Impact of Obesity on Acute Kidney Injury Incidence Among Patients Treated with Piperacillin–Tazobactam and Vancomycin

BACKGROUND: Obesity is associated with worse patient outcomes in a variety of clinical scenarios. It is unclear from previous research if obesity is associated with increased acute kidney injury (AKI) among patients receiving concomitant piperacillin-tazobactam (TZP) and vancomycin (VAN). METHODS: Clinical and demographic data were collected from the University of Kentucky Center for Clinical and Translational Science Enterprise Data Trust. Patients who received TZP+VAN for at least 48 hours in combination were included. Patients with CKD, a baseline creatinine clearance (CrCl) < 30 mL/minute, CF, or missing height and weight information were excluded from analysis. AKI was defined using the Risk, Injury, Failure, Loss, End-stage (RIFLE) criteria. A weight cutoff point of 91 kg was determined by finding the most predictive bivariable logistic regression model with weights varying from 70 kg through 120 kg via minimization of the Akaike information criterion. Basic descriptive statistics were performed and bivariable and multivariable logistic regressions were performed. RESULTS: In total, 8125 patients were included in the final analysis. A total of 2452 (30.2%) of patients weighed ≥91 kg. Patients weighing less 91kg were less likely to receive concomitant nephrotoxins and had higher baseline CrCl (97.3 [70.1–128.1] mL/minute vs. 91.8 [68.1–116.5] mL/minute, <0.00001). Baseline severity of illness was similar between groups; however, diabetes (38.9% vs. 20.8%, P < 0.00001), hypertension (63.5% vs. 46.7%, P < 0.00001), and heart failure (14.8% vs. 12.5%, P = 0.007) were more common among the 91kg+ patients. Median daily VAN doses were less in the sub-91kg patients (2000 [1250–2500] mg vs. 3000 [2000–3500] mg, P < 0.00001); however, weight-based doses were lower in the ≥91kg group (25.5 [16.3–31.5] mg/kg/day vs 27.9 [18.7–34.2] mg/kg/day, P < 0.00001). AKI was more common in the patients weighing ≥91kg (23.8% vs. 17.8%, P < 0.00001; adjusted odds ratio 1.46 [95% CI 1.28–1.66]). CONCLUSION: Obesity appears to increase the incidence of AKI among patients treated with TZP+VAN, independent of clinically important confounders, with an important breakpoint occurring at 91 kg. DISCLOSURES: R. Hall, Genentech: Scientific Advisor, Consulting fee Merck: Grant Investigator, Grant recipient