Impact of Monitoring Vancomycin Peak and Trough Concentrations versus Trough Concentrations Alone on Dose Adjustments: An Outcomes Analysis

Abstract

Objective: To determine whether monitoring both steady-state peak and trough serum vancomycin concentrations or steady-state trough serum vancomycin concentrations alone resulted in differences between two groups of patients in terms of dose adjustment, clinical outcome, and toxicity. Design: The study was a retrospective chart review of patients treated with vancomycin during two time periods. Group 1 represented patients hospitalized between July 1, 1996, and January 31, 1997. These patients routinely had vancomycin peak and trough concentrations measured. Group 2 represented patients hospitalized from July 1, 1997, to January 31, 1998, who were monitored with trough vancomycin concentrations only. Setting: A university teaching hospital. Patients: Adults at least 18 years of age who received a constant dose of intravenous vancomycin for at least three consecutive days were eligible for inclusion in the study. Patients were selected from lists generated by the Microbiology Department. The lists contained vancomycin serum concentrations measured during those time frames. Main Outcome Measures: The main outcome measure was to assess whether dose adjustments by prescribers were influenced by both vancomycin peak and trough concentrations or by the trough concentration alone. Results: Forty-nine and 37 patients met the criteria for inclusion into group 1 and group 2, respectively. The mean duration of therapy in group 1 (15 ± 10 d) was not statistically different from that of group 2 (14 ± 12 d). Patients in both groups received a mean daily vancomycin dose of approximately 1,500 mg. In analyzing treatment decisions, trough concentration was the only significant factor influencing a change in total daily dose of vancomycin (p = 0.038). Furthermore, although the method of vancomycin serum concentration monitoring varied between the two groups, the mean clinical outcome parameters were comparable. Conclusions: Prescribers tended to adjust vancomycin regimens based only on trough serum concentrations; monitoring peak serum vancomycin concentrations did not enhance patient care. Mean outcome parameters in the two groups were comparable.