Normothermic Machine Perfusion Research Articles

From Patients to Providers: Assessing Impact of Normothermic Machine Perfusion on Liver Transplant Practices in the US.

Normothermic machine perfusion (NMP) of livers allows for the expansion of the donor pool and minimization of posttransplant complications. Results to date have focused on both donor and recipient outcomes, but there remains potential for NMP to also impact transplant providers. Using United Network for Organ Sharing Standard Transplant Analysis file data, adult deceased donors who underwent transplantation between January 1, 2016, and December 31, 2022, were identified. Transplanted livers were divided by preservation methods (static cold storage [SCS] and NMP) and case time (day-reperfusion 8 am to 6 pm ). Patient factors, transplant characteristics, and short-term outcomes were analyzed between Mahalanobis-metric-matched groups. NMP livers represented 742 (1.4%) of 52,132 transplants. NMP donors were more marginal with higher Donor Risk Index scores (1.78 ± 0.50 NMP vs 1.49 ± 0.38 SCS, p < 0.001) and donation after cardiac death frequency (36.9% vs 8.4%, p < 0.001). NMP recipients more often had model for end-stage liver disease (MELD) exception status (29.9% vs 23.4%, p < 0.001), lower laboratory MELD scores (20.7 ± 9.7 vs 24.3 ± 10.9, p < 0.001), and had been waitlisted longer (111.5 [21.0 to 307.0] vs 60.0 [9.0 to 245.0] days, p < 0.001). One-year graft survival (90.2% vs 91.6%, p = 0.505) was similar between groups, whereas length of stay was lower for NMP recipients (8.0 [6.0 to 14.0] vs 10.0 [6.0 to 16.0], p = 0.017) after adjusting for confounders. Notably, peak case volume occurred at 11 am with NMP livers (vs 9 pm with SCS). Overall, a higher proportion of transplants was performed during daytime hours with NMP (51.5% vs 43.0%, p < 0.001). NMP results in increased use of marginal allografts, which facilitated transplantation in lower laboratory MELD recipients who have been waitlisted longer and often have exception points. Importantly, NMP also appeared to shift peak caseloads from nighttime to daytime, which may have significant effects on the quality of life for the entire liver transplant team.

Enhancing the usability of older DCD donors through strategic approaches in liver transplantation in the United States.

The use of older donors after circulatory death (DCD) for liver transplantation (LT) has increased over the past decade. This study examined whether outcomes of LT using older DCD (≥50y) have improved with advancements in surgical/perioperative care and normothermic machine perfusion (NMP) technology. A total of 7602 DCD LT cases from the United Network for Organ Sharing database (2003-2022) were reviewed. The impact of older DCD donors on graft survival was assessed using the Kaplan-Meier and HR analyses. In all, 1447 LT cases (19.0%) involved older DCD donors. Although there was a decrease in their use from 2003 to 2014, a resurgence was noted after 2015 and reached 21.9% of all LTs in the last 4 years (2019-2022). Initially, 90-day and 1-year graft survivals for older DCDs were worse than younger DCDs, but this difference decreased over time and there was no statistical difference after 2015. Similarly, HRs for graft loss in older DCD have recently become insignificant. In older DCD LT, NMP usage has increased recently, especially in cases with extended donor-recipient distances, while the median time from asystole to aortic cross-clamp has decreased. Multivariable Cox regression analyses revealed that in the early phase, asystole to cross-clamp time had the highest HR for graft loss in older DCD LT without NMP, while in the later phases, the cold ischemic time (>5.5h) was a significant predictor. LT outcomes using older DCD donors have become comparable to those from young DCD donors, with recent HRs for graft loss becoming insignificant. The strategic approach in the recent period could mitigate risks, including managing cold ischemic time (≤5.5h), reducing asystole to cross-clamp time, and adopting NMP for longer distances. Optimal use of older DCD donors may alleviate the donor shortage.

