SAN DIEGO, CA—A one-time dose of gentamicin, or vancomycin plus gentamicin, for surgical prophylaxis in older patients undergoing radical cystectomy is a safe option, with no increased risk of postoperative acute kidney injury, investigators reported at IDWeek 2015.

Zhe Han, PharmD, from Pharmacy Services at the University of Chicago Medicine in Chicago, Illinois, and colleagues explained that at their institution, patients undergoing radical cystectomy previously received cefoxitin or a fluoroquinolone. However, due to increasing fluoroquinolone resistance and postoperative infections in patients undergoing radical cystectomy, they instituted gentamicin 4mg/kg for surgical prophylaxis to offer broader spectrum coverage against fluoroquinolone-resistant Enterobacteriaceae.

Due to a concern about the association between nephrotoxicity and aminoglycosides, they compared incidence of postoperative acute kidney injury between patients who received gentamicin vs. historical controls. Included was a random sample of adult patients who underwent radical cystectomy between March 1, 2012 to May 22, 2013, and May 23, 2013 to May 30, 2014; excluded were those with end-stage renal disease.

Renal function was evaluated for 5 days postoperatively and acute kidney injury defined per Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease (RIFLE) criteria. Risk factors were assessed using regression analysis.

Among the 165 patients included, 60 had received gentamicin at a mean dose of 4.3 ± 1.1mg/kg. The majority received a one-time dose; 2 patients had received 2 doses and 4 patients, 3 doses. Demographics and operating room time were similar between the 2 groups.

“Incidence of postoperative acute kidney injury did not change with the addition of gentamicin (61% vs. 53%, P=0.26),” the investigators reported. Using RIFLE criteria, risk was 24% vs. 26% (P=0.26), injury 28% vs. 20% (P=0.43), and failure 9% vs. 6% (P=0.63).

The odds ratio for univariate analysis of risk factors and their association with postoperative acute kidney injury were diabetes mellitus, 2.6 (P=0.03); chronic kidney disease, 1.9 (P=0.22); body mass index (BMI) ≥30, 2.1 (P=0.03); other nephrotoxic medications, 1.7 (P=0.10); postoperative hypotension, 1.2 (P=0.61); age ≥65 years, 2.1 (P=0.03); gentamicin use , 0.7 (P=0.28); vancomycin plus gentamicin use, 2.0 (P=0.24); and operating room time, 1.0 (P=0.05).

Diabetes mellitus, BMI ≥30, age ≥65 years, and operating room time met a priori P<0.2 for inclusion in multivariate analysis; among these, BMI ≥30 (OR 2.2, 95% CI: 1.0–4.6; P=0.04) and age ≥65 years were the only significant risk factors (OR 2.6, 95% CI 1.2–5.5]; P=0.02), they concluded.