Hours Of Normothermic Machine Perfusion Research Articles

Continuous Renal Replacement Therapy During Long-term Normothermic Machine Perfusion of Human Donor Livers for up to 7 D

Background. Normothermic machine perfusion (NMP) is used to preserve and test donor livers before transplantation. During NMP, the liver is metabolically active and produces waste products, which are released into the perfusate. In this study, we describe our simplified and inexpensive setup that integrates continuous renal replacement therapy (CRRT) with NMP for up to 7 d. We also investigated if the ultrafiltrate could be used for monitoring perfusate concentrations of small molecules such as glucose and lactate. Methods. Perfusate composition (urea, osmolarity, sodium, potassium, chloride, calcium, magnesium, phosphate, glucose, and lactate) was analyzed from 56 human NMP procedures without CRRT. Next, in 6 discarded human donor livers, CRRT was performed during NMP by integrating a small dialysis filter (0.2 m2) into the circuit to achieve continuous ultrafiltration combined with continuous fluid substitution for up to 7 d. Results. Within a few hours of NMP without CRRT, a linear increase in osmolarity and concentrations of urea and phosphate to supraphysiological levels was observed. After integration of CRRT into the NMP circuit, the composition of the perfusate was corrected to physiological values within 12 h, and this homeostasis was maintained during NMP for up to 7 d. Glucose and lactate levels, as measured in the CRRT ultrafiltrate, were strongly correlated with perfusate levels (r = 0.997, P < 0.001 and r = 0.999, P < 0.001, respectively). Conclusions. The integration of CRRT into the NMP system corrected the composition of the perfusate to near-physiological values, which could be maintained for up to 7 d. The ultrafiltrate can serve as an alternative to the perfusate to monitor concentrations of small molecules without potentially compromising sterility.

Sequential hypothermic and normothermic perfusion preservation and transplantation of expanded criteria donor livers

BackgroundThe purpose of this study was to assess the safety and feasibility of sequential hypothermic oxygenated perfusion and normothermic machine perfusion and the potential benefits of graft viability preservation and assessment before liver transplantation. MethodsWith the Food and Drug Administration and institutional review board approval, 17 expanded criteria donor livers underwent sequential hypothermic oxygenated perfusion and normothermic machine perfusion using our institutionally developed perfusion device. ResultsExpanded criteria donor livers were from older donors, donors after cardiac death, with steatosis, hypertransaminasemia, or calcified arteries. Perfusion duration ranged between 1 and 2 hours for the hypothermic oxygenated perfusion phase and between 4 and 9 hours for the normothermic machine perfusion phase. Three livers were judged to be untransplantable during normothermic machine perfusion based on perfusate lactate, bile production, and macro-appearance. One liver was not transplanted because of recipient issue after anesthesia induction and failed reallocation. Thirteen livers were transplanted, including 9 donors after cardiac death livers (donor warm ischemia time 16–25 minutes) and 4 from donors after brain death. All livers had the standardized lactate clearance >60% (perfusate lactate cleared to <4.0 mmol/L) within 3 hours of normothermic machine perfusion. Bile production rate was 0.2 to 10.7 mL/h for donors after brain death livers and 0.3 to 6.1 mL/h for donors after cardiac death livers. After transplantation, 5 cases had early allograft dysfunction (3 donors after cardiac death and 2 donors after brain death livers). No graft failure or patient death has occurred during follow-up time of 6 to 13 months. Two livers developed ischemic cholangiopathy. Compared with our previous normothermic machine perfusion study, the bile duct had fewer inflammatory cells in histology, but the post-transplant outcomes had no difference. ConclusionSequential hypothermic oxygenated perfusion and normothermic machine perfusion preservation is safe and feasible and has the potential benefits of preserving and evaluating expanded criteria donor livers.