Application of Nanotechnology in Organ Transplantation

Organ transplantation can serve as a blessing for end-stage organ patients, and issues such as organ shortage and transplantation risks also make research on organ transplantation very important. Nanotechnology involves the development of materials called nanoparticles, which are defined as having a one-dimensional range of at least 1 to 100 nm. This paper introduces the application of nanotechnology in overcoming the drawbacks of traditional medicine, and its nanoscale size has also contributed to organ transplantation. The combination of Magnetic resonance imaging (MRI) and Magnetic hyperthermia (MHT), nanoparticles can better capture transplant medical images, and nanotechnology plays an important role in monitoring treatment responses and designing organ transplantation methods. CRISPR/CAS9 system and Entrancer™ can reduce the role in rejection reactions. Normothermic Machine Perfusion (NMP), protein corona, and curcumin can reduce their effects on ischemia-reperfusion injury. The development of nanomedicine can provide a platform for significant progress in transplant vitality. In future research, nanoparticles can also be applied in 3D bioprinting and artificial intelligence (AI) to better assist in transplant therapy.

Hypothermic Oxygenated Perfusion Improves Vascular and Contractile Function by Preserving Endothelial Nitric Oxide Production in Cardiac Grafts Obtained With Donation After Circulatory Death.

Cardiac donation after circulatory death is a promising option to increase graft availability. Graft preservation with 30 minutes of hypothermic oxygenated perfusion (HOPE) before normothermic machine perfusion may improve cardiac recovery as compared with cold static storage, the current clinical standard. We investigated the role of preserved nitric oxide synthase activity during HOPE on its beneficial effects. Using a rat model of donation after circulatory death, hearts underwent insitu ischemia (21 minutes), were explanted for a cold storage period (30 minutes), and then reperfused under normothermic conditions (60 minutes) with left ventricular loading. Three cold storage conditions were compared: cold static storage, HOPE, and HOPE with Nω-nitro-L-arginine methyl ester (nitric oxide synthase inhibitor). To evaluate potential confounding effects of high coronary flow during early reperfusion in HOPE hearts, bradykinin was administered to normalize coronary flow to HOPE levels in 2 additional groups (cold static storage and HOPE with Nω-nitro-L-arginine methyl ester). Cardiac recovery was significantly improved in HOPE versus cold static storage hearts, as determined by cardiac output, left ventricular work, contraction and relaxation rates, and coronary flow (P<0.05). Furthermore, HOPE attenuated postreperfusion calcium overload. Strikingly, the addition of Nω-nitro-L-arginine methyl ester during HOPE largely abolished its beneficial effects, even when early reperfusion coronary flow was normalized to HOPE levels. HOPE provides superior preservation of ventricular and vascular function compared with the current clinical standard. Importantly, HOPE's beneficial effects require preservation of nitric oxide synthase activity during the cold storage. Therefore, the application of HOPE before normothermic machine perfusion is a promising approach to optimize graft recovery in donation after circulatory death cardiac grafts.

Activation of farnesoid X receptor enhances the efficacy of normothermic machine perfusion in ameliorating liver ischemia-reperfusion injury

The shortage of transplant organs remains a severe global issue. Normothermic machine perfusion (NMP) has the potential to increase organ availability, yet its efficacy is hampered by the inflammatory response during machine perfusion. Mouse liver ischemia-reperfusion injury (IRI) models, discarded human liver models, and porcine marginal liver transplantation models were utilized to investigate whether farnesoid X receptor (FXR) activation could mitigate inflammation-induced liver damage. FXR expression levels before and after reperfusion were measured. Gene editing and coimmunoprecipitation techniques were employed to explore the regulatory mechanism of FXR in inflammation inhibition. The expression of FXR correlates with the extent of liver damage after reperfusion. Activation of FXR significantly suppressed the inflammatory response triggered by IRI, diminished the release of proinflammatory cytokines, and improved liver function recovery during NMP, assisting discarded human livers to reach transplant standards. Mechanistically, FXR disrupts the interaction between p65 and p300, thus inhibiting modulating the nuclear factor kappa-B signaling pathway, a key instigator of inflammation. Our research across multiple species confirms that activating FXR can optimize NMP by attenuating IRI-related liver damage, thereby improving the utilization of marginal livers for transplantation.

Development of a Large Animal Model of Ischemia-free Liver Transplantation in Pigs.

