Potential Association of Weight-Based Gentamicin with Increased Acute Kidney Injury in Urologic Prosthetic Surgery.

BACKGROUND: Despite the known nephrotoxicity of gentamicin, in 2008 the American Urological Association recommended a weight-based gentamicin dose of 5 mg/kg for antimicrobial prophylaxis during urologic prosthetic surgery.

AIM: To identify and characterize rates of acute kidney injury (AKI) in urologic prosthetic surgery, both before and after the implementation of weight-based gentamicin dosing.

METHODS: We performed a single-institution retrospective study of patients receiving perioperative gentamicin during implant, revision, salvage, or explant of inflatable penile prostheses, malleable penile prostheses, or artificial urinary sphincters between the years 2000 and 2017. Patients were stratified into 2 groups, based on administration of either weight-based gentamicin (5 mg/kg or 2-3 mg/kg in cases of poor renal function) or standard-dose gentamicin (80 mg). Patient characteristics and perioperative outcomes were identified. Patients with available preoperative and postoperative (≤7 days) serum creatinine values were included. AKI was defined by Kidney Disease: Improving Global Outcomes criteria. Comparative analyses were performed between groups.

MAIN OUTCOME MEASURE: Our primary outcome was incidence of AKI, with secondary outcomes including device infection rate and length of stay.

RESULTS: Of the 415 urologic prosthetic surgeries performed during the study period, 124 met inclusion criteria with paired preoperative and postoperative serum creatinine values. 57 received weight-based gentamicin (median dose 5.06 mg/kg, interquartile range [IQR] 3.96-5.94) and 67 received standard-dose gentamicin (median dose 1.07 mg/kg, IQR 1.04-1.06), P < .001. There were no significant differences in preoperative renal function or comorbidities between groups; however, the weight-based group was older (median age 64.0 years, IQR 60.0-68.5) compared with the standard-dose group (median age 61.0 years, IQR 55.0-66.0), P = .01, and comprised fewer explant cases (1.8%, 1 of 57) than the standard-dose group (13.4%, 9 of 67), P = .02. The AKI rate was significantly higher in the weight-based group (15.8%, 9 of 57) compared with the standard-dose group (3.0%, 2 o67), P = .02. Device infection rate was similar between groups (5.3%, 3/56 vs 5.2%, 3 of 58), P = 1.00.

CLINICAL IMPLICATIONS: Our data suggest weight-based perioperative gentamicin prophylaxis may be associated with an increased AKI risk, without noticeably improving infection rates.

STRENGTH & LIMITATIONS: Strengths of our study include the Veterans Affairs population analyzed, as well as rigorous inclusion criteria that allowed for a sensitive assessment of postoperative renal function. Limitations include the retrospective design and small sample size.

CONCLUSION: Weight-based gentamicin dosing may warrant closer perioperative monitoring of renal function, and merits larger investigations to further elucidate risks and benefits. Moore RH, Anele UA, Krzastek SC. Potential Association of Weight-Based Gentamicin with Increased Acute Kidney Injury in Urologic Prosthetic Surgery. J Sex Med 2018;XX:XXX-XXX.