Background: Extended cold ischemia time is associated with higher incidences of delayed graft function and graft failure. Kidneys on hypothermic machine perfusion perform better than comparable kidneys in static cold storage (SCS). This study aimed to determine whether hypothermic perfusion was associated with lowering the deleterious effects of extended cold ischemia time. Methods: Data from the United Network of Organ Sharing database was examined to identify adult first-time, kidney-only recipients from 2005-2022. Multivariable models for death-censored graft failure, uncensored graft failure, delayed graft function, and patient mortality were constructed, and adjusted for donor, recipient, and transplant factors. Kidneys with ≤12 hours SCS, an accepted standard for optimal transplantation, served as the reference group for each model. Results: Among 120,438 allografts, 63% were in SCS and 37% were preserved with hypothermic perfusion. Death-censored graft failure was higher in a dose-dependent fashion as cold ischemia time increased. Kidneys on hypothermic machine perfusion for ≤24 hours had less death-censored graft failure than reference (≤12 hours in SCS) kidneys. Perfusion for 24-36 hours did not differ from reference. After 36 hours, all kidneys had higher death-censored graft failure, regardless of the storage method. Hypothermic machine perfusion lowered the incidence of delayed graft function at every level of cold ischemia time. Conclusions: Hypothermic machine perfusion is an effective strategy for lowering the negative impact of prolonged cold ischemia time, providing transplant teams with greater flexibility to optimize donor and recipient logistics, without compromising long-term graft outcomes.
Pérez-Gutiérrez et al. (2025) studied this question.