344.3: Extracellular Vesicles Released During Normothermic Machine Perfusion Are Associated With Human Donor Kidney Characteristics

Background: Extracellular Vesicles (EVs) represent stable, tissue specific nano-sized particles that reflect the conditional state of their tissue of origin. Here, the dynamic release and phenotype of kidney EVs was characterized and quantified during Normothermic Machine Perfusion (NMP) of Expanded-Criteria Donor (ECD) kidneys to examine whether EVs could function as a potential biomarker for assessing kidney quality before transplantation. Materials & Methods: Eight discarded ECD kidneys (~13 ± 5 hours of cold ischemia, age 68 ± 7 (mean ± standard deviation), all male) were perfused in a closed system at 37 0C for 6 hours. Perfusates were taken before and at 1, 3 and 6 hours of NMP and examined with Nanoparticle Tracking Analysis (NTA) and Imaging Flow Cytometry (IFCM). For IFCM, perfusates were stained with the tetraspanins CD9, CD63 or CD81 (general EV markers), or a mix of these three markers in combination with CFDA-SE (a non-fluorescent molecule that acquires fluorescent properties after cleavage by intravesicular esterases) to identify, quantify and characterize EVs. Results: Analysis of perfusates with NTA revealed that the majority of nanoparticles present in the perfusates are <300 nm. For CFSE and the mix of tetraspanin double-positive EVs, we observed a ~700/ 740/ 560 fold increase compared to EV levels before perfusion at 1, 3 and 6 hours of NMP, respectively. Analysis of EV concentrations with crude donor characteristics (e.g. age, cold ischemia time (CIT), kidney weight) and NMP viability characteristics (renal flow, renal flow resistance, urine production) revealed that double-positive EV are negatively correlated with CIT whilst positive correlations were found with donor age after the first hour of NMP. Furthermore, tetraspanin CD81 was found to represent the majority (~75%) of the excreted double-positive EV (CD9: ~16%/ CD63 ~8%) (Figure). Conclusion: EVs <300 nm are released by ECD kidneys during NMP with highest excretion levels during the first hour of perfusion. Tetraspanin CD81 is predominantly present on these EVs, and EV concentrations were shown to be correlated with well-established indicators of kidney quality such as donor age and CIT. The characterization of the excreted EVs as well as their correlation with clinical parameters provide a starting point to study their role as potential biomarkers of kidney quality.

Utilization of dielectric properties for assessment of liver ischemia-reperfusion injury in vivo and during machine perfusion

There is a shortage of donor livers and patients consequently die on waiting lists worldwide. Livers are discarded if they are clinically judged to have a high risk of non-function following transplantation. With the aim of extending the pool of available donor livers, we assessed the condition of porcine livers by monitoring the microwave dielectric properties. A total of 21 livers were divided into three groups: control with no injury (CON), biliary injury by hepatic artery occlusion (AHEP), and overall hepatic injury by static cold storage (SCS). All were monitored for four hours in vivo, followed by ex vivo plurithermic machine perfusion (PMP). Permittivity data was modeled with a two-pole Cole–Cole equation, and dielectric properties from one-hour intervals were analyzed during in vivo and normothermic machine perfusion (NMP). A clear increasing trend in the conductivity was observed in vivo in the AHEP livers compared to the control livers. After four hours of NMP, separations in the conductivity were observed between the three groups. Our results indicate that dielectric relaxation spectroscopy (DRS) can be used to detect and differentiate liver injuries, opening for a standardized and reliable point of evaluation for livers prior to transplantation.

