The Efficacy of 22 °C Static Subnormothermic Preservation with an Extracellular-Type Solution for 2 h Warm-Ischemic Porcine Kidneys

<b>Background</b>: Static cold storage is the standard method of kidney preservation following donation after circulatory death (DCD). A previous study on rodent models demonstrated the efficacy of storing DCD kidneys at 22 °C in an extracellular-type solution (ETK). We evaluated the efficacy of storing warm-ischemic kidneys at 22 °C in MHC-inbred miniature swine. <b>Methods</b>: After 2 h warm ischemia, the kidneys were preserved in ETK for one hour at either 4 °C or 22 °C and then subjected to ex vivo normothermic machine perfusion (NMP) for 2 h (<i>n</i> = 3 in each group). The same warm-ischemic kidneys, preserved in ETK (<i>n</i> = 3 in each group) or intracellular-type solution (UW; <i>n</i> = 2 in each group) at either 4 °C or 22 °C, were transplanted into MHC-matched recipients. <b>Results</b>: Compared with kidneys preserved at 4 °C, those preserved at 22 °C showed significantly better physiological and metabolic indices during ex vivo NMP. Furthermore, renal function was significantly higher in transplanted kidneys, and graft biopsies on postoperative day 4 showed more localized necrosis in the renal tubules when kidneys were stored at 22 °C. In contrast, recipient animals with kidneys stored in UW solution did not survive for more than 7 days. <b>Conclusions</b>: Two-hour warm-ischemic kidneys from miniature swine showed improved preservation at 22 °C than at 4 °C when an extracellular-type solution was used.