Hypothermia During Partial Nephrectomy for Patients with Renal Tumors: A Randomized Controlled Trial.

PURPOSE: Surgeons induce renal hypothermia during partial nephrectomy to preserve kidney function, without strong evidence of benefit. This trial examined the effectiveness and safety of renal hypothermia during partial nephrectomy. MATERIALS AND METHODS: We conducted a parallel randomized controlled trial of hypothermia versus no hypothermia (control group) during partial nephrectomy at 6 academic hospitals. Eligible patients had a planned open partial nephrectomy for the treatment of a renal tumor. During surgery, after clamping the renal hilum, patients were randomized to the intervention or control arm in a 1:1 ratio using permuted blocks of variable lengths (2 and 4), stratified by institution, using a computer-based program. Surgeons and study coordinators were masked to treatment allocation until the renal hilum was clamped. Overall glomerular filtration rates were determined before, and 1-year after, surgery. The primary outcome was measured glomerular filtration rate (mGFR) assessed by the plasma clearance of 99mTc-DTPA. The trial (NCT01529658) was designed with 90% power to detect a minimal clinically important difference in mGFR of 10 ml/minute/1.73 m2 at a 5% significance level. RESULTS: Of the 184 patients randomized, hypothermia and control patients had similar baseline mean mGFR (87.1 vs 81.0 ml/minute/1.73 m2). One hundred and sixty-one (79 hypothermia, 82 control) were alive with primary outcome data 1 year after surgery. The change in mGFR 1 year after surgery was -6.6 ml/minute/1.73 m2 in the hypothermia group and -7.8 ml/minute/1.73 m2 in the control group (mean difference 1.2 ml/minute/1.73 m2, 95% CI -3.3 to 5.6). Operated-kidney change in mGFR was similar between groups (-5.8 vs -6.3 ml/minute/1.73 m2; mean difference 0.5 ml/minute/1.73 m2, 95% CI -2.9 to 3.8). No clinically significant difference in the mGFR was observed when patients were stratified by pre-planned subgroups. Renal hypothermia did not impact the secondary outcomes of surgical complications and patient reported quality of life. CONCLUSIONS: Renal hypothermia during partial nephrectomy does not preserve kidney function in patients with normal or mildly impaired renal function.