Impact Of Warm Ischemia

Hemostasis remains a primarily task during laparoscopic partial nephrectomy. Temporary en bloc renal hilar clamping allows a bloodless field with enhanced visualization during tumor excision and renal repair. Supported by experimental and clinical data, several modalities of hilar control during laparoscopic partial nephrectomy have been advocated, including the clamping of the renal artery alone, both renal artery and vein, and intermittent occlusion (96-98). Advantages and disadvantages of these means are still debated (99,100), yet conclusive data are not available. Critical renal ischemia time has generally been considered to be a 30-minute cutoff (101). In this setting, eventual recovery requires three days. laparoscopic partial nephrectomy may require somewhat longer ischemic times compared to open nephron-sparing surgery (65). Nevertheless, complete recovery of renal function after 60 minutes of warm ischemia has been reported (102,103).

Shekarriz et al. (104) prospectively evaluated the impact of warm ischemia on postoperative renal function in 17 patients undergoing transperitoneal laparoscopic partial nephrectomy with hilar clamping for exophytic tumors. Preoperative and postoperative differential glomerular filtration rate and renal function was evaluated in all patients by technetium-99-labeled diethylenetetraminepenta-acetic acid renal scans performed one month before and three months after laparoscopic partial nephrectomy. Mean operative time was 3.1 hours (range, 1.5-4.8), mean warm ischemia time 22.5 minutes (range, 10-44), mean blood loss 305 cm3 (range, 50-1000), and mean hospital stay 2.15 days (range, 1-3). Postoperative complications included pulmonary edema in one patient, and arterioca-lyceal fistula in one patient. Preoperatively, mean creatinine was 0.89 mg/dL (range, 0.7-2), mean glomerular filtration rate in the target kidney was 75.56 mL/min (range, 39.4-105), and mean differential renal function of the target kidney was 50.2% (range, 43-58%). On postoperative evaluation at three months mean serum creatinine was 0.96 mg/dL (range, 0.7-1.9), mean glomerular filtration rate in the operated kidney was 72.03 mL/min (range, 31-101), and mean differential renal function in operative kidney was 48.07% (range, 39-63%). Hilar clamp time did not significantly correlate with change in renal function, or change in glomerular filtration rate. The authors concluded that temporary hilar clamping during laparoscopic partial nephrectomy with a mean warm ischemia time of 22.5 minutes was safe in patients with functioning contralateral kidney.

We evaluated the impact of renal hilar clamping-induced warm ischemia on renal function in 179 patients undergoing laparoscopic partial nephrectomy for tumor at our center (105). Attention was focused on 15 patients undergoing laparoscopic partial nephrectomy for tumor in a solitary kidney, and on 12 patients with both functioning kidneys who had objectively documented differential renal function (preoperative and one-month postoperative serum creatinine levels and radionuclide renal scans) undergoing unilateral laparoscopic partial nephrectomy. Overall mean warm ischemia time was 31 + 10 minutes (range, 4-55). For further analysis, the entire study population was stratified according to (i) warm ischemia time (warm ischemia <30 minutes; warm ischemia >30 minutes); (ii) warm ischemia and age (>warm ischemia <30 minutes; warm ischemia > 30 minutes; age < 70 years; age (70 years); and (iii) warm ischemia and baseline serum creatinine (>warm ischemia < 30 minutes; warm ischemia > 30 minutes; serum creatinine <1.5 mg/dL; serum creatinine (1.5 mg/dL). In this study, no kidney was lost due to ischemic sequelae. The nadir postoperative serum creatinine in patients with a solitary kidney was commensurate with the approximate amount of renal parenchyma resected. Temporary postoperative hemodialysis was required after 60% laparoscopic heminephrectomy in one patient with a 6.5 cm tumor in a solitary kidney. Comparing preoperative and one-month postoperative renal scans in the 12 patients with both functioning kidneys, calculated reduction of function from baseline in the operated kidney was 29%. Expectedly, unilateral laparoscopic partial nephrectomy in the setting of bilateral functioning kidneys did not show significant impact on serum creatinine. The authors concluded that a warm ischemia time of approximately 30 minutes leads to minimal clinical sequelae.

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