Hypothermic machine perfusion is superior to static cold storage in deceased donor kidney transplantation: A meta-analysis

A Transplant-Inclusive Value-Based Kidney Care Payment Model

In the United States, kidney care payment models are migrating toward value-based care (VBC) models incentivizing quality of care at lower cost. Current kidney VBC models will continue through 2026. We propose a future transplant-inclusive VBC (TIVBC) model designed to supplement current models focusing on patients with advanced chronic kidney disease (CKD) and end-stage kidney disease (ESKD). The proposed TIVBC is structured as an episode-of-care model with risk-based reimbursement for "referral/evaluation/waitlisting" (REW, referencing kidney transplantation), "primary hospitalization to 180 days posttransplant," and "long-term graft survival." Challenges around organ acquisition costs, adjustments to quality metrics, and potential criticisms of the proposed model are discussed. We propose next steps in risk-adjustment and cost-prediction to develop as an end-to-end, TIVBC model.

Perfusion Techniques in Kidney Allograft Preservation to Reduce Ischemic Reperfusion Injury: A Systematic Review and Meta-Analysis

The limited supply and rising demand for kidney transplantation has led to the use of allografts more susceptible to ischemic reperfusion injury (IRI) and oxidative stress to expand the donor pool. Organ preservation and procurement techniques, such as machine perfusion (MP) and normothermic regional perfusion (NRP), have been developed to preserve allograft function, though their long-term outcomes have been more challenging to investigate. We performed a systematic review and meta-analysis to examine the benefits of MP and NRP compared to traditional preservation techniques. PubMed (MEDLINE), Embase, Cochrane, and Scopus databases were queried, and of 13,794 articles identified, 54 manuscripts were included (n = 41 MP; n = 13 NRP). MP decreased the rates of 12-month graft failure (OR 0.67; 95%CI 0.55, 0.80) and other perioperative outcomes such as delayed graft function (OR 0.65; 95%CI 0.54, 0.79), primary nonfunction (OR 0.63; 95%CI 0.44, 0.90), and hospital length of stay (15.5 days vs. 18.4 days) compared to static cold storage. NRP reduced the rates of acute rejection (OR 0.48; 95%CI 0.35, 0.67) compared to in situ perfusion. Overall, MP and NRP are effective techniques to mitigate IRI and play an important role in safely expanding the donor pool to satisfy the increasing demands of kidney transplantation.

Rescue Allocation Modes in Eurotransplant Kidney Transplantation: Recipient Oriented Extended Allocation Versus Competitive Rescue Allocation-A Retrospective Multicenter Outcome Analysis

BACKGROUND

Whenever the kidney standard allocation (SA) algorithms according to the Eurotransplant (ET) Kidney Allocation System or the Eurotransplant Senior Program fail, rescue allocation (RA) is initiated. There are 2 procedurally different modes of RA: recipient oriented extended allocation (REAL) and competitive rescue allocation (CRA). The objective of this study was to evaluate the association of patient survival and graft failure with RA mode and whether or not it varied across the different ET countries.

METHODS

The ET database was retrospectively analyzed for donor and recipient clinical and demographic characteristics in association with graft outcomes of deceased donor renal transplantation (DDRT) across all ET countries and centers from 2014 to 2021 using Cox proportional hazards methods.

RESULTS

Seventeen thousand six hundred seventy-nine renal transplantations were included (SA 15 658 [89%], REAL 860 [4.9%], and CRA 1161 [6.6%]). In CRA, donors were older, cold ischemia times were longer, and HLA matches were worse in comparison with REAL and especially SA. Multivariable analyses showed comparable graft and recipient survival between SA and REAL; however, CRA was associated with shorter graft survival. Germany performed 76% of all DDRTs after REAL and CRA and the latter mode reduced waiting times by up to 2.9 y.

CONCLUSIONS

REAL and CRA are used differently in the ET countries according to national donor rates. Both RA schemes optimize graft utilization, lead to acceptable outcomes, and help to stabilize national DDRT programs, especially in Germany.

Can We Predict Kidney Graft Function and Graft Survival Using Hypothermic Machine Perfusion Parameters From Donors After Circulatory Death?

Background

Hypothermic machine perfusion (HMP) reduces renal injury in donation after circulatory death donors with a high Kidney Donor Profile Index (KDPI). This study aims to characterize the correlation between KDPI, HMP parameters, and donor vitals during the withdrawal period in predicting short- and long-term graft outcomes.

Methods

ANOVA with Tukey's honestly significant difference tests compared the relationship between average flow, average resistance, peak resistance, flow slope, and resistance slope on day 30, 1-y, and 3-y eGFR, and days of delayed graft function. Graft and recipient survival rates were assessed using Kaplan-Meier analysis.