Gene expression correlation analysis of livers undergoing normothermic machine perfusion identifies interactions between donor demographics and liver function

BackgroundLiver transplantation is currently the only cure for end‐stage liver disease, but the shortage of donor livers severely limits the effectiveness of transplantation. This shortage is made worse by challenges in preserving and assessing livers pre‐transplant that can result in discarding of functional livers. Normothermic machine perfusion (NMP) is a method of liver preservation that aims to provide physiological conditions while allowing real‐time assessment of transplant viability criteria. The aim of this study was to understand the effect of machine perfusion on the transcriptome and to correlate changes in gene expression with functional liver metrics.MethodsTen discarded livers (5 steatotic, 5 non‐steatotic), rejected by local transplant centers, were obtained from donation after circulatory death (DCD). The livers underwent 12 hours of NMP with oxygenated red blood cells. Serial tissue and plasma samples were collected at various times during perfusion. Plasma lactate samples were used to categorize liver as meeting viability criteria (viable) or not (nonviable) following NMP. Transcriptome sequencing was performed on serial biopsies taken at 0, 3, and 6hr during perfusion. Weighted gene co‐expression network analysis (WGCNA) was performed to correlate each module with demographics and functional metrics. Pathway and transcription factor analysis were performed on significant modules of interest.ResultsExpression data at 0, 3 and 6 hr of perfusion was used to construct the weighted co‐expression network. Gene co‐expression modules were then correlated with various clinical demographics and functional data collected during NMP. To evaluate the functional association of genes in the modules that significantly correlated with arterial lactate levels, we performed Gene Ontology enrichment analysis. By using lactate clearance as an indicator of transplant viability we were able to identify co‐expression gene sets enriched for biological processes including drug metabolism, immune response, autophagy, vascular development, nutrient metabolism, and gene expression.ConclusionsCurrent donor liver assessment models are limited by traditionally accessible parameters and can often lead to discarding potentially viable organs. NMP provides a novel data collection platform that could be used to improve traditional assessment models. By performing WGCNA, we were able to capitalize on an extensive set of metrics to identify interactions between the diverse donor demographics, the functional data collected during NMP and changes in gene expression. This may ultimately allow us to identify novel biomarkers to improve our current methods of donor liver assessment and assist the development of targeted therapeutics for more successful preservation and utilization of diverse donor livers.

Development of ex vivo normothermic perfusion as an innovative method to assess pancreases after preservation

Ann Ogbemudia, Julien Branchereau (Joint first authors), Gabriella Hakim, Fungai Dengu, FaysalEl-Gilani, John Mulvey, Kaithlyn Rozenberg, Thomas Prudhomme, Letizia Lo Faro, James Hunter,Paul Johnson, Rutger Ploeg and Peter Friend&#x0D; &#x0D; Objective Static cold storage (SCS) is the standard method for pancreas preservation but does not facilitate objective organ assessment prior to transplantation. Normothermic machine perfusion (NMP) has been used to test other abdominal and thoracic organs’ function and viability in transplantation settings. Our aim was to develop a NMP protocol specific for pancreases and then investigate its potential as an organ assessment strategy.&#x0D; Method 8 porcine pancreases were procured in conditions replicating donation after circulatory death with warm ischaemia time of 25 minutes. After 3 hours of static cold storage (SCS) the pancreases were divided into 3 experimental groups 1) the feasibility group (n=2) that underwent 2.5 hours of NMP 2) the SCS group (n = 2) that underwent an additional 6 hours of SCS prior to assessment on NMP for an hour and 3) the Oxygenated Hypothermic Machine Perfusion (oxyHMP) group (n = 4) that underwent 6 hours of oxyHMP followed by 1-hour assessment on NMP. The NMP protocol used autologous, leucodepleted blood delivered at a mean arterial pressure of 40mmHg with a temperature of 37oC. At timed intervals during NMP, perfusate samples were collected for gas analysis and perfusion parameters were recorded.&#x0D; Results The feasibility group was used to develop the NMP protocol and demonstrated stable perfusion parameters throughout NMP. Compared to the SCS group the oxyHMP group demonstrated better average perfusion characteristics with lower resistances, higher flow rates, lower mean lactate levels and physiological pH. The oxyHMP group maintained normal macroscopic appearances during NMP. At the end of NMP the SCS group had an average 32% weight increase compared to the oxyHMP group that were found to have a 17% weight reduction.&#x0D; Conclusion Normothermic machine perfusion of whole pancreases is feasible after cold preservation and potentially useful as an assessment strategy. Furthermore, it demonstrated that oxygenated HMP may be beneficial for pancreas preservation compared to SCS.

