Serum concentration of vancomycin is a diagnostic predictor of nephrotoxic acute kidney injury in septic patients in clinical and surgical wards

Introduction and Aim: There have been few studies to evaluate the monitoring of plasmatic concentrations of vancomycin in septic patients and their association with acute kidney injury (AKI) and death. This study aimed to evaluate the prevalence of adequate, subtherapeutic, and toxic serum concentrations of vancomycin in hospitalized septic patients and to associate the adequacy of therapeutic monitoring with clinical outcomes. Methodology: This was a cohort-unicentric study that evaluated septic patients aged >18 years using vancomycin admitted to clinical and surgical wards of a Brazilian university center from August 2016 to July 2017 in a daily and uninterrupted way. We excluded patients with AKI prior to the introduction of vancomycin or with AKI development <48 hours after use, patients with AKI of other etiologies, stage V chronic kidney disease, and pregnant women. Results: We evaluated 225 patients, and 135 were included. Evaluation of serum concentration of vancomycin was realized in 94.1%, and of those, 59.3% presented toxic concentrations. The prevalence of AKI was 27.4% and happened on average on the ninth day of vancomycin usage. Between the fourth and sixth days, vancomycin serum concentration of >21.5 mg/L was a predictor of AKI, with area under the curve of 0.803 (95% CI 0.62–0.98, p=0.005), preceding the diagnosis of AKI by at least 3 days. Of these patients, 20.7% died, and serum concentrations of vancomycin between the fourth and sixth days were identified as risk factors associated with negative outcomes. Conclusion: Serum concentration of vancomycin is an excellent predictor of AKI in patients admitted to wards, preceding the diagnosis of AKI by at least 72 hours. Toxic concentrations of vancomycin are associated with AKI, and AKI was a risk factor for death. Also, serum concentration of vancomycin >21.5 mg/L was the only variable associated with death in the Cox model.