Predictive value of early postoperative lactate (<6 h) during normothermic machine perfusion and outcome after liver transplantation: results from a multicentre study.

Background: Biomarkers with strong predictive capacity towards transplantation outcome for livers undergoing normothermic machine perfusion (NMP) are needed. We investigated lactate clearing capacity as a basic function of liver viability during the first 6 h of NMP.

Methods: A trial conducted in 6 high-volume transplant centres in Europe. All centres applied a back-to-base NMP approach with the OrganOx metra system. Perfusate lactate levels at start, 1, 2, 4 and 6 h of NMP were assessed individually and as area under the curve (AUC) and correlated with EAD (early allograft dysfunction), MEAF (model for early allograft function) and modified L-GrAFT (liver graft assessment following transplantation) scores.

Results: A total of 509 livers underwent ≥6 h of NMP before transplantation in 6 centres in the UK, Germany and Austria. The donor age was 53 (40-63) years (median, i.q.r.).The total NMP time was 10.8 (7.9-15.7) h. EAD occurred in 26%, MEAF was 4.72 (3.54-6.05) and L-GrAFT10 -0.96 (-1.52--0.32). Lactate at 1, 2 and 6 h correlated with increasing robustness with MEAF. Rather than a binary assessment with a cut-off value at 2 h, the actual 2 h lactate level correlated with the MEAF (P = 0.0306 versus P = 0.0002, Pearson r = 0.01087 versus r = 0.1734). The absolute lactate concentration at 6 h, the AUC of 0-6 h and 1-6 h (P < 0.0001, r = 0.3176) were the strongest predictors of MEAF.

Conclusion: Lactate measured 1-6 h and lactate levels at 6 h correlate strongly with risk of liver allograft dysfunction upon transplantation. The robustness of predicting MEAF by lactate increases with perfusion duration. Monitoring lactate levels should be extended to at least 6 h of NMP routinely to improve clinical outcome.