Abstract 1369: Predicting clinical pharmacokinetics and toxicity of current and emerging oncology therapeutics by normothermic perfusion of isolated human-sized organs

Abstract Novel cancer therapeutics have less than a 12% probability of translating from bench to bedside. Unwarranted toxicity and inadequate therapeutic delivery due to uptake by clearance organs, not predicted by current preclinical methods, have contributed towards this high rate of attrition. In the present work, we propose normothermic machine perfusion of human or human-sized organs as a more predictive, closer-to-human model to investigate drug pharmacokinetics and toxicity. Over the past decade, developments in the field of organ preservation for transplantation have enabled prolonged (&amp;gt;12 hours) normothermic machine perfusion (NMP) of isolated porcine or human organs ex vivo, maintaining quasi-physiological haemodynamic, synthetic and metabolic function using a packed red cell perfusate with physiological oxygenation and nutrient levels at normal body temperature. This preserves physiological processes such as metabolism and drug elimination, and enables easy access to tissue, blood and excreted biological fluids, with NMP livers producing bile and NMP kidneys producing urine. We hypothesise that this will provide a physiologically relevant platform to investigate drug pharmacokinetics and toxicity. We selected a widely used small-molecule chemotherapeutic (Irinotecan hydrochloride 2mg/ml, Medac, UK) which has seen decades of clinical use and benefits from extensive clinical pharmacokinetic data. The small-molecule drug was infused into isolated porcine and human livers and kidneys, with quantification of concentration time profiles of the prodrug and its main metabolites in plasma, bile and urine over 16-24 hours of NMP. In addition to irinotecan (CPT11), three of its metabolites (APC, SN38G, SN38) were successfully detected and quantified, demonstrating peak plasma concentrations (Cmax ~ 10,000 ng/mL, 1000 ng/mL, 100 ng/g, 30 ng/g), plasma decay rates and percentages of injected dose in bile (%ID ~20%, 8%, 25%, 1%) and urine (%ID ~20%, 0.06%, 0.5%,0.1%) that are comparable to clinical data. Drug-tissue toxicity could also be adequately replicated in the NMP model. In conclusion, we have demonstrated that human-sized isolated, normothermically perfused livers and kidneys accurately represent the clinically observed pharmacokinetic and toxicity profiles of an established small-molecule therapeutic. Further model validation is ongoing for biologics and other nanomedicines which are susceptible to clearance by the mononuclear phagocytic system or are hepato- or nephrotoxic. If this proves successful, normothermic machine perfusion of isolated porcine and human organs could greatly aid the early screening of candidate therapeutics and significantly enhance the pace and success rate with which they are translated into patients. Citation Format: Tamsyn Clark, Luca Bau, Fungai Dengu, Daniel Voyce, Robert Carlisle, Peter Friend, Constantin Coussios. Predicting clinical pharmacokinetics and toxicity of current and emerging oncology therapeutics by normothermic perfusion of isolated human-sized organs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1369.

Ex vivo delivery of Mirococept: A dose-finding study in pig kidney after showing a low dose is insufficient to reduce delayed graft function in human kidney.

The complement system plays a pivotal role in the pathogenesis of ischemia-reperfusion injury in solid organ transplantation. Mirococept is a potent membrane-localizing complement inhibitor that can be administered ex vivo to the donor kidney prior to transplantation. To evaluate the efficacy of Mirococept in reducing delayed graft function (DGF) in deceased donor renal transplantation, we undertook the efficacy of mirococept (APT070) for preventing ischaemia-reperfusion injury in the kidney allograft (EMPIRIKAL) trial (ISRCTN49958194). A dose range of 5-25mg would be tested, starting with 10mg in cohort 1. No significant difference between Mirococept at 10mg and control was detected; hence the study was stopped to enable a further dose saturation study in a porcine kidney model. The optimal dose of Mirococept in pig kidney was 80mg. This dose did not induce any additional histological damage compared to controls or after a subsequent 3hours of normothermic machine perfusion. The amount of unbound Mirococept postperfusion was found to be within the systemic dose range considered safe in the Phase I trial. The ex vivo administration of Mirococept is a safe and feasible approach to treat DGF in deceased donor kidney transplantation. The porcine kidney study identified an optimal dose of 80mg (equivalent to 120mg in human kidney) that provides a basis for further clinical development.