In organ transplantation, ischemia, and reperfusion injury (IRI) is considered as an inevitable event and the major contributor to graft failure. Ischemia-free liver transplantation (IFLT) is a novel transplant procedure that can prevent IRI and provide better transplant outcomes. However, a large animal model of IFLT has not been reported. Therefore, we develop a new, reproducible, and stable model of IFLT in pigs for investigating mechanisms of IFLT in IRI. Ten pigs were subjected to IFLT or conventional liver transplantation (CLT). Donor livers in IFLT underwent 6-h continuous normothermic machine perfusion (NMP) throughout graft procurement, preservation, and implantation, whereas livers in CLT were subjected to 6-h cold storage before implantation. The early reperfusion injury was compared between the 2 groups. Continuous bile production, low lactate, and liver enzyme levels were observed during NMP in IFLT. All animals survived after liver transplantation. The posttransplant graft function was improved with IFLT when compared with CLT. Minimal histologic changes, fewer apoptotic hepatocytes, less sinusoidal endothelial cell injury, and proinflammatory cytokine (interleukin [IL]-1β, IL-6, and tumor necrosis factor-α) release after graft revascularization were documented in the IFLT group versus the CLT group. We report that the concept of IFLT is achievable in pigs. This innovation provides a potential strategy to investigate the mechanisms of IRI and provide better transplant outcomes for clinical practice.

National Trends in Utilization of Normothermic Machine Perfusion in DCD Liver Transplantation.

In liver transplantation, advances in ex situ normothermic machine perfusion (NMP) have improved outcomes compared with traditional static cold storage (SCS) in donation after circulatory death (DCD) organs. We aimed to characterize trends in the utilization of NMP versus SCS in DCD liver transplantation in the United States. This retrospective cohort study used data from the United Network for Organ Sharing database to identify recipient-donor adult liver transplant pairs from DCD donors from January 2016 to June 2022. Utilization of NMP and changes in donor risk index (DRI) and components between NMP and SCS were assessed across transplant year eras (2016-2018, 2019-2020, and 2021-2022). Statistical comparisons were made using the Kruskal-Wallis test or the chi-square test. A total of 3937 SCS and 127 NMP DCD donor transplants were included. Utilization of NMP ranged from ~0.4% to 3.5% from 2016 to 2021 and rose significantly to 11.2% in early 2022. Across transplant eras, median DRI increased significantly for SCS and NMP, but the magnitude of the increase was larger for NMP. With NMP DCDs, there were significant increases in median donor age, national share proportion, and "cold ischemic time" over time. Finally, there was a shift toward including higher DRI donors and higher model for end-stage liver disease score transplant recipients with NMP in later transplant eras. In recent years, NMP utilization has increased and expanded to donors with higher DRI and recipients with higher model for end-stage liver disease score at transplant, suggesting increasing familiarity and risk tolerance with NMP technology. As NMP remains a relatively new technique, ongoing study of patient outcomes, organ allocation practices, and utilization patterns is critical.

An Unexpected Partnership: Alexis Carrel, Charles Lindbergh, and Normothermic Machine Perfusion.

Organ transplantation is a triumph of modern medicine which represents a culmination of science and imagination, saving thousands of lives a year. However, transplantation is severely limited by suitable donor allografts. To expand the donor pool and make transplantation achievable for all, normothermic machine perfusion (NMP) is being employed more frequently. Normothermic machine perfusion involves the utilization of a device to approximate the physiology of the human body, preserve organs outside of the donor, and provide a dynamic assessment platform to determine organ suitability for transplantation. As NMP technology advances, it will soon be possible to genetically modify and actively repair these organs. Although its application to the field of transplantation is relatively new, the concept, foundation, and development of NMP can be traced back to the pioneering work of the surgeon-scientist, Alexis Carrel and the famous aviator, Charles Lindbergh in the 1930s. Their collaboration resulted in the Carrel-Lindbergh Perfusion device, an early perfusion device that was able to keep organs alive ex vivo for weeks and is most appropriately viewed as a precursor to modern machine perfusion technologies. As NMP technology becomes more advanced and refined, it is important to acknowledge the historical context in which these technologies emerged.

Ex vivo kidney machine perfusion: meta-analysis of randomized clinical trials.