Results

The data for 72 grafts were suitable for analysis. Kidneys with KDPI >50% had a significantly higher day 30, and 1-y posttransplant eGFR, if HMP average flow was >150 mL/min, or the average resistance was <0.15 mm Hg/mL/min, compared with kidneys with also KDPI >50% but had not achieved the same pump parameters. There were no significant differences in the Kaplan-Meier analysis, considering recipient or graft survival, regardless of the KPDI score with 3- or 5-y outcomes.

Conclusions

Use of average resistance and average flow from a HMP, in conjunction with KDPI, may be predictive of the short- and long-term function of donation after circulatory death kidney transplants.

Enzymatic conversion of human blood group A kidneys to universal blood group O

ABO blood group compatibility restrictions present the first barrier to donor-recipient matching in kidney transplantation. Here, we present the use of two enzymes, FpGalNAc deacetylase and FpGalactosaminidase, from the bacterium Flavonifractor plautii to enzymatically convert blood group A antigens from the renal vasculature of human kidneys to 'universal' O-type. Using normothermic machine perfusion (NMP) and hypothermic machine perfusion (HMP) strategies, we demonstrate blood group A antigen loss of approximately 80% in as little as 2 h NMP and HMP. Furthermore, we show that treated kidneys do not bind circulating anti-A antibodies in an ex vivo model of ABO-incompatible transplantation and do not activate the classical complement pathway. This strategy presents a solution to the donor organ shortage crisis with the potential for direct clinical translation to reduce waiting times for patients with end stage renal disease.

The Effect of Perfusate Temperature on Delayed Graft Function in Deceased Donor Renal Transplantation

Introduction: Renal allograft hypothermic machine perfusion results in a decreased incidence of delayed graft function compared with static cold storage. Ensuring perfusate temperatures remain within the target range of 4-10 °C may impact delayed graft function rates. Project Aims: To identify whether this target was achieved and, if not, whether higher perfusate temperature was associated with delayed graft function. Design: In this retrospective cohort study, transplanted grafts from deceased donors placed on hypothermic machine perfusion pump from June 2019 to August 2020 were analyzed. Measurements were recovered after 5, 15, 60, and 180 min of perfusion. Univariable and multivariable analyses were performed to identify predictors of delayed graft function. Results: A total of 113 grafts from 94 donors were analyzed. Of these, 21 (19%) developed delayed graft function. On univariable logistic regression, variables associated with delayed graft function included older donor age (OR 1.08, P = .002), higher Kidney Donor Profile Index score (OR 1.03, P = .024), and higher 5-min perfusate temperature (T5 min; OR 1.49, P = .014). A higher T5 min was also associated with delayed graft function in multivariable logistic regression models (OR 1.58, P = .005; OR 1.37, P = .08). Grafts with T5 min >10 °C were more likely to experience delayed graft function than those with T5 min <10 °C (OR 4.5, P = .006). Conclusion: Higher early perfusate temperature was an independent predictor of delayed graft function and may be due to inadequate cooling of the circuit prior to placing grafts on pump. Quality improvement initiatives targeting early perfusate temperatures of ≤10 °C may reduce delayed graft function incidence.

Preventing Rejection of the Kidney Transplant

With increasing knowledge of immunologic factors and with the advent of potent immunosuppressive agents, the last several decades have seen significantly improved kidney allograft survival. However, despite overall improved short to medium-term allograft survival, long-term allograft outcomes remain unsatisfactory. A large body of literature implicates acute and chronic rejection as independent risk factors for graft loss. In this article, we review measures taken at various stages in the kidney transplant process to minimize the risk of rejection. In the pre-transplant phase, it is imperative to minimize the risk of sensitization, aim for better HLA matching including eplet matching and use desensitization in carefully selected high-risk patients. The peri-transplant phase involves strategies to minimize cold ischemia times, individualize induction immunosuppression and make all efforts for better HLA matching. In the post-transplant phase, the focus should move towards individualizing maintenance immunosuppression and using innovative strategies to increase compliance. Acute rejection episodes are risk factors for significant graft injury and development of chronic rejection thus one should strive for early detection and aggressive treatment. Monitoring for DSA development, especially in high-risk populations, should be made part of transplant follow-up protocols. A host of new biomarkers are now commercially available, and these should be used for early detection of rejection, immunosuppression modulation, prevention of unnecessary biopsies and monitoring response to rejection treatment. There is a strong push needed for the development of new drugs, especially for the management of chronic or resistant rejections, to prolong graft survival. Prevention of rejection is key for the longevity of kidney allografts. This requires a multipronged approach and significant effort on the part of the recipients and transplant centers.

