Defining maximal renal tolerance to warm ischemia in porcine laparoscopic and open surgery model

Objectives. To establish the upper limit for warm ischemia time (WIT) beyond which irreversible renal failure will occur in a single-kidney porcine model. The maximal renal tolerance during WIT is currently under revision. Traditionally, 30 minutes was defined as the safe limit for renal WIT. However, accumulating data have suggested that a WIT of up to 90 minutes may not result in permanent damage. Methods. Twenty female pigs weighing 60 to 80 lb at arrival underwent initial right laparoscopic nephrectomy to create a single-kidney model. Twelve days later, the animals were randomized into four groups of 5 animals each: 120 minutes of open WIT, 120 minutes of laparoscopic WIT, 5 open controls, and 5 laparoscopic controls. Renal function was assessed with serial glomerular filtration rate and serum creatinine measurements, which were assessed preoperatively and on postoperative days (PODs) 1, 3, 8, and 15. Results. No significant difference existed between the laparoscopic and open groups. The glomerular filtration rate reached the lowest value and the serum creatinine levels peaked on POD 3 and were significantly different from baseline at PODS 1, 3, 8, and 15. Renal function did not return to baseline by POD 15, and 66% of the animals showed significant renal insufficiency (more than 25% decline in glomerular filtration rate) in the study group. Conclusions. After 120 minutes of WIT, no difference in renal function recovery was observed between the laparoscopic and open techniques. A WIT of 120 minutes produced significant renal failure and mortality. Thus, 120 minutes of WIT in the single kidney porcine model exceeds the kidney's tolerance to ischemia.