18.18 Modifiable Risk Factors and Clinical Outcomes Associated with Augmented Renal Clearance in Trauma

M. B. Mulder¹, M. S. Sussman¹, S. A. Eidelson¹, C. A. Karcutskie¹, M. A. Cohen¹, A. T. Vidalin¹, G. A. Lama¹, R. S. Iyengar¹, P. M. Elias¹, C. I. Schulman¹, N. Namias¹, K. G. Proctor^{1  1}University Of Miami,Dewitt Daughtry Department Of Surgery: Division Of Trauma And Critical Care,Miami, FL, USA

Introduction:  

Augmented renal clearance ((ARC) defined as creatinine clearance (CL_Cr) > 130 mL/min) has a reported incidence from 14 to 80% in critically ill patients and is associated with therapy failures for renally-cleared drugs. While the awareness of ARC has increased, the clinical implications of this phenomenon are less defined. The objective of this study was to identify modifiable risk factors and clinical outcomes associated with ARC in severely injured trauma patients. 

Methods:  

In 199 trauma ICU patients with a Greenfield Risk Assessment Profile ≥  8, 24-hour CL_Cr was correlated with demographics, interventions (IV fluids, pressors, mechanical ventilation), clinical estimates of GFR (by Cockroft-Gault (CG), modification of diet in renal disease (MDRD), or chronic kidney disease epidemiology (CKD-EPI)), and clinical outcomes (infection, VTE, length of stay (LOS), and mortality). Patients with previous nephrectomy or renal transplant were excluded (n=6).  Univariate and multivariate analysis identified risk factors with significance defined at p≤0.05. Values are M±SD if parametric and median [interquartile range] if not. 

Results:

The population was 46±20 years, 68% male, BMI 28±6 kg/m², 72% blunt mechanism of injury, and injury severity score (ISS) of 24±10. Admission S_Cr was 0.95 [0.78-1.2] mg/dL, CL_Cr was 152±74 ml/min, VTE incidence was 14%, ARC incidence was 57%, and mortality 11%. Clinical estimates of GFR by CG, MDRD, and CKD-EPI underestimated CL_Cr by 14%, 19%, and 18% respectively (all p≤0.001). CL_Cr was lower in patients receiving transfusions (123±74 v 167±67 ml/min, p≤0.001), pressors (117±71 v 162±73 ml/min, p≤0.001), with positive cultures (138±73 v 161±73 ml/min, p=0.041), and in those who expired (92±58 v 159±73 ml/min, p≤0.001).  Univariate analysis of over 15 risk factors and clinical outcomes were analyzed for ARC; values that were significant (p≤0.05) are shown in Table 1. On multivariate logistic regression male gender (OR 4.5 [1.8-11]), S_Cr (OR 0.17 [0.041-0.71]), age (OR 0.96 [0.94-0.99]) and transfusions (OR 0.24 [0.011-0.54) were independent predictors of ARC (all p≤0.01).  

Conclusion:
ARC occurs in half of all high-risk trauma ICU patients and is underestimated by standard clinical equations. ARC is associated with younger males, less transfusions, fewer infections, and reduced mortality. These clinical outcomes are counterintuitive.  Further investigations are warranted to delineate the implications and causality of ARC.