Estimating measured creatinine clearance for critically ill trauma patients with presumed normal kidney function.

Purpose: The intent of this study was to evaluate the predictive performance of two common methods for estimating kidney function in critically ill trauma patients with presumed normal kidney function.

Methods: A retrospective analysis of 2 common methods for estimating kidney function, the Cockcroft-Gault (CG) and Chronic Kidney Disease Epidemiology Collaboration (2021 CKD-EPI) equations, was undertaken for adult trauma patients. Patients with a 24-hour urine collection for determination of measured creatinine clearance (mCrCl) within 4 to 14 days after admission were included in the study. Patients with a serum creatinine concentration of >1.5 mg/dL or who required dialysis were excluded.

Results: The 200 patients included in the study had a median (IQR) mCrCl of 184 (141-233) mL/min; both the CG and CKD-EPI equations were biased towards underpredicting mCrCl, with median (IQR) values of 135 (100-177) mL/min and 135 (113-155) mL/min, respectively (P < 0.001). One hundred twenty-two patients had augmented renal clearance (ARC), defined as an mCrCl of >129 mL/min/1.73m2, and those patients had a median (IQR) mCrCl of 216 (188-265) mL/min; both the CG and CKD-EPI equations were biased towards underpredicting mCrCl in patients with ARC: the median (IQR) estimates were 160 (126-197) mL/min and 147 (129-164) mL/min, respectively (P < 0.001). For those without ARC (n = 78), the median (IQR) mCrCl was 125 (98-153) mL/min; both the CG and CKD-EPI equations underpredicted mCrCl, with median estimates of 98 (76-116) mL/min and 112 (92-132) mL/min, respectively (P < 0.001). The CKD-EPI equation outperformed the CG method for all markers of precision in patients without ARC (P < 0.003).

Conclusion: Common predictive equations for assessing kidney function in critically ill patients with traumatic injuries underpredicted mCrCl, especially in those with ARC.