Based on the continuous increase of donor risk, with a majority of organs classified as marginal, quality assessment and prediction of liver function is of utmost importance. This is also caused by the notoriously lack of effective replacement of a failing liver by a device or intensive care treatment. While various parameters of liver function and injury are well-known from clinical practice, the majority of specific tests require prolonged diagnostic time and are more difficult to assess ex situ. In addition, viability assessment of procured organs needs time, because the development of the full picture of cellular injury and the initiation of repair processes depends on metabolic active tissue and reoxygenation with full blood over several hours or days. Measuring injury during cold storage preservation is therefore unlikely to predict the viability after transplantation. In contrast, dynamic organ preservation strategies offer a great opportunity to assess organs before implantation through analysis of recirculating perfusates, bile and perfused liver tissue. Accordingly, several parameters targeting hepatocyte or cholangiocyte function or metabolism have been recently suggested as potential viability tests before organ transplantation. We summarize here a current status of respective machine perfusion tests, and report their clinical relevance.

Although machine perfusion is a hot topic today, we are just at the beginning of understanding the underlying mechanisms of protection. Recently, the first randomized controlled trial reported a significant reduction of ischemic cholangiopathies after transplantation of livers donated after circulatory death, provided the grafts were treated with an endischemic hypothermic oxygenated perfusion (HOPE). This approach has been known for more than fifty years, and was initially mainly used to preserve kidneys before implantation. Today there is an increasing interest in this and other dynamic preservation technologies and various centers have tested different approaches in clinical trials and cohort studies. Based on this, there is a need for uniform perfusion settings (perfusion route and duration), and the development of general guidelines regarding the duration of cold storage in context of the overall donor risk is also required to better compare various trial results. This article will highlight how cold perfusion protects organs mechanistically, and target such technical challenges with the perfusion setting. Finally, the options for viability testing during hypothermic perfusion will be discussed.

Background: Organ perfusion technology is increasingly used in many countries, with a focus, however, on the Western world. This study investigates the current international trends and obstacles to the broader routine implementation of dynamic perfusion concepts in liver transplantation. Methods: A web-based anonymous survey was launched in 2021. Experts of all involved specializations from 70 centers in 34 countries were contacted, based on the published literature and experience in the field of abdominal organ perfusion. Results: Overall, 143 participants from 23 countries completed the survey. Most respondents were male (67.8%) and transplant surgeons (64.3%) working at university hospitals (67.9%). The majority had experience with organ perfusion (82%), applying mainly hypothermic machine perfusion (HMP; 38%) and other concepts. While most (94.4%) expect a higher utilization of marginal organs with machine perfusion, the majority considers HMP the best technique to reduce liver discard-rates. While most respondents (90%) believed machine perfusion should be fully commissioned, the lack of funding (34%) and knowledge (16%) as well as limited staff (19%) were the three main obstacles to a routine clinical implementation. Conclusion: Although dynamic preservation concepts are increasingly used in clinical practice, significant challenges remain. Specific financial pathways, uniform regulations, and tight collaborations among involved experts are needed to achieve wider global clinical use.

Ex situ machine perfusion has emerged as a pivotal technique for organ preservation and pre-transplant viability assessment, where the real-time monitoring of mitochondrial biomarkers—flavin mononucleotide (FMN) and nicotinamide adenine dinucleotide (NADH)—could significantly mitigate ischemia-reperfusion injury risks. This study develops a non-invasive optical method combining fluorescence and UV-visible spectrophotometry to quantify FMN and NADH in hypothermic oxygenated perfusion media. Calibration curves revealed linear responses for both biomarkers in absorption and fluorescence (FMN: λ_ex = 445 nm, λ_em = 530–540 nm; NADH: λ_ex = 340 nm, λ_em = 465 nm) at concentrations < 100 μg mL⁻¹. However, NADH exhibited nonlinear fluorescence above 100 μg mL⁻¹, requiring shifted excitation to 365 nm for reliable detection. Spectroscopic analysis further demonstrated how perfusion solution composition alters FMN/NADH fluorescence properties, with consistent reproducibility across media. The method’s robustness was validated through comparative studies in clinically relevant solutions, proposing a strategy for precise biomarker quantification without invasive sampling. These findings establish a foundation for real-time, optical biosensor development to enhance organ perfusion monitoring. By bridging spectroscopic principles with clinical needs, this work advances translational sensor technologies for transplant medicine, offering a template for future device integration.

Background/Objectives: The use of extended-criteria donors (ECDs) is rapidly increasing, with higher risks for impaired outcomes after liver transplantation (LT). Normothermic machine perfusion (NMP) can enhance graft viability assessment, though lactate clearance as a viability marker lacks consensus in clinical practice. Methods: This study analyzed 213 adult liver transplants using NMP from October 2022 to January 2024. Perfusate lactate levels were measured with an Epoc^® reader and five lactate-based viability criteria were evaluated for predicting post-LT outcomes. Results: All livers cleared lactate at 6 h of NMP (median 0.51 mmol/L). However, 33 livers failed at least one lactate viability criterion. Thirteen livers (6.1%) were discarded based on traditional criteria, but discard rates would have been higher using Groningen (14.6%) or Brisbane (11.2%) criteria for lactate. Outcomes for the recipients of livers that failed the lactate criteria were comparable to those of recipients with livers meeting all criteria, including biliary complications (p = 0.63), graft survival (>0.99), and 6-month CCI (p = 0.89). ROC analysis revealed poor predictive value for graft survival for lactate clearance criteria (AUC 0.50), while lactate was outperformed by MEAF score (AUC 0.67). Conclusions: Lactate clearance alone does not predict outcomes, highlighting the need for further validation of alternative viability.

Background/Objectives: Hypothermic oxygenated perfusion (HOPE) improves graft preservation in whole liver transplantation, yet evidence supporting its use in split grafts for pediatric transplantation remains limited. Mitochondrial injury assessed during HOPE through spectroscopic measurement of flavin mononucleotide (FMN) has been associated with graft function in whole-organ transplantation. Here, we evaluate a human liver assessment pathway integrating mitochondrial viability testing with ex situ liver splitting during HOPE. Methods: Following standard procurement and transport, twelve discarded extended criteria human donor livers were evaluated for split feasibility and underwent HOPE (VitaSmart^®). Donors were between 40 and 72 years with a BMI of 23.4–42.7 kg/m² and 4–22 h of cold storage prior to HOPE. After two hours of portal-venous HOPE treatment, different split procedures were performed. Perfusates and tissues were analyzed for mitochondrial injury and inflammatory responses. Results: Four grafts met previously reported FMN thresholds for transplant suitability in whole-graft HOPE studies (FMN ≤ 0.02 μg/mL at 60 min). Livers with low FMN release demonstrated lower Complex I and II injury, greater ATP recovery, and reduced inflammatory signaling during HOPE. Conclusions: These findings indicate that mitochondrial injury during HOPE can be monitored during ex situ splitting and suggest that FMN-guided metabolic assessment may support graft evaluation within split liver transplantation pathways for pediatric recipients.