Prevalence of Augmented Renal Clearance and Performance of Glomerular Filtration Estimates in Indigenous Australian Patients Requiring Intensive Care Admission

Abstract

Augmented renal clearance (ARC) refers to the enhanced renal excretion of circulating solute commonly demonstrated in numerous critically ill subgroups. This study aimed to describe the prevalence of ARC in critically ill Indigenous Australian patients and explore the accuracy of commonly employed mathematical estimates of glomerular filtration. We completed a single-centre, prospective, observational study in the intensive care unit (ICU), Alice Springs Hospital, Central Australia. Participants were critically ill adult Indigenous and non-Indigenous Australian patients with a urinary catheter in situ. Exclusion criteria were anuria, pregnancy or the requirement for renal replacement therapy. Daily eight-hour measured creatinine clearances (CrCLm) were collected throughout the ICU stay. ARC was defined by a CrCLm ≥130 ml/min/1.73 m2. The Cockcroft– Gault and Chronic Kidney Disease Epidemiology Collaboration equations were also used to calculate mathematical estimates for comparison. In total, 131 patients were recruited (97 Indigenous, 34 non-Indigenous) and 445 samples were collected. The median (range) CrCLm was 93.0 (5.14 to 205.2) and 90.4 (18.7 to 206.8) ml/min/1.73 m2 in Indigenous and non-Indigenous patients, respectively. Thirty-one of 97 (32%) Indigenous patients manifested ARC, compared to 7 of 34 (21%) non-Indigenous patients (P=0.21). Younger age, major surgery, higher baseline renal function and an absence of diabetes were all associated with ARC. Both mathematical estimates manifest limited accuracy. ARC was prevalent in critically ill Indigenous patients, which places them at significant risk of underdosing with renally excreted drugs. CrCLm should be obtained wherever possible to ensure accurate dosing.