Limitations of Glomerular Filtration Rate Estimation in Pediatric Acute Kidney Injury

Determining the level of glomerular filtration is important for drug clearance, but it is challenging in the setting of developing kidneys, more so in those with acute kidney injury. Acute kidney injury (AKI) in children is a common problem and requires the attention of pediatric nephrologists. Typically, kidney function is measured by an estimate of the glomerular filtration rate (eGFR). While eGFR is used to determine drug dosing and clearance, there are limitations of utilizing this measure in pediatric AKI. In AKI, the recovery of kidney function is a dynamic process as the eGFR changes continuously. Approximately 2/3 of all drugs have renal elimination, but only very few drugs are cleared by GFR. Instead, most drugs are cleared in the tubules by organic anion and cation transporters, via active or passive transport. When there are AKI and acute tubular necrosis, these transport mechanisms do not function properly. The purpose of this chapter is to explain how drug dosing is determined in the growing child with AKI. The main focus will be on the methods and limitations of eGFR, and novel tools to estimate drug clearance.