Machine perfusion is an organ preservation strategy used to improve function over simple storage in a cold environment. This article presents an updated systematic review and meta-analysis of machine perfusion in deceased donor kidneys. RCTs from November 2018 to July 2023 comparing machine perfusion versus static cold storage in kidney transplantation were evaluated for systematic review. The primary outcome in meta-analysis was delayed graft function. A total 19 studies were included, and 16 comparing hypothermic machine perfusion with static cold storage were analysed. The risk of delayed graft function was lower with hypothermic machine perfusion (risk ratio (RR) 0.77, 95% c.i. 0.69 to 0.86), even in kidneys after circulatory death (RR 0.78, 0.68 to 0.90) or brain death (RR 0.73, 0.63 to 0.84). Full hypothermic machine perfusion decreased the risk of delayed graft function (RR 0.69, 0.60 to 0.79), whereas partial hypothermic machine perfusion did not (RR 0.92, 0.69 to 1.22). Normothermic machine perfusion or short-term oxygenated hypothermic machine perfusion preservation after static cold storage was equivalent to static cold storage in terms of delayed graft function and 1-year graft survival. Hypothermic machine perfusion reduces delayed graft function risks and normothermic approaches show promise.

Impact of Back-to-Base Normothermic Machine Perfusion on Complications and Costs: A Multicenter, Real-World Risk-Matched Analysis.

Assess cost and complication outcomes after liver transplantation (LT) using normothermic machine perfusion (NMP). End-ischemic NMP is often used to aid logistics, yet its impact on outcomes after LT remains unclear, as does its true impact on costs associated with transplantation. Deceased donor liver recipients at 2 centers (January 1, 2019, to June 30, 2023) were included. Retransplants, splits, and combined grafts were excluded. End-ischemic NMP (OrganOx-Metra) was implemented in October 2022 for extended-criteria donation after brain death (DBDs), all donations after circulatory deaths (DCDs), and logistics. NMP cases were matched 1:2 with static cold storage controls (SCS) using the Balance-of-Risk [donation after brain death (DBD)-grafts] and UK-DCD Score (DCD-grafts). Overall, 803 transplantations were included, 174 (21.7%) receiving NMP. Matching was achieved between 118 NMP-DBDs with 236 SCS; and 37 NMP-DCD with 74 corresponding SCS. For both graft types, median inpatient comprehensive complications index values were comparable between groups. DCD-NMP grafts experienced reduced cumulative 90-day comprehensive complications index (27.6 vs 41.9, P =0.028). NMP also reduced the need for early relaparotomy and renal replacement therapy, with subsequently less frequent major complications (Clavien-Dindo ≥IVa). This effect was more pronounced in DCD transplants. NMP had no protective effect on early biliary complications. Organ acquisition/preservation costs were higher with NMP, yet NMP-treated grafts had lower 90-day pretransplant costs in the context of shorter waiting list times. Overall costs were comparable for both cohorts. This is the first risk-adjusted outcome and cost analysis comparing NMP and SCS. In addition to logistical benefits, NMP was associated with a reduction in relaparotomy and bleeding in DBD grafts, and overall complications and post-LT renal replacement for DCDs. While organ acquisition/preservation was more costly with NMP, overall 90-day health care costs-per-transplantation were comparable.

Magnetic resonance imaging as a noninvasive adjunct to conventional assessment of functional differences between kidneys in vivo and during ex vivo normothermic machine perfusion

Normothermic machine perfusion (NMP) is increasingly considered for pretransplant kidney quality assessment. However, fundamental questions about differences between in vivo and ex vivo renal function, as well as the impact of ischemic injury on ex vivo physiology, remain unanswered. This study utilized magnetic resonance imaging (MRI), alongside conventional parameters to explore differences between in vivo and ex vivo renal function and the impact of warm ischemia on a kidney’s behavior ex vivo. Renal MRI scans and samples were obtained from living pigs (n = 30) in vivo. Next, kidney pairs were procured and exposed to minimal, or 75 minutes of warm ischemia, followed by 6 hours of hypothermic machine perfusion. Both kidneys simultaneously underwent 6-hour ex vivo perfusion in MRI-compatible NMP circuits to obtain multiparametric MRI data. Ischemically injured ex vivo kidneys showed a significantly altered regional blood flow distribution compared to in vivo and minimally damaged organs. Both ex vivo groups showed diffusion restriction relative to in vivo. Our findings underscore the differences between in vivo and ex vivo MRI-based renal characteristics. Therefore, when assessing organ viability during NMP, it should be considered to incorporate parameters beyond the conventional functional markers that are common in vivo.

