Hypothermic vs Normothermic Machine Perfusion in Liver Transplantation in the US: A Cohort Study

BACKGROUND: Machine perfusion in liver transplantation has allowed use of higher-risk donors (older age, higher macrosteatosis, or donation after circulatory death), with improved outcomes compared with static cold storage. Clinical outcomes between the most common machine perfusion modalities (hypothermic and normothermic) have not been reported. STUDY DESIGN: Adult deceased donor liver transplant recipients who received an allograft reported as machine perfused by the organ procurement organization were identified using 2016 to 2024 Organ Procurement and Transplantation Network data in the US. Machine perfusion was categorized as hypothermic (n = 235) or normothermic (n = 3,897). Risks of all-cause and death-censored graft loss were quantified using propensity-weighted Cox proportional hazard models by machine perfusion modality. RESULTS: Machine perfusion of transplanted livers increased 11-fold and 25-fold for hypothermic (2019: n = 9; 2024: n = 109) and normothermic (2019: n = 84; 2024: n = 2,167) perfusion. One-year adjusted risks of all-cause (adjusted hazard ratio 1.00, 95% CI 0.59 to 1.69, p = 0.99) and death-censored (adjusted hazard ratio 1.00, 95% CI 0.43 to 2.35, p = 1.0) graft loss were similar between the 2 machine perfusion types. Additionally, the cumulative incidences of primary nonfunction and hepatic artery thrombosis were similar among liver transplant recipients between hypothermic and normothermic machine perfusion. CONCLUSIONS: This report is the first direct comparison of outcomes among liver transplant recipients by machine perfusion modality. It demonstrates increased use of machine perfusion, and these preliminary findings suggest equivalent outcomes among liver transplant recipients with hypothermic and normothermic machine perfusion on a national level, although further study is needed.