396. Aminoglycoside Acute Kidney Injury (AKI) Following the Implantation of Tobramycin Loaded Polymethylmethacrylate (PMMA) Cement and Calcium Sulfate (CaSO4) Beads for the Treatment of Periprosthetic Joint Infection (PJI)

Abstract

BackgroundAntibiotic loaded bone cement (ALBC) in PMMA, generally with tobramycin and vancomycin (TV) is commonly used for the treatment of PJI. CaSO4 beads, loaded with TV is biodegradable and can be used alone or in combination with PMMA. Identification of AKI following documentation of sustained supra-therapeutic tobramycin levels a patient with chronic PJI treated with ALBC (both PMMA + CaSO4) prompted the development of guidelines to mitigate risk of AKI in patients treated with ALBC. Although AKI may be enhanced with vancomycin, case reports with TV in PMMA implicate tobramycin. We provide data in a cohort of patients treated for PJI using PMMA or PMMA + CaSO4.MethodsData were obtained to describe clinical findings. As part of a quality improvement initiative, tobramycin and serum creatinine levels were obtained in eight subsequent patients who received PMMA or PMMA + CaSO4 and clinical guidelines were developed to standardize aminoglycoside dosing and monitoring. Vancomycin levels were not routinely monitored.ResultsFigure 1 describes the clinical course of the index patient. Table 1 lists doses, serum creatinine and tobramycin levels the cohort of PJI patients. All patients treated with PMMA + CaSO4 had tobramycin levels from 3.5 to 8.7 µg/mL on a postoperative day (POD) 1 compared with < 2 µg/mL in patients treated with PMMA alone. All patients’ levels peaked on POD 1.ConclusionPatients treated with CaSO4 had higher levels in the early postoperative period compared with patients treated with PMMA. In all patients, serum levels appeared similar after 48 to 72 hours. Our experience suggests the use of CaSO4 + PMMA may have important clinical consequences in patients with decreased clearance and/or those at risk for early postoperative renal impairment. Guidelines developed mitigated this potential complication since we have not identified AKI in subsequent patients undergoing treatment of PJI with ALBC. Features of guidelines included: (1) identification of high-risk patients; (2) a flowsheet to guide dosing recommendations based on low/high risk; (3) routine monitoring of levels on POD 1 with a goal of tobramycin < 2 as a surrogate for toxicity. Pharmacy approved dosing must be incorporated into guidelines of care for patients undergoing arthroplasty where ALBC is used. Disclosures All authors: No reported disclosures.