(308) - Assessment of Extended Criteria Donor Hearts with Resonance Raman Spectroscopy During Normothermic Machine Perfusion

(308) - Assessment of Extended Criteria Donor Hearts with Resonance Raman Spectroscopy During Normothermic Machine Perfusion

Tissue-resident Lymphocytes Are Released During Hypothermic and Normothermic Machine Perfusion of Human Donor Kidneys.

Machine perfusion is the preferred preservation method for deceased donor kidneys. Perfusate fluid, which contains a complex mixture of components, offers potential insight into the organ's viability and function. This study explored immune cell release, particularly tissue-resident lymphocytes (TRLs), during donor kidney machine perfusion and its correlation with injury markers. Perfusate samples from hypothermic machine perfusion (HMP; n = 26) and normothermic machine perfusion (NMP; n = 16) of human donor kidneys were analyzed for TRLs using flow cytometry. Residency was defined by expressions of CD69, CD103, and CD49as. TRL release was quantified exclusively in NMP. Additionally, levels of cell-free DNA, neutrophil gelatinase-associated lipocalin, and soluble E-cadherin (sE-cadherin) were measured in NMP supernatants with quantitative polymerase chain reaction and enzyme-linked immunosorbent assay. Both HMP and NMP samples contained a heterogeneous population of TRLs, including CD4 + tissue-resident memory T cells, CD8 + tissue-resident memory T cells, tissue-resident natural killer cells, tissue-resident natural killer T cells, and helper-like innate lymphoid cells. Median TRL proportions among total CD45 + lymphocytes were 0.89% (NMP) and 0.84% (HMP). TRL quantities in NMP did not correlate with donor characteristics, perfusion parameters, posttransplant outcomes, or cell-free DNA and neutrophil gelatinase-associated lipocalin concentrations. However, CD103 + TRL release positively correlated with the release of sE-cadherin, the ligand for the CD103 integrin. Human donor kidneys release TRLs during both HMP and NMP. The release of CD103 + TRLs was associated with the loss of their ligand sE-cadherin but not with general transplant injury biomarkers.

Anti-apoptotic treatment of warm ischemic male rat livers in machine perfusion improves symptoms of ischemia-reperfusion injury

BackgroundLiver donation after cardiac death (DCD) makes up a small percentage of the organs used in transplantation and poses a higher risk of graft loss compared to donation after brain death (DBD); this is a result of ischemia reperfusion for which the exact injury mechanisms are currently not fully understood. However, reperfusion injury has been shown to lead to necrosis as well as apoptosis through oxidative stress and mitochondrial dysfunction. In this work, we propose that use of the pro-survival, anti-apoptotic CEPT cocktail in post-ischemia normothermic machine perfusion (NMP) may improve recovery in rat livers subjected to extended durations of warm ischemia. Materials and MethodsLivers procured from male Lewis rats were subjected to 90 min of warm ischemia, followed by 6 h of NMP where they were treated either with the survival-enhancing anti-apoptotic cocktail (CEPT), the vehicle (DMSO) or the base media with no additives. ResultsThe CEPT-treated group exhibited lower expression of hepatic injury biomarkers, and improvement in a range of hepatocellular symptoms associated with the hepatic parenchyma, biliary epithelium and the sinusoidal endothelium, including recovery of bile secretion and lowered vascular resistance. ConclusionsThis study's findings suggest apoptosis plays a more significant role in ischemia-reperfusion injury than previously understood, and provide useful insight for further investigation of the specific underlying mechanisms and development of novel treatment methods.

The establishment of diseased human whole organ model by normothermic machine perfusion technique: Principle of concept.

