Back-to-base Versus In-transit Machine Perfusion in Donation After Circulatory Death Liver Transplantation: Insights From a National Registry

Background. Normothermic machine perfusion (NMP) improves utilization of extended criteria liver grafts, but the optimal delivery strategy—whether in-transit or back-to-base—remains uncertain. Methods. Adult recipients of donation after circulatory death (DCD) liver transplants between January 1, 2022, and January 1, 2024, were identified using the national transplant database. In-transit NMP was defined as grafts coded as machine perfused; back-to-base NMP was inferred for noncoded grafts with a cold ischemia time of ≥10 h. Baseline characteristics, geographic distribution, and outcomes—including acute rejection, length of stay, and graft survival—were compared. Multivariable Cox regression was used to adjust for dialysis and recipient hospitalization status. A sensitivity analysis was performed, limited to cases with cold ischemia time of ≥10 h across both groups. Results. Among 1217 DCD liver transplants using NMP, 936 (77%) were in-transit and 281 (23%) were back-to-base. In-transit NMP was more commonly used in the Western United States, whereas back-to-base was concentrated in the Midwest and Southeast. In-transit recipients had higher rates of pretransplant dialysis (3.1% versus 0.7%; P < 0.05) and shorter preservation times (14.1 versus 16.0 h; P < 0.05). Median hospital stay was shorter in the in-transit group (8 versus 9 d, P < 0.001). There were no significant differences in acute rejection ( P = 0.15) or 1-y graft survival (93.3% versus 90.5%, P = 0.23). In adjusted analysis, back-to-base NMP was not associated with increased graft failure risk (hazard ratio 1.46; 95% confidence interval, 0.90-2.38; P = 0.13). Findings were consistent in the sensitivity analysis (n = 1001). Conclusions. In-transit and back-to-base NMP strategies yield comparable clinical outcomes in DCD liver transplantation. Strategy selection may be guided by logistical infrastructure and center-level expertise without compromising recipient outcomes.