Past, Current, and Future Perspectives on Transplanting Acute Kidney Injury Kidneys

(1) Background: Acute kidney injury (AKI) kidneys have high non-utilization rates due to concerns regarding unfavorable outcomes. In this paper, we aimed to review the past, present, and future opinions on AKI kidneys. (2) Methods: A PubMed search was conducted for topics relevant to AKI kidney transplantation. (3) Results: Current short- and long-term data on AKI kidneys have demonstrated good outcomes including favorable graft function and survival. The role of procurement biopsies is controversial, but they have been shown to be beneficial in AKI kidneys by allowing clinicians to differentiate between reversible tubular injury and irreversible cortical necrosis. Machine perfusion has also been applied to AKI kidneys and has been shown to reduce delayed graft function (DGF). The incidence of DGF increases with AKI severity and its management can be challenging. Strategies employed to counteract this have included early initiation of dialysis after kidney transplantation, early targeting of adequate immunosuppression levels to minimize rejection risk, and establishment of outpatient dialysis. (4) Conclusions: Despite good outcomes, there continue to be barriers that impact AKI kidney utilization. Successful strategies have included use of procurement biopsies or machine perfusion and expectant management of DGF. With increasing experience, better use of AKI kidneys can result in additional opportunities to expand the donor pool.

The role of flavin mononucleotide (FMN) as a potentially clinically relevant biomarker to predict the quality of kidney grafts during hypothermic (oxygenated) machine perfusion

Hypothermic machine perfusion (HMP) provides preservation superior to cold storage and may allow for organ assessment prior to transplantation. Since flavin mononucleotide (FMN) in perfusate has been proposed as a biomarker of organ quality during HMP of donor livers, the aim of this study was to validate FMN as a biomarker for organ quality in the context of HMP preserved kidneys. Perfusate samples (n = 422) from the paired randomised controlled COPE-COMPARE-trial, comparing HMP with oxygenation (HMPO2) versus standard HMP in kidneys, were used. Fluorescence intensity (FI) was assessed using fluorescence spectroscopy (excitation 450nm; emission 500-600nm) and validated by fluorospectrophotometer and targeted liquid chromatography mass spectrometry (LC-MS/MS). Fluorescence intensity (FI)(ex450;em500-600) increased over time during machine perfusion in both groups (p<0.0001). This increase was similar for both groups (p = 0.83). No correlation, however, was found between FI(ex450;em500-600) and post-transplant outcomes, including day 5 or 7 serum creatinine (p = 0.11; p = 0.16), immediate graft function (p = 0.91), creatinine clearance and biopsy-proven rejection at one year (p = 0.14; p = 0.59). LC-MS/MS validation experiments of samples detected FMN in only one perfusate sample, whilst the majority of samples with the highest fluorescence (n = 37/38, 97.4%) remained negative. In the context of clinical kidney HMP, fluorescence spectroscopy unfortunately appears to be not specific and probably unsuitable for FMN. This study shows that FMN does not classify as a clinically relevant predictive biomarker of kidney graft function after transplantation.

First Multicenter Clinical Trial on Machine Perfusion Preservation for Marginal Donor Kidney Transplantation in Japan

BACKGROUND

Machine perfusion has not been widely used because of its low demand in Japan; however, we believe its advantages may increase the number of organ transplants.

METHODS

Here, we report the first clinical trial of machine perfusion for kidney transplantation in Japan. We used the CMP-X08 perfusion device (Chuo-Seiko Co, Ltd, Asahikawa, Hokkaido, Japan) to preserve the donated organs. The flow rate, perfusion pressure, renal resistance, and temperature were monitored during continuous hypothermic perfusion.

RESULTS

From August 2020 to the present, 13 cases of perfusion-preserved kidney transplantation have been performed. Of these, ten and 3 cases were performed using organs donated after brain death (DBD) and cardiac death (DCD), respectively. The average age of the recipients was 55.9 ± 7.3 (45-66) years. The average dialysis period was 14.8 ± 8.4 (0-26) years. The donor's final creatinine level before organ retrieval was 1.58 ± 1.0 (0.46-3.07) mg/dL. The warm ischemic times of the 3 DCD donors were 3, 12, and 18 minutes. The average total ischemic time was 12.0 ± 3.7 (7.17-19.88) hours. The average MP time was 140 (60-240) minutes. A total of 7 cases had delayed graft function. The best creatinine level during hospitalization was 1.17 ± 0.43 (0.71-1.85) mg/dL. There were no primary non-functional cases, and perfusion preservation was safely performed in all cases.

CONCLUSIONS

Therefore, we present this report as the first clinical trial on machine perfusion for kidney transplantation from marginal donors with DBD and DCD in Japan.

