Indocyanine green plasma clearance as a measure of changes in hepatic blood flow

The results from simultaneous measurements of indocyanine green (ICG) plasma clearance and hepatic blood flow (HBF) in subjects without hepatic dysfunction during changes in HBF induced pharmacologically or by food stimulation, are reported. A linear relation is established between the relative changes in HBF and that of ICG clearance (r = 0.94), but the changes are not identical, and therefore the changes in HBF cannot be accurately predicted from that of ICG plasma clearance. The reason behind the lack of identity of the changes lies in the complicated kinetics of dye removal by the liver. The hepatic venous catheterization technique is the only method when physiologically correct values for hepatic blood flow or changes therein are wanted.