Article by Ryan W. Stevens, PharmD, BCPS, and Nicholas A. Smith, PharmD, Pharmacy Times

“Whether practicing pharmacy in the ambulatory or inpatient setting, professionals devote a substantial amount of energy and time to appropriate dosing of medications for renal impairment. This is appropriate, considering that about 14% of the general population is affected by chronic kidney disease, and those with this disease likely have more frequent exposure to the health care system.1 However, considerably less attention has been focused on the opposite end of the spectrum, those patients who may exhibit a hyperdynamic state of renal clearance. This phenomenon is commonly referred to as augmented renal clearance (ARC), and only within the past decade has it begun to gain attention in the medical community.2 The definition of ARC varies in the literature with respect to actual filtration rate, duration of hyperdynamic filtration, and cutoff creatinine clearance (CrCl) values. The most widely accepted definition of ARC is a CrCl greater than 130 mL/min/1.73 m2. However, there is no consensus on grading or stratification of severity with escalating CrCl values.2

Much remains unknown regarding the mechanism of ARC. However, available evidence suggests that multiple changes to nephron physiology may be at play.2 One model proposes that systemic inflammation in critically ill patients results in vasodilation and reduction of systemic vascular resistance. This decrease in resistance, when coupled with the administration of intravenous fluids and increases in heart rate, leads to increased cardiac output, increasing renal preload. This hyperdynamic state results in the increased glomerular filtration rates seen in ARC.3 The incidence of ARC may be as high as 30% to 65% in critically ill patients with normal serum creatinine. The most consistent patient factors associated with ARC across multiple studies are an age of younger than 50 years and trauma.3,4 Other associated factors include being a man, modified sequential organ failure assessment (SOFA) scores ≤4, and lower Acute Physiology and Chronic Health Evaluation or Simplified Acute Physiology scores.2,4-6”

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