Untargeted metabolomics of perfusate and their association with hypothermic machine perfusion and allograft failure

Although hypothermic machine perfusion (HMP) is associated with improved kidney graft viability and function, the underlying biological mechanisms are unknown. Untargeted metabolomic profiling may identify potential metabolites and pathways that can help assess allograft viability and contribute to organ preservation. Therefore, in this multicenter study, we measured all detectable metabolites in perfusate collected at the beginning and end of deceased-donor kidney perfusion and evaluated their associations with graft failure. In our cohort of 190 kidney transplants, 33 (17%) had death-censored graft failure over a median follow-up of 5.0 years (IQR 3.0-6.1 years). We identified 553 known metabolites in perfusate and characterized their experimental and biological consistency through duplicate samples and unsupervised clustering. After perfusion-time adjustment and false discovery correction, six metabolites in post-HMP perfusate were significantly associated with death-censored graft failure, including alpha-ketoglutarate, 3-carboxy-4-methyl-5-propyl-2-furanpropanoate, 1-carboxyethylphenylalanine, and three glycerol-phosphatidylcholines. All six metabolites were associated with an increased risk of graft failure (Hazard Ratio per median absolute deviation range 1.04-1.45). Four of six metabolites also demonstrated significant interaction with donation after cardiac death with notably greater risk in the donation after cardiac death group (Hazard Ratios up to 1.69). Discarded kidneys did not have significantly different levels of any death-censored graft failure-associated metabolites. On interrogation of pathway analysis, production of reactive oxygen species and increased metabolism of fatty acids were upregulated in kidneys that subsequently developed death-censored graft failure. Thus, further understanding the role of these metabolites may inform the HMP process and help improve the objective evaluation of allograft offers, thereby reducing the discard of potentially viable organs.

American Society of Transplant Surgeons recommendations on best practices in donation after circulatory death organ procurement

The American Society of Transplant Surgeons supports efforts to increase the number of organs that are critically needed for patients desperately awaiting transplantation. In the United States, transplantation using organs procured from donation after circulatory death (DCD) donors has continued to increase in number. Despite these increases, substantial variability in the utilization and practices of DCD transplantation still exists. To improve DCD organ utilization, it is important to create a set of best practices for DCD recovery. The following recommendations aim to provide guidance on contemporary issues surrounding DCD organ procurement in the United States. A work group was composed of members of the American Society of Transplant Surgeon Scientific Studies Committee and the Thoracic Organ Transplantation Committee. The following topics were identified by the group either as controversial or lacking standardization: prewithdrawal preparation, definition of donor warm ischemia time, DCD surgical technique, combined thoracic and abdominal procurements, and normothermic regional perfusion. The proposed recommendations were classified on the basis of the grade of available evidence and the strength of the recommendation. This information should be valuable for transplant programs as well as for organ procurement organizations and donor hospitals as they develop robust DCD donor procurement protocols.

External pressure dynamics promote kidney viability and perfusate filtration during ex vivo kidney perfusion

Normothermic machine perfusion (NMP) has not yet been established as a technique for preserving organs for a day. A key contributing factor to the same is that the perfusing solutions cannot circulate continuously and evenly in the organs. Here, we conceived a method of applying intermittent air pressure from outside the organ to assist its circulatory distribution during perfusion. We used a perfusion culture system while applying external pressure to culture rat kidneys and compared the circulatory distribution in the kidneys, changes in tissue morphology due to injury, and perfusate filtration. The intermittent pressurization (IMP) (-) group showed markedly poorer circulation on the upper side compared with that in the lower side, alongside histological damage. On the other hand, the IMP (+) group showed improved circulation in the upper side and had lesser histological damage. Furthermore, the IMP (+) group maintained the ability to filter perfusate for 24 h. In transplantation medicine and regenerative medicine research, this method has the potential to contribute to more efficient organ preservation and more functional tissue regeneration in the future.

Breaking the limits of experimental pancreas transplantation: Working toward the clinical ideal graft

Pancreas transplantation is, at present, the only curative treatment for type-1 diabetes that maintains normoglycemia thus avoiding complications arising from poor glycemic control. Despite its great benefits, the number of pancreas transplants has decreased significantly since its inception in the late 1960s, largely due to demographic changes and the consequent suboptimal quality of donors. The selection criteria for pancreas donors mainly depend on morphological variables such as fatty infiltration, fibrosis, or edema, as well as both functional (amylase and lipase) and clinical variables of the donor. However, the final criterion in the decision-making process is the somewhat subjective assessment of a trained surgeon. That being said, the recent incorporation of graft perfusion machines into clinical practice seems to be changing the work dynamics of the donor organ retrieval team, facilitating decision-making based on objective morphological and functional criteria. Normothermic perfusion using perfusate with supplemental oxygen replicates near physiological parameters thus being a promising strategy for organ preservation. Nevertheless, optimum perfusion parameters are difficult to establish in pancreas transplantation given its complex vascular anatomy combined with an intrinsically low blood flow. The objective of this work is to analyze the results published in the recent literature relating to the considerations of ex-vivo normothermic graft perfusion machines and their usefulness in the field of pancreas transplantation.

Normothermic Machine Perfusion in Renal Transplantation

Purpose of Review

Normothermic machine perfusion (NMP) is a promising new tool in kidney transplantation to improve the outcome of marginal donor kidney transplantation. This review examines the current evidence for NMP in clinical practice and considers how the technology may be used in the future.