Increasing metformin concentrations and its excretion in both rat and porcine ex vivo normothermic kidney perfusion model

IntroductionMetformin can accumulate and cause lactic acidosis in patients with renal insufficiency. Metformin is known to inhibit mitochondria, while renal secretion of the drug by proximal tubules indirectly requires energy....

Metformin Preconditioning and Postconditioning to Reduce Ischemia Reperfusion Injury in an Isolated Ex Vivo Rat and Porcine Kidney Normothermic Machine Perfusion Model.

Metformin may act renoprotective prior to kidney transplantation by reducing ischemia‐reperfusion injury (IRI). This study examined whether metformin preconditioning and postconditioning during ex vivo normothermic machine perfusion (NMP) of rat and porcine kidneys affect IRI. In the rat study, saline or 300 mg/kg metformin was administered orally twice on the day before nephrectomy. After 15 minutes of warm ischemia, kidneys were preserved with static cold storage for 24 hours. Thereafter, 90 minutes of NMP was performed with the addition of saline or metformin (30 or 300 mg/L). In the porcine study, after 30 minutes of warm ischemia, kidneys were preserved for 3 hours with oxygenated hypothermic machine perfusion. Subsequently, increasing doses of metformin were added during 4 hours of NMP. Metformin preconditioning of rat kidneys led to decreased injury perfusate biomarkers and reduced proteinuria. Postconditioning of rat kidneys resulted, dose‐dependently, in less tubular cell necrosis and vacuolation. Heat shock protein 70 expression was increased in metformin‐treated porcine kidneys. In all studies, creatinine clearance was not affected. In conclusion, both metformin preconditioning and postconditioning can be done safely and improved rat and porcine kidney quality. Because the effects are minor, it is unknown which strategy might result in improved organ quality after transplantation.

Clearance of transaminases during normothermic ex situ liver perfusion.

BackgroundOne of the most promising applications of liver normothermic machine perfusion (NMP) is the potential to directly assess graft viability and injury. In most NMP studies, perfusate transaminases are utilized as markers of graft injury. Our aim was to further elucidate the metabolism of transaminases by healthy porcine livers during NMP, specifically whether such livers could clear circuit perfusate transaminases.MethodsA highly concentrated transaminase solution was prepared from homogenized liver, with an aspartate aminotransferase (AST) level of 107,427 U/L. Three livers in the treatment group were compared to three controls, during 48 hours of NMP. In the treatment group, the circuit perfusate was injected with the transaminase solution to artificially raise the AST level to a target of 7,500 U/L. Perfusate samples were taken at two-hour intervals and analyzed for biochemistry until NMP end. Graft oxygen consumption and vascular parameters were monitored.ResultsCompared to controls, treated perfusions demonstrated abrupt elevations in transaminase levels (p>0.0001) and lactate dehydrogenase (LDH) (p>0.0001), which decreased over time, but never to control baseline. Liver function, as demonstrated by lactate clearance and oxygen consumption was not different between groups. The treatment group demonstrated a higher portal vein resistance (p = 0.0003), however hepatic artery resistance was similar. Treated livers had higher bile production overall (p<0.0001).ConclusionsAddition of high levels of transaminases and LDH to a healthy porcine liver during ex situ perfusion results in progressive clearance of these enzymes, suggesting preserved liver metabolism. Such tolerance tests may provide valuable indicators of prospective graft function.