The global incidence of liver diseases is rising, yet there remains a dearth of precise research models to mimic these diseases. The use of normothermic machine perfusion (NMP) to study diseased livers recovered from liver transplantation (LT) recipients presents a promising avenue. Accordingly, we have developed a machine perfusion system tailored specifically for the human whole diseased livers and present our experience from the NMP of diseased livers. Six diseased livers recovered from LT recipients with different diagnoses were collected. The diseased livers were connected to the machine perfusion system that circulated tailored perfusate, providing oxygen and nutrients. The pressure and flow of the system were recorded, and blood gas analysis and laboratory tests of perfusate and bile were examined to analyze the function of the diseased livers. Liver tissues before and after NMP were collected for histological analysis. Experiments showed that the system maintained the diseased livers in a physiological state, ensuring stable hemodynamics and a suitable partial pressure of oxygen and carbon dioxide. The results of blood gas analysis and laboratory tests demonstrated a restoration and sustenance of metabolism with minimal damage. Notably, a majority of the diseased livers exhibited bile production continuously, signifying their vivid functional integrity. The pathological characteristics remained stable before and after NMP. We successfully established the machine perfusion system tailored specifically for diseased human whole livers. Through the application of this system, we have developed a novel invitro model that faithfully recapitulates the main features of human liver disease. This model holds immense promise as an advanced disease modeling platform, offering profound insights into liver diseases and potential implications for research and therapeutic development.

The association between hemoglobin levels and renal function parameters during normothermic machine perfusion: A retrospective cohort study using porcine kidneys.

Ex vivo normothermic machine perfusion (NMP) is a promising tool for assessing an isolated kidney prior to transplantation. However, there is no consensus on the perfusate's optimal oxygen-carrying capacity to support renal function. To investigate the association of hemoglobin levels with renal function parameters, a retrospective analysis of isolated, normothermically, perfused porcine kidneys was performed. Between 2015 and 2021, a total of 228 kidneys underwent 4 h of NMP with perfusates that varied in hemoglobin levels. A generalized linear model was used to determine the association of hemoglobin levels with time-weighted means of renal function markers, such as fractional sodium excretion (FENa) and creatinine clearance (CrCl). Stratified by baseline hemoglobin level (<4.5, 4.5-6, or >6 mmol/L), these markers were modeled over time using a generalized linear mixed-effects model. All models were adjusted for potential confounders. Until a hemoglobin level of around 5 mmol/L was reached, increasing hemoglobin levels were associated with superior FENa and CrCl. Thereafter, this association plateaued. When hemoglobin levels were categorized, hemoglobin <4.5 mmol/L was associated with worse renal function. Hemoglobin levels were neither significantly associated with proteinuria during NMP nor with ATP levels at the end of NMP. Hemoglobin levels >6 mmol/L showed no additional benefits in renal function. In conclusion, we found an association between baseline hemoglobin levels and superior renal function parameters, but not injury, during NMP of porcine kidneys. Furthermore, we show that performing a retrospective cohort study of preclinical data is feasible and able to answer additional questions, reducing the potential use of laboratory animals.

Financial impact of donation after circulatory death heart transplantation: A single-center analysis.

Clinical success of donation after circulatory death (DCD) heart transplantation is leading to growing adoption of this technique. In comparison to procurement from a brain-dead donor, DCD requires additional resources. The economic impact of DCD heart transplantation from the hospital perspective is not well known. We compared the financial data of patients who received DCD allografts to those who received a DBD organ at our institution from January 1, 2021 to December 31, 2022. We also compared the cost of ex-situ machine perfusion to in-situ organ perfusion employed during DCD recovery. We performed 58 DBD and 22 DCD heart-alone transplantations during the study period. Out of 22 DCD grafts, 16 were recovered with thoracoabdominal normothermic regional perfusion (TA-NRP) and six with direct procurement followed by normothermic machine perfusion (DP-NMP). The contribution margin per case for DBD versus DCD was $234,362 and $235,440 (P=.72). The direct costs did not significantly differ between the two groups ($171,949 and 186,250; P=.49). In comparing the two methods of procuring hearts from DCD donors, the direct cost of TA-NRP was $155,955 in comparison to $223,399 for DP-NMP (P=.21). This difference translated into a clinically meaningful but not statistically significant greater contribution margin for TA-NRP ($242, 657vs. $175,768; P=.34). Our data showed that the adoption of DCD procurement did not have a negative financial impact on the contribution margin in our institution. Programs considering starting DCD heart transplantation, and those who are currently performing DCD procurement should evaluate their own financial situation.