Recent Findings and Summary

There is emerging evidence to suggest that NMP has the potential to expand the donor pool of transplantable organs. The safety and feasibility of NMP have been established in a number of clinical studies but more research is needed to optimise the perfusion conditions. NMP shows promise as a viability assessment tool with particular focus on biomarkers and imaging techniques which provide real-time information to facilitate transplantation decision-making. Moreover, the exciting development of new potential therapeutics such as cell and gene-based therapies which are deliverable during NMP may also improve and recondition grafts prior to implantation.

The Effect of Hypothermic Machine Perfusion to Ameliorate Ischemia-Reperfusion Injury in Donor Organs

Hypothermic machine perfusion (HMP) has become the new gold standard in clinical donor kidney preservation and a promising novel strategy in higher risk donor livers in several countries. As shown by meta-analysis for the kidney, HMP decreases the risk of delayed graft function (DGF) and improves graft survival. For the liver, HMP immediately prior to transplantation may reduce the chance of early allograft dysfunction (EAD) and reduce ischemic sequelae in the biliary tract. Ischemia-reperfusion injury (IRI), unavoidable during transplantation, can lead to massive cell death and is one of the main causes for DGF, EAD or longer term impact. Molecular mechanisms that are affected in IRI include levels of hypoxia inducible factor (HIF), induction of cell death, endothelial dysfunction and immune responses. In this review we have summarized and discussed mechanisms on how HMP can ameliorate IRI. Better insight into how HMP influences IRI in kidney and liver transplantation may lead to new therapies and improved transplant outcomes.

Exploring Porcine Precision-Cut Kidney Slices as a Model for Transplant-Related Ischemia-Reperfusion Injury

Marginal donor kidneys are more likely to develop ischemia-reperfusion injury (IRI), resulting in inferior long-term outcomes. Perfusion techniques are used to attenuate IRI and improve graft quality. However, machine perfusion is still in its infancy, and more research is required for optimal conditions and potential repairing therapies. Experimental machine perfusion using porcine kidneys is a great way to investigate transplant-related IRI, but these experiments are costly and time-consuming. Therefore, an intermediate model to study IRI would be of great value. We developed a precision-cut kidney slice (PCKS) model that resembles ischemia-reperfusion and provides opportunities for studying multiple interventions simultaneously. Porcine kidneys were procured from a local slaughterhouse, exposed to 30 min of warm ischemia, and cold preserved. Subsequently, PCKS were prepared and incubated under various conditions. Adenosine triphosphate (ATP) levels and histological tissue integrity were assessed for renal viability and injury. Slicing did not influence tissue viability, and PCKS remained viable up to 72 h incubation with significantly increased ATP levels. Hypothermic and normothermic incubation led to significantly higher ATP levels than baseline. William’s medium E supplemented with Ciprofloxacin (and Amphotericin-B) provided the most beneficial condition for incubation of porcine PCKS. The porcine PCKS model can be used for studying transplant IRI.

Trends and Outcomes of Hypothermic Machine Perfusion Preservation of Kidney Allografts in Simultaneous Liver and Kidney Transplantation in the United States

Optimal kidney graft outcomes after simultaneous liver-kidney (SLK) transplant may be threatened by the increased cold ischemia time and hemodynamic perturbations of dual organ transplantation. Hypothermic machine perfusion (MP) of kidney allografts may mitigate these effects. We analyzed U.S. trends and renal outcomes of hypothermic non-oxygenated MP vs. static cold storage (CS) of kidney grafts from 6,689 SLK transplants performed between 2005 and 2020 using the United Network for Organ Sharing database. Outcomes included delayed graft function (DGF), primary non-function (PNF), and kidney graft survival (GS). Overall, 17.2% of kidney allografts were placed on MP. Kidney cold ischemia time was longer in the MP group (median 12.8 vs. 10.0 h; p < 0.001). Nationally, MP utilization in SLK increased from <3% in 2005 to >25% by 2019. Center preference was the primary determinant of whether a graft underwent MP vs. CS (intraclass correlation coefficient 65.0%). MP reduced DGF (adjusted OR 0.74; p = 0.008), but not PNF (p = 0.637). Improved GS with MP was only observed with Kidney Donor Profile Index <20% (HR 0.71; p = 0.030). Kidney MP has increased significantly in SLK in the U.S. in a heterogeneous manner and with variable short-term benefits. Additional studies are needed to determine the ideal utilization for MP in SLK.

(Cast2021) Oxygenated Hypothermic Machine Perfusion of Kidney Transplantation from Donors After Cardiac Death Due to Long-Term Low Blood Pressure and Hypoxia: The First Case Report of a Clinical Trial Using a New Japanese Perfusion System

BACKGROUND

Machine perfusion of marginal kidney grafts obtained from donors after cardiac death (DCD) has become a standard therapy worldwide. However, the use of grafts from DCD due to long-term low blood pressure is associated with a high incidence of primary graft nonfunction. Furthermore, the importance of oxygenation in machine perfusion remains unclear. We report the first case of a clinical trial of a kidney transplant obtained from a DCD using a Japanese oxygenated hypothermic perfusion system (CMX-08W, Chuo Seiko Co Ltd, Asahikawa, Japan).