Combination of hypothermic oxygenated machine perfusion followed by normothermic machine perfusion optimises the reconditioning of marginal human donor livers

Background: The shortage of organs for transplantation requires acceptance of livers from marginal donors. Hypothermic oxygenated machine perfusion (HOPE) improves mitochondrial function decreasing oxidative injury during reperfusion. Normothermic machine perfusion (NMP) allows viability assessment and extended preservation. We aim to assess whether a combination of both techniques would merge benefits and increase the rescue rate of marginal organs. Methods: Ten discarded human livers were randomly allocated to two experimental groups: (1) NMP group, in which 5 organs were perfused at 37oC using an acellular oxygen carrier based perfusate for 6 hours; (2) HOPE+NMP group, in which 5 organs had 2 hours of HOPE at 10oC followed by 4 hours of NMP. Viability was assessed at the end of 6 hours perfusion using the lactate clearance criteria. Results: The HOPE phase decreased the mitochondria respiratory rate (oxygen uptake, p=0.043; pCO2 in the perfusate, p=0.040) and increased the median ATP content (p=0.016). This resulted in slower oxygen consumption during rewarming and decreased tissue expression of markers of oxidative injury (4-hydroxynonenal, p=0.008) and activation of the inflammatory cascade (Kupffer cells, p=0.016; Vascular Cell Adhesion Protein 1, p=0.050). Livers deemed non-viable at the end of the NMP had lower ATP levels (p=0.050) and higher lactate levels (p=0.020). All HOPE+NMP group livers were deemed viable compared with three (60%) in the NMP alone group (p=0.222). Conclusion: The combined protocol of HOPE+NMP together merged benefits of the techniques and increased the rescue rate of marginal livers into the pool of transplantable organs compared with NMP alone.

Lipid metabolism and functional assessment of discarded human livers with steatosis undergoing 24 hours of normothermic machine perfusion.

Normothermic machine perfusion (NMP) is an emerging technology to preserve liver allografts more effectively than cold storage (CS). However, little is known about the effect of NMP on steatosis and the markers indicative of hepatic quality during NMP. To address these points, we perfused 10 discarded human livers with oxygenated NMP for 24 hours after 4-6 hours of CS. All livers had a variable degree of steatosis at baseline. The perfusate consisted of packed red blood cells and fresh frozen plasma. Perfusate analysis showed an increase in triglyceride levels from the 1st hour (median, 127 mg/dL; interquartile range [IQR], 95-149 mg/dL) to 24th hour of perfusion (median, 203 mg/dL; IQR, 171-304 mg/dL; P = 0.004), but tissue steatosis did not decrease. Five livers produced a significant amount of bile (≥5 mL/hour) consistently throughout 24 hours of NMP. Lactate in the perfusate cleared to <3 mmol/L in most livers within 4-8 hours of NMP, which was independent of bile production rate. This is the first study to characterize the lipid profile and functional assessment of discarded human livers at 24 hours of NMP. Liver Transplantation 24 233-245 2018 AASLD.

Pre- and postconditioning effects of metformin in rat donor livers

Background: Pre- or reconditioning of donor livers can improve organ quality prior to transplantation. The aim of this study was to investigate whether metformin as pre- or reconditioning agent is able to reduce preservation injury in rat donor livers and improve hepatobiliary function during ex situ normothermic machine perfusion (NMP). Methods: To study the preconditioning effects of metformin, metformin was administered via oral gavage 12 and 2 hours before the hepatectomy. To assess the reconditioning effects of metformin, in 2 other groups, metformin was added to the NMP perfusion fluid in two different concentrations (30 and 300 mg/L). In the reference group, no pre- or reconditioning was carried out. In all groups, rat donor livers were preserved for 4 hours in preservation fluid on melting ice. Thereafter, NMP was performed for viability assessment. Results: Preconditioning improved ATP production and hepatobiliary function (assessed by total bile production, biliary bilirubin and bicarbonate) and significantly lowered levels of lactate and glucose during NMP. On the other hand, metformin preconditioning did not reduce markers for hepatobiliary injury such as AST, ALT, LDH, caspase-3 activity, TBARS or biliary gamma-GT and LDH. Reconditioning with metformin did not improve hepatobiliary function or reduce injury markers during NMP. Conclusion: Preconditioning of rat donor livers with metformin improves hepatobiliary function but does not reduce preservation injury as assessed during 3 hours of NMP. Reconditioning with metformin showed no beneficial effects.

