Cardiox Liver Function Test Pivotal Trial

Indocyanine green (ICG) is a water-soluble, non-toxic tricarbocyanine dye, extracted principally by hepatic parenchymal cells and excreted almost entirely into the bile without enterohepatic circulation. Clinically, its elimination rate is used primarily to measure hepatic function and liver blood flow. ICG studies are also used in ophthalmic angiography and the determination of cardiac output. Beginning about 1959, the first human clinical studies were reported wherein an indocyanine green (ICG) bolus was injected into a vein, and then blood samples were withdrawn over a period of time and analyzed for ICG concentrations. This method is referred to hereinafter as the serial blood sampling method. These blood samples are sent to a clinical laboratory for a multi-step process of centrifuging, separation and spectrophotometric measurements of ICG levels. The laboratory-based measured levels of residual ICG levels are then used to determine the ICG clearance rate and R15 value or residual amount of dye remaining after 15 minutes, expressed as a percentage of the initial concentration. As an alternative to the time- and labor-consuming serial blood sampling method, a non-invasive technique was first reported nearly 20 years ago. In the first published clinical study, Ishigami reported the use of a pulse dye densitometry (PDD) method to transcutaneously detect the rate of clearance of ICG from the bloodstream to be referred to hereinafter as dynamic liver function testing. PDD expresses ICG elimination in terms of the indocyanine green plasma disappearance rate because only relative ICG concentration changes are assessed. The results of this noninvasive method have been shown to correlate with those obtained by the invasive method used in critically ill patients (hemodynamically unstable and stable), and in patients after liver surgery. ICG elimination rate after liver transplantation measured by either invasive or noninvasive ICG methods is widely used to evaluate graft function. Studies have shown that ICG elimination, measured on the day of transplantation, reflects graft function and can be used to predict graft viability and the expected survival of the patient. Sequential measurements of ICG elimination between days 0 and 28 of transplantation, have been shown to predict clinical outcome in the early postoperative period after living donor transplantation. All of the studies have shown that the ICG elimination rate is an accurate test for evaluating liver dysfunction, but lacks the ability to differentiate the underlying causes of the hepatic dysfunction. Unlike all currently existing PDD methods for performing liver function testing, LFT Dye Monitor System employs a more sensitive method for the transcutaneous measurement of ICG concentration level in the blood using NIR fluorescence, with a sensor that is attached loosely to the scaphoid fossa of the ear. Thus, the chemical properties of ICG dye to fluoresce when properly excited are used in the LFT system to enable much lower concentrations of ICG to be detectable.