PATIENTS AND METHODS

The donor was a 61-year-old man with amyotrophic lateral sclerosis. His SpO₂ decreased to 80% to 90%, his blood pressure remained consistently low for 4 hours and 30 minutes, and he suffered a cardiac arrest. Subsequently, we carried him to the operating room. The warm ischemic time was 12 minutes, and the cold ischemic time was 418 minutes. The recipient was a 58-year-old man who had been undergoing hemodialysis for 26 years. He was diagnosed with nephrosclerosis and multiple renal cysts. Oxygenated hypothermic machine perfusion was used on the kidney transplant obtained from the DCD.

RESULTS

The recipient gradually recovered and was withdrawn from hemodialysis therapy 14 days post transplantation. His renal function improved, and he was discharged on postoperative day 36. Currently, his renal function remains good (phosphocreatine, 1.7).

CONCLUSIONS

Oxygenated machine perfusion is used to preserve organs and determine if an organ is suitable for transplantation. This may provide the possibility of perfusion preservation and expand the criteria for cardiac arrest-associated renal transplantation.

Factors Associated With the Use of Hypothermic Machine Perfusion in Kidney Transplant Recipients: A Multicenter Retrospective Cohort Study

Background:

Delayed graft function (DGF) is associated with an increased risk of graft loss. The use of cold hypothermic machine perfusion (HMP) has been shown to reduce the incidence of DGF in kidney transplant recipients (KTRs), especially when extended-criteria donors (ECDs) are used. HMP can also improve graft survival. However, there is a paucity of data on the determinants of HMP use in clinical practice.

Objective:

We aimed to determine the factors associated with the use of HMP in a cohort of donors and KTRs.

Design:

Multicenter retrospective cohort study.

Setting:

5 transplant centers in Quebec.

Patients:

159 neurologically deceased donors (NDD) and 281 KTR.

Measurements:

Use of HMP.

Methods:

We collected data on consecutive NDD admitted to a dedicated donor unit in a single university-affiliated center and their KTRs between June 2013 and December 2018 in 5 adult transplant centers across the province of Quebec, Canada. All organs were recovered in a single hospital center where a HMP device was available for every organ recovered and the decision to use HMP was left at the discretion of the procurement surgeon. Generalized estimating equations were used to predict the use of HMP.

Results:

The cohort included 159 NDDs and their 281 KTRs. Thirty-three percent of donors were ECDs, and 59% of KTRs received organs placed on HMP. The median cold ischemia time (CIT) was 12.5 (IQR 7.9-16.3) hours. In univariate analysis, none of the donors’ characteristics were associated with the use of HMP. ECD represented 33% of KTR on HMP vs 35% of those not placed on HMP (P = .77). In univariate analysis, the use of HMP was associated with KTR race (non-Caucasian), longer CIT, use of basiliximab/alemtuzumab, year of transplant, and transplant center. The use of HMP varied largely across transplant centers, ranging from 15% to 82%. In multivariate analysis, use of HMP was associated with longer CIT (odds ratio [OR] 1.15, 95% confidence interval [CI] = 1.07-1.25), transplant center as well as transplantations performed after 2013.

Limitations:

One dedicated donor unit including NDD only, absence of specific data on surgeons’ experience and personal or logistic reasons for using or not HMP.

Conclusions:

We found that use of HMP remains low and varies largely across transplant centers. The use of HMP was strongly associated with the transplant center where the surgeons practiced, suggesting that surgeon preference/training plays an important role in determining the use of HMP. Availability of HMP at the time of organ procurement might also be limited by logistic issues such as difficulty in returning the device. Further studies aimed at determining the reasons underlying the barriers precluding the use of HMP could help increasing its use and improve transplant outcomes.

Disparate Formulations for Machine Perfusion: A Survey of Organ Procurement Organizations' Medication Additives and Outcome Analyses

OBJECTIVES

Machine perfusionfor kidney preservation is a common practice. There is no consensus on the best formula for perfusion solutions. We aimed to discern the additives that organ procurement organizations in the United States include in their perfusate and the impact of these additives on transplant outcomes.

MATERIALS AND METHODS

A telephone survey of all 58 organ procurement organizations in the United States regarding additives to their perfusion solutions was conducted. The survey data were merged with transplant recipient outcome data from the United Network for Organ Sharing database.The final analysis included perfused kidneys between January 2014 and March 2019. Logistic regressions were performed to investigate whether a particular perfusion formula was associated with delayed graft function, primary nonfunction, or early graft failure.

