Intra-renal resistance reflects warm ischaemic damage, and is further increased by static cold storage: a model of non-heart-beating donor kidneys.

BACKGROUND Non-heart beating donor kidneys increase transplant activity, but their use is associated with a higher rate of both primary non-function and delayed graft function than cadaveric kidneys, due to a period of cold ischaemic damage superimposed on a period of warm ischaemia. We aimed to measure intra-renal resistance in machine perfused porcine kidneys subjected to different periods of warm ischaemic injury, with additional, varying, cold ischaemic times, in an attempt to mimic the injury suffered by NHBD kidneys and test the predictive power of viability testing. MATERIAL/METHODS Landrace pigs were killed by lethal injection, and the kidneys were subjected to varying WITs of 10-90 minutes prior to explantation. Kidneys were subsequently stored for varying cold times of 2 to 48 hours. IRR (pressure/flow) was calculated during 6 hours cold pulsatile machine perfusion. RESULTS For all WITs, IRR was higher at the start than at the end of machine perfusion (P<0.001). There was a strong correlation between IRR on MP, and WIT, but no correlation after 6 hours MP. Intra-renal resistance increased as kidneys were exposed to longer CITs; this effect was most marked for the longer WITs (P<0.004), However, the slope gradient was similar for the different WITs. CONCLUSIONS Early IRR accurately reflects kidney in-situ WIT, and machine perfusion reduces IRR whilst cold ischaemia imposed on periods of warm ischaemia increases IRR and attenuates the beneficial effect of MP. Machine perfusion may partially ameliorate the effects of WIT in terms of IRR, and may prove useful in pre-transplant viability assessment of NHBD kidneys.