LAUSR

Introduction/Hypothesis: The efficacy of vancomycin has historically been associated with a defined trough concentration range. Accumulating evidence indicates vancomycin efficacy is more strongly associated with the achievement of a 24 hour area under the curve/minimum inhibitory concentration (AUC24/ MIC) of 400-600. The calculation of AUC24/MIC ratio may be clinically cumbersome. This pilot study was conducted to determine if a steady state vancomycin trough concentration range would correlate with AUC24/MIC ratio of 400-600. Methods: One hundred-four surgical critically ill patients were included in this observational study receiving vancomyin for the treatment of gram positive infections. Utilizing population pharmacokinetic volume of distribution, vancomycin dose and steady state vancomycin trough concentrations, each patient’s vancomycin elimination rate constant and clearance were calculated and subsequently used to calculate each patient’s AUC24. Assuming an MIC of 1 mg/L, the AUC24/MIC ratio was calculated using the formula AUC24/MIC = Dose24 / Cl x MIC. Descriptive analysis and Chi-square were used to assess the association of a steady state vancomycin trough concentration range and an AUC24/MIC ratio of 400-600. Results: Ninety-one patients were evaluated: 13 patients were excluded because vancomycin serum concentrations were not taken appropriately, and/or patients were not at steady state. The results demonstrated a statistically significant relationship between a vancomycin serum trough concentration range and AUC24/MIC ratio (p<0.01). 87% of patients with a vancomycin serum trough concentration range of 10-18.7 mg/L also achieved an AUC24/MIC of 400-600. Conclusions: The results of this pilot study provides initial information to perform a prospective clinical study with a larger patient population and known MIC data to determine if a vancomycin trough concentration of 10-18 mg/L will provide an AUC24/MIC ratio of 400-600. This would allow a clinician to be confident that the patient is being treated effectively and safely with routine drug monitoring.