor characteristics. MATERIAL AND METHODS A retrospective analysis, with a 1-year follow-up, of 206 recipients of donor-matched paired kidneys was performed. Of the 206 donor kidneys, 103 were maintained exclusively in static cold storage (SC group) and 103 were kept on machine perfusion after a period of SC preservation (MP group). All donors were brain dead. RESULTS Only 4.9% of the kidneys were from expanded-criteria donors. Static cold ischemia time (CIT) in the SC group was 20.8±4.1 hours vs. 15.8±6.2 hours in the MP group (P<0.001). Dynamic CIT in the MP group was 12.3±5.7 hours. MP significantly reduced DGF incidence (29.1% vs. 55.3%, P<0.001), and this effect was confirmed in multivariable analysis (OR, 1.115; 95% CI, 1.033-1.204, P=0.001). No differences were observed between the groups with regard to DGF duration, length of hospital stay, incidence of primary nonfunction and acute rejection, graft loss, death, or renal function. CONCLUSIONS In this Brazilian setting, MP following a long period of SC preservation was associated with reduced DGF incidence in comparison with SC storage without MP.

Effect of preservation solutions for static cold storage on kidney transplantation outcomes: A National Registry Study

This study aimed to evaluate how 5 preservation solutions for static cold storage affected kidney transplant outcomes. It included all first single kidney transplants during 2010-2014 from donations after brain death in the French national transplant registry, excluding preemptive transplants and transplants of kidneys preserved with a hypothermic perfusion machine. The effects of each preservation solution on delayed graft function (DGF) and 1-year transplant failure were evaluated with hierarchical multivariable logistic regression models. The study finally included 7640 transplanted kidneys: 3473 (45.5%) preserved with Institut Georges Lopez-1 solution (IGL-1), 773 (10.1%) with University of Wisconsin solution, 731 (9.6%) with Solution de Conservation des Organes et Tissus (SCOT, organ and tissue preservation solution), 2215 (29.0%) with Celsior, and 448 (5.9%) with histidine-tryptophan-ketoglutarate. Primary nonfunction rates did not differ by solution. After adjustment for donor, recipient, and transplant characteristics, the DGF risk was significantly lower with IGL-1 than with all other solutions (odds ratio [OR] 0.55, 95% confidence interval [CI] 0.48-0.64). Conversely, SCOT was associated with a DGF risk significantly higher than the other solutions (OR 2.69, 95% CI 2.21-3.27) and triple that of IGL-1 (OR 3.37, 95% CI 2.72-4.16). One year after transplantation, the transplant failure rate did not differ significantly by preservation solution. The difference between the groups for 1-year mean creatinine clearance was not clinically relevant.

Cold Pulsatile Machine Perfusion Versus Static Cold Storage for Kidneys Donated After Circulatory Death: A Multicenter Randomized Controlled Trial

BACKGROUND

The benefits of cold pulsatile machine perfusion (MP) for the storage and transportation of kidneys donated after circulatory death are disputed. We conducted a UK-based multicenter, randomized controlled trial to compare outcomes of kidneys stored with MP versus static cold storage (CS).

METHODS

Fifty-one pairs of kidneys donated after circulatory death were randomly allocated to receive static CS or cold pulsatile MP. The primary endpoint, delayed graft function, was analyzed by "intention-to-treat" evaluation.

RESULTS

There was no difference in the incidence of delayed graft function between CS and MP (32/51 (62.8%) and 30/51 (58.8%) P = 0.69, respectively), although the trial stopped early due to difficulty with recruitment. There was no difference in the incidence of acute rejection, or in graft or patient survival between the CS and MP groups. Median estimated glomerular filtration rate at 3 months following transplantation was significantly lower in the CS group compared with MP (CS 34 mL/min IQR 26-44 vs MP 45 mL/min IQR 36-60, P = 0.006), although there was no significant difference in estimated glomerular filtration rate between CS and MP at 12 months posttransplant.

CONCLUSIONS

This study is underpowered, which limits definitive conclusions about the use of MP, as an alternative to static CS. It did not demonstrate that the use of MP reduces the incidence of delayed graft function in donation after circulatory death kidney transplantation.

