Direct measurement of creatinine clearance over a short interval in intensive care settings

Abstract

Background: The definition of acute kidney injury (AKI), based on serum creatinine and urine output, bears significant limitations in intensive care units (ICUs). Serum creatinine has significant lag-time as it needs to be accumulated and stabilized at a new level whereas urine output is affected by diuresis, antidiuresis, and antinatriuresis. Direct measurement of creatinine clearance (CrCldirect = urine creatinine × urine flow rate/ serum creatinine) over a short interval (3–6 hours) was explored to identify patients with AKI. Method: We reanalyzed a previous published dataset. We included 11 patients who had serial daily urine collections over 0 to 3 days of stay in ICU and baseline (day-1) serum creatinine levels. Result: The ratio of CrCldirect on day 0 to baseline creatinine clearance predicted the progression of AKI over the subsequent 1 to 3 days of ICU stay [area under receiver operating characteristic curve = 0.933 and 95% confidence interval (CI) = 0.780–1.000]. Discussion: CrCldirect over a short interval may be an alternative marker of kidney function. Future studies may explore its use to identify patients with AKI who may benefit from early renal replacement therapy.