RESULTS

Additives correlated with decreased rates of graft failure were mannitol in all kidneys and kidneys of lower quality (P < .01) and penicillin/ampicillin in all kidneys (P < .05). Additives associated with increased graft failure regardless of type included verapamil in all kidneys (P < .05) and kidneys of lower quality (P < .01) and arginine with glutathione in all kidneys and low-quality kidneys alone (P < .01).

CONCLUSIONS

Further outcomes research and standardized guidelines for additives in machine perfusion of kidneys across all organ procurement organizations are needed.

Advances in Kidney Preservation Techniques and Their Application in Clinical Practice

The use of cold preservation solutions to rapidly flush and cool the kidney followed by static cold storage in ice has been the standard kidney preservation technique for the last 50 y. Nonetheless, changing donor demographics that include organs from extended criteria donors and donation after circulatory death donors have led to the adoption of more diverse techniques of preservation. Comparison of hypothermic machine perfusion and static cold storage techniques for deceased donor kidneys has long been debated and is still contested by some. The recent modification of hypothermic machine perfusion techniques with the addition of oxygen or perfusion at subnormothermic or near-normothermic temperatures are promising strategies that are emerging in clinical practice. In addition, the use of normothermic regional perfusion to resuscitate abdominal organs of donation after circulatory death donors in situ before cold flushing is also increasingly being utilized. This review provides a synopsis of the different types of preservation techniques including their mechanistic effects and the outcome of their application in clinical practice for different types of donor kidney.

Vitrification and Nanowarming of Kidneys

Vitrification can dramatically increase the storage of viable biomaterials in the cryogenic state for years. Unfortunately, vitrified systems ≥3 mL like large tissues and organs, cannot currently be rewarmed sufficiently rapidly or uniformly by convective approaches to avoid ice crystallization or cracking failures. A new volumetric rewarming technology entitled "nanowarming" addresses this problem by using radiofrequency excited iron oxide nanoparticles to rewarm vitrified systems rapidly and uniformly. Here, for the first time, successful recovery of a rat kidney from the vitrified state using nanowarming, is shown. First, kidneys are perfused via the renal artery with a cryoprotective cocktail (CPA) and silica-coated iron oxide nanoparticles (sIONPs). After cooling at -40 °C min-1 in a controlled rate freezer, microcomputed tomography (µCT) imaging is used to verify the distribution of the sIONPs and the vitrified state of the kidneys. By applying a radiofrequency field to excite the distributed sIONPs, the vitrified kidneys are nanowarmed at a mean rate of 63.7 °C min-1 . Experiments and modeling show the avoidance of both ice crystallization and cracking during these processes. Histology and confocal imaging show that nanowarmed kidneys are dramatically better than convective rewarming controls. This work suggests that kidney nanowarming holds tremendous promise for transplantation.

Effect of delayed graft function on longer-term outcomes after kidney transplantation from donation after circulatory death donors in the United Kingdom: A national cohort study

Kidneys from donation after circulatory death (DCD) donors are utilized variably worldwide, in part due to high rates of delayed graft function (DGF) and putative associations with adverse longer-term outcomes. We aimed to determine whether the presence of DGF and its duration were associated with poor longer-term outcomes after kidney transplantation from DCD donors. Using the UK transplant registry, we identified 4714 kidney-only transplants from controlled DCD donors to adult recipients between 2006 and 2016; 2832 recipients (60·1%) had immediate graft function and 1882 (39·9%) had DGF. Of the 1847 recipients with DGF duration recorded, 926 (50·1%) had DGF < 7 days, 576 (31·2%) had DGF 7-14 days, and 345 (18·7%) had DGF >14 days. After risk adjustment, the presence of DGF was not associated with inferior long-term graft or patient survivals. However, DGF duration of >14 days was associated with an increased risk of death-censored graft failure (hazard ratio 1·7, p = ·001) and recipient death (hazard ratio 1·8, p < ·001) compared to grafts with immediate function. This study suggests that shorter periods of DGF have no adverse influence on graft or patient survival after DCD donor kidney transplantation and that DGF >14 days is a novel early biomarker for significantly worse longer-term outcomes.

Efficacy and Safety of Machine Perfusion for Brain Death Marginal Donor Kidney Transplantation: A Report of 2 Cases

BACKGROUND

After the revised organ transplant law came into effect in Japan, donations of organs under brain death have been increasing; however, because of the expansion of donor indications, donations from expanded criteria donors and cardiac arrest donors (donation after cardiac death) have also increased. In kidney transplantation, ischemia-reperfusion injury results in a high rate of delayed graft function, which adversely affects patients' long-term prognoses. Hypothermic machine perfusion preservation results in superior postoperative function and survival rates compared with cold storage preservation. We used an organ preservation device for kidneys and performed a graft viability evaluation before to kidney transplantation.

METHODS

We used the CMP-X08 perfusion device (Chuo-Seiko Co, Ltd, Asahikawa, Hokkaido, Japan) and Belzer MPS solution to preserve the donated organ. The perfusion pressure and temperature were monitored during cold storage with continuous perfusion. Standard renal transplantation protocols were followed. A renal biopsy was performed 1 hour after transplantation and the renal function was evaluated. This study followed the principles of the Declaration of Helsinki.