Delayed graft function and perfusion parameters of kidneys from uncontrolled donors after circulatory death

Better preservation and evaluation of kidneys from donors after circulatory death serve to increase the number of kidneys available for transplantation and hypothermic machine perfusion has been shown to decrease ischemia reperfusion injury and delayed graft function. Data on relation between hemodynamic parameters during hypothermic machine perfusion and delayed graft function in kidneys from donors after circulatory death are so far scarce and not univocal. We aimed at assessing whether hemodynamic parameters measured during hypothermic machine perfusion (flow, mean perfusion pressure, and renal resistance) are associated with delayed graft function in 26 kidneys retrieved from uncontrolled donors after circulatory death. In our series, the incidence of delayed graft function was 57.7% (15/26). Recipients who developed delayed graft function had a longer warm ischemic time (p = 0.04). All hemodynamic parameters measured during hypothermic machine perfusion were comparable between recipients with delayed graft function and those without. According to our data, in kidneys from uncontrolled donors after circulatory death, a longer warm ischemic time (that is the overall time of no flow, as the sum of the no-flow and the no-touch period) is associated with delayed graft function. This finding underscores the pivotal role of ischemic injury in terms of absence of flow in affecting graft function. No association was detectable between hemodynamic parameters during hypothermic machine perfusion and the development of delayed graft function in our series.

Transplanting Marginal Organs in the Era of Modern Machine Perfusion and Advanced Organ Monitoring

Organ transplantation is undergoing profound changes. Contraindications for donation have been revised in order to better meet the organ demand. The use of lower-quality organs and organs with greater preoperative damage, including those from donation after cardiac death (DCD), has become an established routine but increases the risk of graft malfunction. This risk is further aggravated by ischemia and reperfusion injury (IRI) in the process of transplantation. These circumstances demand a preservation technology that ameliorates IRI and allows for assessment of viability and function prior to transplantation. Oxygenated hypothermic and normothermic machine perfusion (MP) have emerged as valid novel modalities for advanced organ preservation and conditioning. Ex vivo prolonged lung preservation has resulted in successful transplantation of high-risk donor lungs. Normothermic MP of hearts and livers has displayed safe (heart) and superior (liver) preservation in randomized controlled trials (RCT). Normothermic kidney preservation for 24 h was recently established. Early clinical outcomes beyond the market entry trials indicate bioenergetics reconditioning, improved preservation of structures subject to IRI, and significant prolongation of the preservation time. The monitoring of perfusion parameters, the biochemical investigation of preservation fluids, and the assessment of tissue viability and bioenergetics function now offer a comprehensive assessment of organ quality and function ex situ. Gene and protein expression profiling, investigation of passenger leukocytes, and advanced imaging may further enhance the understanding of the condition of an organ during MP. In addition, MP offers a platform for organ reconditioning and regeneration and hence catalyzes the clinical realization of tissue engineering. Organ modification may include immunological modification and the generation of chimeric organs. While these ideas are not conceptually new, MP now offers a platform for clinical realization. Defatting of steatotic livers, modulation of inflammation during preservation in lungs, vasodilatation of livers, and hepatitis C elimination have been successfully demonstrated in experimental and clinical trials. Targeted treatment of lesions and surgical treatment or graft modification have been attempted. In this review, we address the current state of MP and advanced organ monitoring and speculate about logical future steps and how this evolution of a novel technology can result in a medial revolution.

Examining the Increased Rates of Deceased Donor Kidney Nonutilization in Australia: What Has Changed?

BACKGROUND

From 2013, Australia has experienced a sustained increase in the proportion of deceased donor kidneys that are retrieved but not utilized for transplantation. We aimed to determine whether this could be explained by changes in donor characteristics over time.

METHODS

Registry data were used to examine predictors of kidney nonutilization over the period 2005-2017. Multilevel mixed effect logistic regression modeling and propensity score analysis were used to determine whether era of donation (2013-2017 versus 2005-2012) was an independent predictor of organ nonutilization after controlling for donor characteristics.

RESULTS

A total of 7810 kidneys were retrieved for the purpose of transplantation with 334 (4.3%) not utilized. The nonutilization rate was 5.8% in 2013-2017 compared to 2.7% in 2005-2012. Despite adjustment for donor characteristics, donation in the more recent era remained a significant predictor of kidney nonutilization (adjusted odds ratio, 1.98; 95% confidence interval, 1.54-2.54; P < 0.001). This finding was confirmed in the propensity score analysis.

