Cortex kidney tissue partial oxygen pressure depends on percentage of active oxygenation during oxygenated hypothermic machine perfusion.

Background: Preclinical and clinical studies have demonstrated the advantages of oxygenated hypothermic machine perfusion (HMPO₂) during kidney preservation. However, the optimal oxygenation levels during HMPO₂ remain undetermined. The aim of this study was to compare different levels of oxygenation (0%, 21%, 50%, and 100%) during 22 h of active oxygenated HMP (HMPO₂) using oxygen preloading by bubbling oxygenation in the preservation solution and continuous surface oxygenation during MP in a porcine DCD model.

Methods: After 60 min of warm ischemia time, both kidneys of an 80 kg pig were procured and randomized to one of the following groups: (1) 22-h static cold storage (n = 6), (2) 22-h HMP without active oxygenation (n = 6), (3) 22-h HMPO₂ 21% O₂ (n = 6), (4) 22-h HMPO₂ 50% O₂ (n = 6), and (5) 22-h HMPO₂ 100% O₂ (n = 6). The primary outcome measure was to compare the different oxygen levels among the different groups assessed by cortex kidney tissue oxygen partial pressures (tpO₂).

Results: Continuous HMPO₂ resulted in a significant modification of cortex kidney tpO₂. In addition, tpO₂ was dependent on the percentage of oxygenation. One hundred percent oxygen resulted in a significantly higher tpO₂ compared to all other study groups. In line with that, ATP resynthesis was significantly higher in the HMPO₂ 100% group.

Conclusions: This study demonstrates that continuous HMPO₂ results in a significant modification of tpO₂ compared with SCS, and the degree of tpO₂ is positively correlated with the percentage of active oxygenation during HMP. Metabolic profile analyses (ATP resynthesis) suggest that the aerobic mechanism is better supported with higher oxygen levels (50% and 100% oxygenation).