Predictors of augmented renal clearance based on iohexol plasma clearance in critically ill children.

BACKGROUND: Augmented renal clearance (ARC) holds a risk of subtherapeutic drug concentrations. Knowledge of patient-, disease-, and therapy-related factors associated with ARC would allow predicting which patients would benefit from intensified dosing regimens. This study aimed to identify ARC predictors and to describe ARC time-course in critically ill children, using iohexol plasma clearance (CLiohexol) to measure glomerular filtration rate (GFR). METHODS: This is a retrospective analysis of data from the "IOHEXOL" study which validated GFR estimating formulas (eGFR) against CLiohexol. Critically ill children with normal serum creatinine were included, and CLiohexol was performed as soon as possible after pediatric intensive care unit (PICU) admission (CLiohexol1) and repeated (CLiohexol2) after 48-72 h whenever possible. ARC was defined as CLiohexol exceeding normal GFR for age plus two standard deviations. RESULTS: Eighty-five patients were included; 57% were postoperative patients. Median CLiohexol1 was 122 mL/min/1.73 m2 (IQR 75-152). Forty patients (47%) expressed ARC on CLiohexol1. Major surgery other than cardiac surgery and eGFR were found as independent predictors of ARC. An eGFR cut-off value of 99 mL/min/1.73 m2 and 140 mL/min/1.73 m2 was suggested to identify ARC in children under and above 2 years, respectively. ARC showed a tendency to persist on CLiohexol2. CONCLUSIONS: Our findings raise PICU clinician awareness about increased risk for ARC after major surgery and in patients with eGFR above age-specific thresholds. This knowledge enables identification of patients with an ARC risk profile who would potentially benefit from a dose increase at initiation of treatment to avoid underexposure. TRIAL REGISTRATION: ClinicalTrials.gov NCT05179564, registered retrospectively on January 5, 2022.