*Purpose: Normothermic machine perfusion (NMP) is a promising strategy for pre-transplant reconditioning and viability assessment of marginal renal grafts. All current clinical kidney NMP protocols utilize packed red blood cells (pRBC) as an oxygen carrier in the perfusate. This introduces logistical hurdles and potential immunologic risk for the recipient. This feasibility study evaluates whether an oxygenated, cell-free perfusate is sufficient to sustain the ex-vivo function and viability of human kidney grafts, compared to a pRBC-based perfusate.

*Methods: 12 human kidneys, declined for transplantation, were perfused for 6 hours at 37°C. Kidneys were perfused with a pRBC-based perfusate (RBC-group, n=3), or a Williams E-based perfusate (WE-group, n=9). The perfusate was oxygenated with a gas mixture of 95% O₂/5% CO₂.

*Results: The WE-group vascular resistance declined steadily throughout perfusion whereas the RBC-group demonstrated an initial spike in resistance, then declined. The resistance was not significantly different over the course of perfusion (Table 1).

Renal artery flow was higher in the WE-group throughout perfusion (p=0.0002). O₂ delivery was higher in the RBC-group (p=<0.0001) and the O₂ extraction ratio was higher in WE-group (p=0.0014), however, O₂ consumption was similar between groups (p=0.1661), indicating that sufficient dissolved O₂ is present in the perfusate to support aerobic metabolism (Figure 1).

ATP content (p=0.1304) and energy charge (p=0.8785) were similar between groups, indicating a similar overall energy state during perfusion (Figure 2).

*Conclusions: Oxygenated NMP without a heme-based oxygen carrier is feasible for up to 6 hours, resulting in stable hemodynamics, adequate oxygen delivery to support aerobic metabolism, and similar ATP restoration compared to standard pRBC-based protocols.

« Back to 2019 American Transplant Congress