Evaluation of Renal Function Estimation Formulas Specific to Dynamic Renal Function for Drug Dosing in Critically Ill Patients.

Objectives: The study compared estimated creatinine clearance (eCrCl) between the Cockcroft-Gault (CG) equation and the Jelliffe, Chiou, and Brater equations designed for estimation in dynamic renal function and resulting antimicrobial dosing concordance of five antimicrobials (cefepime, meropenem, piperacillin/tazobactam, vancomycin, and fluconazole) commonly used in the intensive care unit (ICU).

Methods: Electronic medical records were used to identify the target patient population. Analysis of variance tests with repeated measures were performed to compare eCrCl. Bowker's tests of symmetry were applied to compare the dosing regimen discordance between CG and candidate equations.

Results: From January 1, 2008 through December 31, 2012, we identified 387 patients with acute kidney injury (AKI), among whom 62% (n = 240) were older adults (65 years and older) and 46% (n = 178) were obese (body mass index ≥30). In the declining phase of renal function, eCrCl means were different between the CG and Brater equations (32.0 vs 26.1 mL/min, < 0.001). The dosing regimen discordance rates (CG vs candidate equations) in declining renal function varied from 19.3% to 25% and were statistically significant for cefepime and meropenem ( < 0.001) based on Food and Drug Administration recommendations for dose adjustment. In the improving phase, eCrCl means were different ( < 0.001) between CG (43.0 mL/min) and candidate formulas (Brater 47.9, Chiou 31.7, and Jelliffe 55.3 mL/min). The dosing regimen discordance rates (CG vs candidate equations) in the improving phase varied from 8.3% to 39% and were statistically significant for all 5 antimicrobials ( < 0.001).

Conclusions: Differences in eCrCl between CG and candidate formulas were observed in surgical ICU patients with acute kidney injury. Discordant dosing recommendations may affect antimicrobial regimens in ICU patients with dynamic renal function.