Augmented renal clearance: a common and sustained finding in patients without renal impairment during the first seven days in ICU

Abstract

Introduction : Augmented renal clearance (ARC), commonly defined by an elevated urinary creatinine clearance (CL CR ), has been associated with sub-therapeutic antibiotic levels in the critically ill. Objectives : To determine the prevalence of and risk factors for ARC in patients without overt renal impairment on admission to the ICU. Methods : Prospective, multicentre study in four ICUs in Australia, Singapore, Hong Kong, and Portugal. Inclusion criteria: anticipated ICU stay N 24 hours; admission plasma creatinine b 120 μ mol/L; and no history of prior RRT or CKD. Eight-hour urinary CL CR measures were collected daily, with values ≥ 130 mL/min per 1.73m 2 being defined a priori as ARC. Demographic, physiological, therapeutic, and outcome data were also recorded prospectively. Mixed effects modeling was employed to account for varying study duration for individual participants. Results : Two hundred eighty-one patients contributed data, providing 1660 individual CL CR measurements. The mean age was 54.4 (16.7) years; mean APACHE II score, 16.0 (6.31); median ICU, stay 4 (2-10) days; and ICU mortality, 8.5%. Less than 10% were elective admissions. Overall, 65.1% manifested ARC on at least one occasion during the first 7 study days, most of whom did so on ≥ 50% of their CL CR measures. ARC was strongly associated with younger age, admission post-trauma, and lower modified SOFA scores. The presence of ARC on day 1 strongly predicated ( P = .019) ongoing elevated CL CR over the first week in the ICU. Conclusions : ARC is common in patients admitted to the ICU without overt renal impairment and is sustained throughout the first 7 days. This may significantly impact adequate drug dosing