Evaluation of Catabolic Response in Neurologically Injured Patients With Augmented Renal Clearance

Introduction: Augmented Renal Clearance (ARC) (defined as a creatinine clearance > 130 ml/min) is present in many critically ill patients. The incidence ranges depending on the population but is especially prevalent in patients with neurologic injury, such as traumatic brain injuries or subarachnoid hemorrhages (50-100% of patients). The gold standard for identification of ARC is an 8-hour creatinine clearance measurement. Patients with critical illness also often exhibit hyper-catabolism as a result of the inflammatory response due to their critical illness. This results in an increased caloric need, increased muscle wasting, and immune dysfunction. The gold standard for evaluating metabolic needs for critically ill patients at the bedside is a metabolic cart study (indirect calorimetry). This calculates a measured energy expenditure (MEE) based on oxygen consumption and expiration of carbon dioxide. This study aims to begin to explain potential etiologies for ARC and identify biomarkers which may aid clinicians in identifying the presence and extent of ARC.


Methods: Adults ages 18-65 years old who are within 7 days of admission to an intensive care unit with a primary diagnosis related to a neurological critical illness were screened for inclusion. After obtaining informed consent, the subject underwent an 8-hour urine collection for measured creatinine clearance (mClCr) and urine urea nitrogen (UUN) on the study day. A metabolic cart study was obtained on the same day as the urine collection to estimate the daily MEE. Blood samples that were already obtained for clinical use were used for the measurement of biomarkers. Biomarkers of interest include prealbumin, procalcitonin, c-reactive protein, transferrin, and 3-methylhistidine.


Results: Sixteen patients have been enrolled and completed the study procedures. Two patients have been enrolled and not completed study procedures. The mean age of enrolled patients is 36.4 years old. Twelve of the enrolled patients had traumatic brain injuries and four had ischemic strokes. Preliminary results include a mean MEE of 2153 kcal and a mean mCrCl of 231 ml/min.


Conclusions: Enrollment expected to conclude in August of 2025. Final results and conclusion will be available by SCCM meeting.