A retrospective study to evaluate the impact of two vancomycin dosing frequencies on the incidence of acute kidney injury in a community hospital: a feasibility study

Background: Currently at WellStar North Fulton Hospital, the empiric vancomycin intravenous dosing interval is every 12 hours (Q12H) or more. However, several nomograms include vancomycin dosed at shorter intervals of every 8 hours (Q8H) in certain patient population. The objective of this study is to evaluate the impact of two vancomycin dosing frequencies (Q8H vs Q12H) on the incidence of acute kidney injury (AKI). Methods: A retrospective chart review was conducted for patients who empirically received vancomycin at a dosing interval of Q8H from 2015 to 2016. These patients were well matched with patients who received Q12H vancomycin dosing interval during 2018. Patients 18 years old with a suspected or proven gram-positive infection who received vancomycin and had at least 1 trough drawn at steady state were included. Patients were excluded if they were pregnant, had renal insufficiency, or if trough levels were not drawn appropriately. The eligible patients were divided into two groups according to the vancomycin dosing intervals (Q8H vs Q12H), then evaluated for nephrotoxicity. The primary endpoint of this study was the rate of AKI as defined by Kidney Disease Improving Global Outcomes criteria. Results: Two hundred patients were evaluated, and 130 patients were excluded due to lack of recorded steady state trough levels or due to inappropriately drawn trough levels. Seventy patients were included in the study with 35 patients in each group. Patients (mean age 52.8) were primarily male (60%) and Caucasian (70%), received concomitant nephrotoxic agents (60%). Most common vancomycin indication among both groups was skin and soft tissue infection. AKI was observed in 2 patients (5.7%) in the Q8H group versus 1 patient (2.9%) in the Q12H group. All of these patients who developed AKI were also on concurrent nephrotoxic agents, such as intravenous contrast dye and piperacillin/tazobactam. Conclusions: Patients who received vancomycin treatment Q8H had higher rate of AKI compared to patients in the Q12H group in our hospital during study period. However due to the small sample size of this feasibility study, a large scale study is needed to determine the optimal vancomycin dosing interval