(472) - The Interleukin 4 Receptor-α Potentiates the Effect of Oncostatin M Receptor on the Release of FGF23 by Cardiomyocytes

are combined, there are concerns regarding delays to institution of liver cold preservation. The aim of this study was to develop a combined DCD heart and liver retrieval protocol in a pig model with subsequent normothermic machine perfusion (NMP) of both organs to mitigate warm ischemic damage. Methods: Pigs (n= 12; 60-70 kg) were anesthetised. Baseline observations were recorded. After sternotomy, and laparotomy, ventilatory support was withdrawn to mimic DCD conditions. Death was defined as equalisation of central venous and mean arterial pressures. After a 5-minute standoff period, 1.5-2 L blood was collected from a right atrial cannula then a cardiac preservation flush (4°C) commenced via the proximal ascending aorta. The inferior vena cava was cut to vent the organs. The thoracic cavity was kept cold with saline ice slush. The heart was explanted and prepared on back-table for NMP. Liver preservation was begun immediately after blood collection by cold preservation solution flush via the infra-renal aorta and portal vein. The hepatic artery, portal vein and common bile duct were transected, and the liver explanted for back-table NMP preparation. Results: Warm ischaemic time (WIT) and back-table time (BTT) was 21 + 5 and 29 + 6 min for the heart; 20 + 6 (commencement of flush) and 33 + 19 min for the liver. The average blood volume collected was 1.6 L: 1:1 dilution with Krebs resulted in significant hemodilution (from 23 + 5% to 15 + 6%) and hypocalcemia (1.30 + 0.15 to 0.64 + 0.32 mM). This resulted in sub-optimal cardiac contractile recovery despite a favourable lactate profile. Liver enzyme release, bile production, and lactate and pH profiles were favourable during the first 4-6 hours of NMP but deteriorated thereafter. Conclusion: Heart and liver retrieval under standard DCD protocol is possible without excessively extending the WIT for either organ. However, there is insufficient donor blood to support NMP of both organs.

Sequential Cold Storage and Normothermic Perfusion of the Ischemic Rat Liver

Extending transplant criteria to include livers obtained from donors after cardiac death (DCD) could increase the liver donor pool, but conventional simple cold storage of these ischemic organs can lead to poor graft function after transplantation. Experimental normothermic machine perfusion has previously proven to be useful for the recovery and preservation of DCD livers, but it is more complicated than conventional cold storage, and, therefore, is perhaps not practical during the entire preservation period. In clinical situations, the combined use of simple cold storage and normothermic perfusion preservation of DCD livers might be more realistic, but even a brief period of cold storage prior to normothermic preservation has been suggested to have a negative impact on graft viability. In this study we show that rat livers subjected to 45 minutes of ex vivo warm ischemia followed by 2 hours of simple cold storage can be reclaimed by 4 hours of normothermic machine perfusion. These livers could be orthotopically transplanted into syngeneic recipients with 100% survival after 4 weeks (N = 10), similar to the survival of animals that received fresh livers that were stored on ice in University of Wisconsin (UW) solution for 6 hours (N = 6). On the other hand, rats that received ischemic livers preserved on ice in UW solution for 6 hours (N = 6) all died within 12 hours after transplantation. These results suggest that normothermic perfusion can be used to reclaim DCD livers subjected to an additional period of cold ischemia during hypothermic storage.