RESULTS

The first presented case is of a 63-year-old woman who received a kidney from a middle-aged man with brain death due to hypoxic encephalopathy. The creatinine at the time of admission was 0.9 mg/dL and at the time of excision was 2.86 mg/dL. The total perfusion time was 120 minutes. The total ischemia time was 7 hours and 15 minutes. The recipient urinated 115 minutes postoperatively, and no dialysis was required. The second presented case is of a 47-year-old man with a 15-year history of dialysis who received a kidney from a middle-aged woman with brain death due to subarachnoid hemorrhage. The creatinine at the time of admission was 0.8 mg/dL and at the time of excision was 0.77 mg/dL. The total perfusion time was 240 minutes. The total ischemia time was 13 hours and 14 minutes. The recipient urinated 38 minutes postoperatively, and no dialysis was required.

CONCLUSIONS

Mechanical perfusion storage performed for 2 to 4 hours resulted in a viable organ that was successfully transplanted in both cases.

Subnormothermic Perfusion with H2S Donor AP39 Improves DCD Porcine Renal Graft Outcomes in an Ex Vivo Model of Kidney Preservation and Reperfusion

Cold preservation is the standard of care for renal grafts. However, research on alternatives like perfusion at higher temperatures and supplementing preservation solutions with hydrogen sulfide (H₂S) has gained momentum. In this study, we investigated whether adding H₂S donor AP39 to porcine blood during subnormothermic perfusion at 21 °C improves renal graft outcomes. Porcine kidneys were nephrectomized after 30 min of clamping the renal pedicles and treated to 4 h of static cold storage (SCS) on ice or ex vivo subnormothermic perfusion at 21 °C with autologous blood alone (SNT) or with AP39 (SNTAP). All kidneys were reperfused ex vivo with autologous blood at 37 °C for 4 h. Urine output, histopathology and RNAseq were used to evaluate the renal graft function, injury and gene expression profiles, respectively. The SNTAP group exhibited significantly higher urine output than other groups during preservation and reperfusion, along with significantly lower apoptotic injury compared to the SCS group. The SNTAP group also exhibited differential pro-survival gene expression patterns compared to the SCS (downregulation of pro-apoptotic genes) and SNT (downregulation of hypoxia response genes) groups. Subnormothermic perfusion at 21 °C with H₂S-supplemented blood improves renal graft outcomes. Further research is needed to facilitate the clinical translation of this approach.

[Machine perfusion for conditioning liver and kidneys before transplantation]

Machine perfusion will become established as the standard of care for solid organ transplantation in the near future. Ongoing studies are investigating the appropriate perfusion algorithms for each specific organ. Although it is neither proven which perfusion principle nor type of device is superior, it has already been sufficiently shown that the increasing number of marginal organs that are currently transplanted in Germany would benefit from machine perfusion for conditioning before transplantation. The addition of hypothermic and normothermic perfusion sequences opens up the possibility of conditioning of previously damaged organs as well as viability testing. Overall, machine perfusion increases the safety for the recipient and can counteract the increasingly more difficult scenario of working hour restrictions because solid organ transplantations in the future will be plannable and carried out during the day.

A Retrospective Propensity Score Matched Analysis Reveals Superiority of Hypothermic Machine Perfusion over Static Cold Storage in Deceased Donor Kidney Transplantation

Hypothermic machine perfusion (HMP) has been introduced as an alternative to static cold storage (SCS) in kidney transplantation, but its true benefit in the clinical routine remains incompletely understood. The aim of this study was to assess the effect of HMP vs. SCS in kidney transplantation. All kidney transplants performed between 08/2015 and 12/2019 (n = 347) were propensity score (PS) matched for cold ischemia time (CIT), extended criteria donor (ECD), gender mismatch, cytomegalovirus (CMV) mismatch, re-transplantation and Eurotransplant (ET) senior program. A total of 103 HMP and 103 SCS instances fitted the matching criteria. Prior to PS matching, the CIT was longer in the HMP group (17.5 h vs. 13.3 h; p < 0.001), while the delayed graft function (DGF) rates were 29.8% and 32.3% in HMP and SCS, respectively. In the PS matched groups, the DGF rate was 64.1% in SCS vs. 31.1% following HMP: equivalent to a 51.5% reduction of the DGF rate (OR 0.485, 95% CI 0.318–0.740). DGF was associated with decreased 1- and 3-year graft survival (100% and 96.3% vs. 90.8% and 86.7%, p = 0.001 and p = 0.008) or a 4.1-fold increased risk of graft failure (HR = 4.108; 95% CI: 1.336–12.631; p = 0.014). HMP significantly reduces DGF in kidney transplantation. DGF remains a strong predictor of graft survival.