Messengers of Renal Graft Quality During Warm and Cold Ischemia: A Porcine Microdialysis Study

Abstract

IntroductionLittle is known about local graft metabolism during warm and cold ischemia before renal transplantation. We sought to characterize local metabolic changes in renal grafts during storage to understand acceptable ischemia time. MethodsKidneys from 60- or 15-kg pigs were randomized to cold (4°C) or warm (37°C) storage. Local renal graft metabolism was monitored for 24 hours by use of microdialysis and measurements of glycerol, glutamate glucose and lactate. ResultsFor all metabolites, there was a significant interaction between time, storage temperature, and kidney size (all P < .0001). For local glycerol and glutamate, a significant increase was observed initially during warm storage, reaching a high steady state level. Glycerol remained low in cold kidneys for 80 minutes, but after 100 minutes there was an ongoing increase (P = .003) with no steady-state maximum level reached during the first 24 hours. The curves in the 2 size groups were parallel (P = .384) with 74% higher glycerol content in large kidneys (P = .005). Glutamate increased in cold kidneys in a similar manner in the 2 size groups (P = .924). Warm storage caused a rapid glucose decline within 60–100 minutes. In cold storage, glucose remained at a steady level until 480 minutes. ConclusionsReducing cold ischemia time is of great importance, because concentrations of ischemic metabolites continuously increase in renal grafts. Furthermore, small kidney grafts from growing individuals are more resistant to cold ischemia but more susceptible to warm ischemia. In the setting of donation after circulatory death with prolonged warm ischemia, ongoing catabolism in the potential renal graft may be measured by microdialysis to achieve optimal timing of transplantation.