Direct Measurement of Creatinine Clearance over a Short Interval in Intensive Care Settings

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 (CrCl(direct) = urine creatinine × urine flow rate/serum creatinine) over a short interval (3–6 hours) was explored to identify patients with AKI. MATERIALS AND METHODS: 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 CrCl(direct) 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: CrCl(direct) 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. HOW TO CITE THIS ARTICLE: Law LSC, Lo EAG, Yeoh SF. Direct Measurement of Creatinine Clearance over a Short Interval in Intensive Care Settings. Indian J Crit Care Med 2021;25(7):800–802.