Effect of Warm Ischemia Time During Laparoscopic Partial Nephrectomy on Early Postoperative Glomerular Filtration Rate

Purpose: We evaluated the effect of warm ischemia time on early postoperative renal function following laparoscopic partial nephrectomy. Materials and Methods: Of 453 patients who were surgically treated for renal tumors between May 2001 and September 2007, and who were identified in our database 128 underwent laparoscopic partial nephrectomy. Of these 128 patients 101 who were evaluable had complete demographic, operative, preoperative and early postoperative data available. Renal function was estimated using the glomerular filtration rate. Warm ischemia time was stratified into 4 interval groups and also analyzed based on different time cutoffs. Ultimately we also tested the relationship between postoperative renal failure, and preoperative factors and warm ischemia time. Results: Warm ischemia time interval analysis was not significant. However, when analyzing the effect of warm ischemia time cutoffs, patients with warm ischemia time greater than 40 minutes had a significantly greater decrease in the glomerular filtration rate (p = 0.03) and a lower glomerular filtration rate postoperatively. The incidence of renal function impairment was more than 2-fold higher in those with a warm ischemia time of greater than 40 minutes than in the other groups (p = 0.077). Warm ischemia time was significant on univariate analysis when only patients with a preoperative glomerular filtration rate of 60 ml per minute per 1.73 m² or greater were analyzed. However, this did not hold as an independent predictor of postoperative renal function impairment on multivariate analysis. The preoperative glomerular filtration rate was the only independent predictor of postoperative renal function impairment. Conclusions: A warm ischemia time of 40 minutes appears to be an appropriate cutoff, after which a significantly greater decrease in renal function occurs after laparoscopic partial nephrectomy. The preoperative glomerular filtration rate was the only independent predictor of an increased risk of renal insufficiency following laparoscopic partial nephrectomy.