Quantifying Glomerular Filtration Rates: Kidney Function Analysis Method and Apparatus

Acute Kidney Injury (AKI) remains a vexing clinical problem resulting in unacceptably high patient mortality, development of chronic kidney disease and accelerated progression to end stage kidney disease. Although clinical risks factors for developing AKI have been identified, there is no reasonable surveillance technique (“biomarker”) to definitively and rapidly diagnose and determine the extent of severity of AKI in any patient. Since patient outcomes correlate with the extent of injury, and effective therapy requires early intervention, the ability to rapidly diagnose and stratify patients by their level of kidney injury is paramount for clinical progress in this field. Therefore, FAST BioMedical is developing and characterizing an optical measurement technique utilizing a novel minimally invasive Ratiometric Fluorescence Device (RFD) that can rapidly, accurately, and repetitively quantify kidney function, the measured glomerular filtration rate (mGFR), independent of serum or urinary measurements. A sub-millimeter optical fiber, that delivers excitation light and collects fluorescent emissions, is inserted into a peripheral or central venous access via commercial intravenous catheters. A mixture of two fluorescent dextrans of different sizes and distinct fluorophores, a small freely kidney filterable “reporter” molecule and large non-filterable plasma volume “marker” molecules, is infused as a bolus, excited sequentially by light-emitting diodes, and in vivo signals detected and quantified by photomultiplier tubes. The patented quantitative ratiometric technique, by utilizing two fluorescent reporter molecules, minimizes the inherent limitations of intensity fluorescence determinations and allows for rapid and accurate determinations of mGFR and plasma volume. Utilization of plasma fluorescent detection allows for the use of a two compartment model thus markedly minimizing the time needed for measuring GFR by eliminating extracellular space distribution of the filterable molecule.