Identification of Risk Factors for Initial Elevated Vancomycin Trough Concentrations

Abstract

Background: Recent literature suggests that elevated vancomycin trough concentrations (>20 µg/mL) may be associated with an increased risk of nephrotoxicity and lead to an increase in mortality and hospital length of stay. Objective: The purpose of this study was to identify variables that may be predictive of elevated initial vancomycin trough concentrations. Methods: Retrospective case–control study of all adult patients who had an initial vancomycin trough concentration measured between January 1, 2013, and December 31, 2014. Case patients had an initial trough concentration >20 µg/mL, while control patients had an initial trough concentration of ≤20 µg/mL. Patients were excluded from the study if they were in the intensive care unit, had unstable renal function, or if they had cystic fibrosis, solid organ transplant, or bone marrow transplant. Results: Of the 512 vancomycin trough concentrations reviewed, 54 patients met the case definition, while 140 patients were randomly selected as controls. In a multivariate model, baseline serum creatinine, body mass index, heart failure, and malignancy were all independently predictive of an initial vancomycin concentration >20 µg/mL. Conclusions: Reduced baseline renal function coupled with increasing body mass index is associated with an increased risk of an elevated initial vancomycin trough concentration. This risk is further enhanced by the presence of heart failure and/or malignancy. When these risk factors are present, it may be prudent to consider implementation of individualized dosing to achieve initial target concentrations.