Hypothermic Perfusion in Kidney Allografts with Extended Cold Ischemia Time

Background: Hypothermic perfusion reduces reperfusion injury of kidney allografts. We investigated whether use of hypothermic perfusion offsets effects of extended cold ischemia time (CIT). This is important, as changes in the allocation system have increased CIT for recipient candidates located more than 250 nautical miles from the donor hospital. Methods: UNOS Star Files were used to analyze first-time, single kidney-only allografts from deceased donors from 2005-2022, in order to compare organs preserved only with ice to organs with hypothermic perfusion; those with transient perfusion were excluded. A multivariable Cox model for death-censored graft failure (dcGF) was adjusted for recipient, donor, and transplant characteristics. CIT was categorized as ≤12 hours, 12-24 hours, 24-36 hours, and >36 hours. Kidneys on ice with ≤12 hours CIT served as a reference group, as these are normally considered acceptable for transplantation. Results: Among 120,438 allografts, 62.7% were on ice and 37.3% were pumped. DcGF increased in a dose-dependent fashion as CIT increased, regardless of preservation method. Perfused kidneys with ≤36 hours CIT did not differ from the reference group (Figure). After 36 hours, dcGF was about 25% higher than the reference category, whether perfused kidneys or kidneys on ice. However, in the ≤12 hour, 12-24 hour, and 24-36 hour time categories, pump perfusion was associated with a 13% decrease in the hazard of dcGF (P<0.001 for all). Conclusion: When CIT ≤36 hours, hypothermic perfusion of allografts was associated with signifcantly less dcGF compared to kidneys preserved on ice with similar CIT, with results comparable to kidneys on ice for ≤12 hours. The additional organ longevity may improve organ utilization and promote recipient safety by permitting complex recipients to have their transplant surgeries performed during daylight hours when optimal resources are available.