PO2 21% oxygenated hypothermic machine perfusion in kidney transplantation: Any clinical benefit?

Background: In deceased donor kidney transplantation (KT), the use of hypothermic machine perfusion (HMP) has been acquiring the status of best practice in the pre-transplant management of kidney grafts. Two types of HMP are currently available, oxygenated HMP and non-oxygenated HMP. However, data on the real clinical impact of oxygenation on KT outcome are still heterogeneous. Methods: Retrospective study on a cohort of 103 patients transplanted with a single kidney graft that was managed either with end-ischemic oxygenated (O-2 group, Waves Machine, n = 51, 49.5%) or non-oxygenated HMP (no-O-2 group, Life Port Kidney Transporter Machine, n = 52, 50.5%), during the period January 2016-December 2020. Oxygenation was performed at pO(2) 21%. Results: The median cold ischemia time was 29 h:40 min [IQR 26 h:55 min-31 h:10 min] and the prevalence of grafts from extended criteria donors (ECD) was 46.7%, with a median kidney donor profile index (KDPI) of 72 [41-94]. The study groups were homogeneous in terms of recipient characteristics, ischemia times and donor characteristics. O-2 and no-O-2 groups showed comparable outcomes in terms of delayed graft function (O-2 vs no-O-2, 21.5% vs 25%, p = 0.58), vascular (0.2% vs 0.2%, p > 0.99) and urologic (13.7% vs 11.5%, p = 0.77) complications, and episodes of graft rejection (11.7% vs 7.7%, p = 0.52). At 1 year follow up, even creatinine serum levels were comparable between the groups (1.27 mg/dL [1.09 and 1.67] vs 1.4 mg/dL [1.9-1.78], p = 0.319), with similar post-transplant trend (p = 0.870). No significant benefit was either observed in ECD or KDPI > 60 subgroups, respectively. Conclusions: Oxygenation at pO(2) 21% during HMP seems not to significantly enhance the KT outcomes in terms of postoperative complications or graft function.