Intraoperative Mannitol Not Essential During Partial Nephrectomy

Intraoperative mannitol is routinely administered for renoprotection in partial nephrectomy (PN). However, there is a paucity of evidence supporting mannitol's renoprotective effect. We performed a retrospective study of mannitol's efficacy in PN.

Using an institutional database, patients undergoing PN from 2006 to 2016 were retrospectively identified and divided into two groups based on mannitol use. Cases with missing serum creatinine measurements were excluded. Mannitol use was dependent on surgeon preference. An independent-samples t-test was used to compare 6-month postoperative estimated glomerular filtration rate (eGFR) between mannitol groups and to compare 6-month eGFR between mannitol dose for patients who received mannitol. Multivariate linear regression was used to estimate 6-month eGFR when adjusting for multiple covariates that were considered clinically relevant to postoperative renal function.

Of the patients, 476 patients were eligible for analysis and 286 received mannitol. Preoperative eGFR (7.8 ± 21.4 mL/minute/1.73 m² vs 75.3 ± 23.1 mL/minute/1.73 m², p = 0.223) and tumor size (3.5 ± 1.7 cm vs 3.4 ± 1.5 cm, p = 0.532) were matched between the mannitol (M+) and no mannitol (M-) groups, whereas warm ischemic time (22.5 ± 11.2 minutes vs 15.0 ± 10.2 minutes, p < 0.001) was longer in the M+ group. There was no significant difference in 6-month eGFR between mannitol groups (70.6 ± 22.2 mL/minute/1.73 m² vs 68.0 ± 23.9 mL/minute/1.73 m², p = 0.225). No significant association between mannitol dose and 6-month eGFR was found. Covariates that significantly predicted 6-month eGFR in our multivariate model were age (β = 0.052, p = 0.042) and preoperative eGFR (β = 0.843, p < 0.001). In addition, neither the use of renal cooling nor the surgical approach (open vs minimally invasive) was significantly associated with 6-month eGFR.

Mannitol did not demonstrate renoprotective effects based on analysis of 6-month postoperative eGFR. In addition, neither the surgical approach nor the use of renal cooling significantly predicted postoperative renal function.