Vancomycin is the second most highly utilized antibiotic at UCLA Health. The intention of this investigation was to evaluate the impact of vancomycin therapeutic drug monitoring (TDM) on patient care, including frequency of dosing changes made based on appropriate and inappropriately drawn trough concentrations as well as rate of nephrotoxicity.
This was a retrospective chart review of inpatients during September 2014. Eligible subjects were those who received vancomycin and had TDM with a trough concentration >20 mcg/ml. Appropriate timing of trough concentrations was assessed in relation to vancomycin doses in subjects not dependent on renal replacement therapy (RRT). We recorded whether dosing decisions were made based upon these serum concentrations. Rate of acute kidney injury (AKI), defined according to the risk–injury–failure–loss–end-stage renal disease (RIFLE) classification scheme, was collected in subjects not on RRT at baseline. Confirmed MRSA infection per clinical and microbiological data was documented.
390 individuals received vancomycin and had TDM, resulting in 714 vancomycin serum concentrations. We included 94 subjects with a trough concentration > 20 mcg/ml. Of these, 15 were dependent on RRT at baseline. The median duration of vancomycin therapy was 4 days. Per course of vancomycin therapy, a median of 4 vancomycin serum concentrations were drawn. For those on RRT, a median of 7 concentrations were drawn. 25% of subjects (20/79 not on RRT) had troughs drawn inappropriately. Vancomycin dosing changes were made in 11/20 (55%) of these cases. AKI occurred in 28/79 subjects (35%). The majority was categorized as risk or injury; however 5 subjects (6%) met criteria for failure. MRSA infection was confirmed by culture in 5/94 subjects (5%).
Frequent serum TDM of vancomycin requires high resource-utilization from nursing, phlebotomy, pharmacy, and physicians. Given low rates of confirmed MRSA infection and low rates of renal failure, 5% and 6% in this investigation, the significant time spent monitoring serum drug concentrations may be unwarranted and associated with increased patient-care costs.
J. Dang, None
J. Curello, None
M. Kanatani, None
B. Bryant, None
D. Z. Uslan, None