Warm ischemia less than 30 minutes is not necessarily safe during partial nephrectomy: every minute matters

At the 11th Annual Meeting of the Society of Urologic Oncology (SUO), an expert panel discussed the importance of warm ischemia time on renal function during partial nephrectomy. The position of this manuscript is that every minute of warm ischemia time has a deleterious effect on renal function outcomes following partial nephrectomy.

The presentation was derived from a review of the published urologic, nephrology, and transplant literature related to warm ischemia time and renal function outcomes.

There exist numerous clinical models to study the effects of warm ischemia on renal function. These include the bilateral kidney, unilateral partial nephrectomy, solitary kidney partial nephrectomy, and transplant kidney model. Each of these models provides evidence for minimizing warm ischemia time to prevent acute renal failure, chronic kidney disease, and end stage renal failure. In the best available model, solitary kidney partial nephrectomy, each minute of warm ischemia was found to be associated with a 6% increased risk of acute renal failure, 7% increased risk of acute-onset end stage renal disease (ESRD), and 4% increased risk of new-onset ESRD while controlling for preoperative renal function, tumor size, and surgical approach.

There is ample evidence, consistent across multiple human kidney models, supporting the potentially deleterious renal effects of warm ischemia during partial nephrectomy. There does not appear to be a known safe threshold of warm ischemia since each minute sequentially contributes to the risk of developing acute kidney injury and renal function decline. Ultimate renal function following PN is dependent on the "3 Qs": quality (renal function prior to surgery), quantity (renal parenchyma preserved during surgery), and quickness (ischemia time).