Impact of total body weight on rate of acute kidney injury in patients treated with piperacillin-tazobactam and vancomycin

Purpose: Results of a study to determine whether obesity is associated with acute kidney injury (AKI) among patients receiving combination therapy with piperacillin-tazobactam and vancomycin are reported. Methods: A retrospective, single-center cohort study of patients who received combination therapy for at least 48 hours was conducted using data from the University of Kentucky Center for Clinical and Translational Science's Enterprise Data Trust. Patients with chronic kidney disease, baseline creatinine clearance of less than 30 mL/min, cystic fibrosis, or missing height or weight information were excluded. Results: A total of 8,125 patients were included in the cohort. Among the variables evaluated, total body weight of 91 kg or more was the variable most predictive of AKI. Patients with a weight of 91 kg or higher were more likely than lower-weight patients to have diabetes (39% versus 21%, p < 0.00001), hypertension (64% versus 47%, p < 0.00001), and heart failure (15% versus 13%, p = 0.007). The median daily vancomcyin dose was lower in patients with a weight of less than 91 kg (2,000 mg versus 3,000 mg, p < 0.00001); however, weight-based doses were lower in patients weighing 91 kg or more (25.5 mg/kg/day versus 27.9 mg/kg/day, p < 0.00001). AKI was more common in patients weighing 91 kg or more (24% versus 18%, p < 0.00001; adjusted odds ratio, 1.46 [95% confidence interval, 1.28-1.66]). Conclusion: Increased total body weight increased the rate of AKI among patients concurrently treated with piperacillin-tazobactam and vancomycin independent of clinically important confounders, with an important breakpoint occurring at 91 kg.