Real-time monitoring of mitochondrial oxygenation during machine perfusion using resonance Raman spectroscopy predicts organ function

Organ transplantation is a life-saving procedure affecting over 100,000 people on the transplant waitlist. Ischemia reperfusion injury (IRI) is a major challenge in the field as it can cause post-transplantation complications and limit the use of organs from extended criteria donors. Machine perfusion technology has the potential to mitigate IRI; however, it currently fails to achieve its full potential due to a lack of highly sensitive and specific assays to assess organ quality during perfusion. We developed a real-time and non-invasive method of assessing organs during perfusion based on mitochondrial function and injury using resonance Raman spectroscopy. It uses a 441 nm laser and a high-resolution spectrometer to quantify the oxidation state of mitochondrial cytochromes during perfusion. This index of mitochondrial oxidation, or 3RMR, was used to understand differences in mitochondrial recovery of cold ischemic rodent livers during machine perfusion at normothermic temperatures with an acellular versus cellular perfusate. Measurement of the mitochondrial oxidation revealed that there was no difference in 3RMR of fresh livers as a function of normothermic perfusion when comparing acellular versus cellular-based perfusates. However, following 24 h of static cold storage, 3RMR returned to baseline faster with a cellular-based perfusate, yet 3RMR progressively increased during perfusion, indicating injury may develop over time. Thus, this study emphasizes the need for further refinement of a reoxygenation strategy during normothermic machine perfusion that considers cold ischemia durations, gradual recovery/rewarming, and risk of hemolysis.

Incorporating a hemodialysis filter into a commercial normothermic perfusion system to facilitate long-term preservation of human split-livers.

Normothermic machine perfusion (NMP) allows for the assessment and resuscitation of ex-vivo human livers prior to transplantation. Commercially available NMP systems are closed circuits that accumulate metabolic waste and cytokines over time, potentially limiting organ preservation times. Dialysis has been proposed as a method to remove waste and excess fluid from such systems. This study aimed to demonstrate the utility of integrating dialysis into a commercially available system by quantifying solute removal. A dialysis filter was attached in parallel to a commercially available liver perfusion system. Three livers declined for transplantation were split before undergoing long-term NMP with blood using the modified system. During perfusion, dialysate flow rates were set in the range of 100-600 mL/h for short periods of time. At each flow rate, perfusate and spent dialysate samples were collected and analyzed for solute clearance. The addition of dialysis to a commercial NMP system removed water-soluble waste and helped regulate electrolyte concentrations. Interleukin-6 was successfully removed from the perfusate. Solute clearance was proportional to dialysate flow rate. A guide for our perfusion setup was created for the appropriate selection of dialysis flow rates and duration based on real-time perfusate composition. Dialysis circuits can efficiently remove waste and regulate perfusate composition, and can be easily incorporated to improve the performance of commercially available systems. Quantification of the effect of dialysis on perfusate composition enables refined dialysis control to optimize electrolyte profiles and avoid the over- or under-correction of key solutes.

O197: Quality Assessment of Human Kidneys by Ex-vivo Normothermic Machine Perfusion prior to Transplantation

Abstract Introduction Ex-vivo normothermic machine perfusion (NMP) is a technique of preservation that can be used to assess the quality and suitability of a kidney for transplantation. This may prevent the unnecessary discard and increase the number of transplanted kidneys. Methods A total of 22 kidneys declined for transplant by all UK transplant centres, were assessed over a three-year period across three centres in the UK. Prior to NMP, most kidneys were declined due to poor quality cold flushing at retrieval. All kidneys were assessed during 1h of NMP. A quality assessment score (QAS) based on the appearance, blood flow and urine output was applied to each kidney. Scores ranged from 1 (best) to 5 (worst). Results Sixteen kidneys (72%) had a QAS of 1 to 3 and were transplanted into matched recipients. One patient died with a non-functioning kidney 12 days post-transplant due to a cardiac arrest. Six recipients (37.5%) had delayed graft function. The mean serum creatinine levels and estimated glomerular filtration rate at 3 months was 154±74µmol/L and 45±15mL/min/1.73m2, respectively. Graft and patient survival at 12 months were 94%. Of the 6 non-transplanted kidneys, 3 were deemed unsuitable after assessment during NMP, 1 was not transplanted due to logistical reasons and a prolonged cold ischaemic time, and the remaining 2 due to chronic degenerative changes assessed by histology scores. Conclusion This clinical research study demonstrated the ability to use NMP technology to successfully increase the number of transplants by assessing kidneys that would otherwise be discarded.