Characterization of variables for potential impact on vancomycin pharmacokinetics in thermal or inhalation injury.

OBJECTIVE: To characterize the pharmacokinetics of vancomycin dosing in thermal or inhalation injury as they relate to percent total body surface area burn (TBSA) and days since injury (DSI).

METHODS: This retrospective 3-year study included patients with thermal or inhalation injury receiving vancomycin. Patient demographics and course data were collected using the institution's electronic medical record.

RESULTS: Six hundred and fifty-four patients were included in the study; 124 remained after exclusion. Clearance (CL) was augmented in patients closer to their date of injury. CL and total daily dose requirements significantly increased with larger percent TBSA injured that was independent of volume of distribution (Vd). Larger percent TBSA also predicted increased occurrence of renal injury prior to vancomycin initiation. A modified sample set was also analyzed to control for renal dysfunction. Creatinine clearance (CrCl) estimated via the Cockcroft-Gault equation significantly impacted CL and total daily dose. To obtain a goal trough of 15-20mg/L, the average patient in the modified sample with ≥10% TBSA required 64.7mg/kg/day (or 16.2mg/kg every 6hours).

CONCLUSIONS: DSI, percent TBSA, and CrCl can be used to predict faster vancomycin CL and need for higher total daily doses. Augmented pharmacokinetics can occur as early as two days after injury and decrease with time. Acceptable target trough attainment is still lacking and this data should assist in performance improvements for initial vancomycin dosing.