Risk Factors and Clinical Outcomes Associated With Augmented Renal Clearance in Trauma Patients

Augmented renal clearance (ARC; i.e., creatinine clearance [CL_Cr] ≥ 130 mL/min) has an incidence of 14%-80% in critically ill patients and has been associated with therapy failures for renally cleared drugs. However, the clinical implications of ARC are poorly defined. We hypothesize that modifiable risk factors that contribute to ARC can be identified in severely injured trauma patients and that these risk factors influence clinical outcome.

In 207 trauma intensive care unit patients, 24-h CL_Cr was correlated with clinical estimates of glomerular filtration rate (by Cockroft-Gault, modification of diet in renal disease, or chronic kidney disease epidemiology), and clinical outcomes (infection, venous thromboembolism [VTE], length of stay, and mortality).

The population was 45 ± 20 y, 68% male, 77% blunt injury with injury severity score of 24 (17-30). Admission serum creatinine was 1.02 ± 0.35 mg/dL, CL_Cr was 154 ± 77 mL/min, VTE incidence was 15%, ARC incidence was 57%, and mortality was 11%. Clinical estimates of glomerular filtration rate by Cockroft-Gault, modification of diet in renal disease, chronic kidney disease epidemiology underestimated actual CL_Cr by 20%, 22%, or 15% (all P < 0.01). CL_Cr was higher in males and those who survived, and lower in those with hypertension, diabetes, positive cultures, receiving transfusions, or pressors (all P < 0.05). On multivariate analysis, male gender (odds ratio [OR] 2.9 [1.4-6.1]), age (OR 0.97 [0.95-0.99]), and packed red blood cells transfusion (OR 0.31 [0.15-0.66]) were the only independent predictors of ARC.

ARC occurs in more than half of all high-risk trauma intensive care unit patients and is underestimated by standard clinical equations. ARC was not associated with increased incidence of VTE or infection but rather is associated with younger healthier males and reduced mortality. ARC seems to be a beneficial compensatory response to trauma.