CONCLUSIONS

Kidneys retrieved in Australia since 2013 were more likely not to be utilized for transplantation even after adjusting for changes in donor characteristics. The abrupt increase may be explained by increased clinical risk aversion, changes in unmeasured donor factors or logistical issues. Although nonutilization rates in Australia remain low by international standards, further clinical auditing of the reasons for offer decline may help to optimize resource utilization and maximize transplant opportunities.

Machine Perfusion and the Pancreas: Will It Increase the Donor Pool?

PURPOSE OF REVIEW

Pancreas transplantation enables complete patient independence from exogenous insulin administration and increases both patient survival and quality of life. Despite this, there has been a decline in pancreas transplantation for the past 20 years, influenced by changing donor demographics with more high-risk extended criteria (ECD) and donation after cardiac death (DCD) donors. This review discusses whether the advent of machine perfusion (MP), if extended to the pancreas, can increase the pool of suitable donor organs.

RECENT FINDINGS

Hypothermic and normothermic MP, as forms of preservation deemed superior to cold storage for high-risk kidney and liver donor organs, have opened the avenue for translation of this work into the pancreas. Recent experimental models of porcine and human ex-vivo pancreatic MP are promising. Applications of MP to the pancreas however need refinement-focusing on perfusion protocols and viability assessment tools. Emerging research shows pancreatic MP can potentially offer superior preservation capacity, the ability to both resuscitate and manipulate organs, and assess functional and metabolic organ viability. The future of MP will lie in organ assessment and resuscitation after retrieval, where ultimately organs initially considered high risk and unsuitable for transplantation will be optimised and transformed, making them then available for clinical use, thus increasing the pool of suitably viable pancreata for transplantation.

Evaluation of outcomes in renal transplantation with hypothermic machine perfusion for the preservation of kidneys from expanded criteria donors

In 2012, an expert working group from the French Transplant Health Authority recommended the use of hypothermic machine perfusion (HMP) to improve kidney preservation and transplant outcomes from expanded criteria donors, deceased after brain death. This study compares HMP and cold storage (CS) effects on delayed graft function (DGF) and transplant outcomes. We identified 4,316 kidney transplants from expanded criteria donors (2011-2014) in France through the French Transplant Registry. DGF occurrence was analyzed with a logistic regression, excluding preemptive transplants. One-year graft failure was analyzed with a Cox regression. A subpopulation of 66 paired kidneys was identified: one preserved by HMP and the other by CS from the same donor. Kidneys preserved by HMP (801) vs CS (3515) were associated with more frequent recipient comorbidities and older donors and recipients. HMP had a protective effect against DGF (24% in HMP group and 38% in CS group, OR = 0.49 [0.40-0.60]). Results were similar in the paired kidneys (OR = 0.23 [0.04-0.57]). HMP use decreased risk for 1-year graft failure (HR = 0.77 [0.60-0.99]). Initial hospital stays were shorter in the HMP group (P < 0.001). Our results confirm the reduction in DGF occurrence among expanded criteria donors kidneys preserved by HMP.

Renal resistance thresholds during hypothermic machine perfusion and transplantation outcomes - a retrospective cohort study

Renal resistance (RR), of allografts undergoing hypothermic machine perfusion (HMP), is considered a measure of organ quality. We conducted a retrospective cohort study of adult deceased donor kidney transplant (KT) recipients whose grafts underwent HMP. Our aim was to evaluate whether RR is predictive of death-censored graft failure (DCGF). Of 274 KT eligible for analysis, 59% were from expanded criteria donor. RR was modeled as a categorical variable, using a previously identified terminal threshold of 0.4, and 0.2 mmHg/ml/min (median in our cohort). Hazard ratios (HR) of DCGF were 3.23 [95% confidence interval (CI): 1.12-9.34, P = 0.03] and 2.67 [95% CI: 1.14-6.31, P = 0.02] in univariable models, and 2.67 [95% CI: 0.91-7.86, P = 0.07] and 2.42 [95% CI: 1.02-5.72, P = 0.04] in multivariable models, when RR threshold was 0.4 and 0.2, respectively. Increasing risk of DCGF was observed when RR over the course of HMP was modeled using mixed linear regression models: HR of 1.31 [95% CI: 1.07-1.59, P < 0.01] and 1.25 [95% CI: 1.00-1.55, P = 0.05], in univariable and multivariable models, respectively. This suggests that RR during HMP is a predictor of long-term KT outcomes. Prospective studies are needed to assess the survival benefit of patients receiving KT with higher RR in comparison with staying wait-listed.