Assessing Lactate’s Role as a Predictor of Post-Transplant Outcomes During Normothermic Machine Perfusion

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.