INDOCYANINE GREEN: OBSERVATIONS ON ITS PHYSICAL PROPERTIES, PLASMA DECAY, AND HEPATIC EXTRACTION*

Abstract

Indocyanine green 1 (ICG) is a tricarbocyanine dye (Figure 1) which has been used in the indi- cator dilution technique for measuring cardiac output (1, 2).Animal studies (3) and prelimi- nary observations of human subjects (4, 5) have suggested that this dye may have characteristics that could make its uptake, storage, and excretion by the liver helpful indices of hepatic function.The present investigations were carried out to determine whether indocyanine green has proper- ties that may render it suitable for assessing liver function and hepatic blood flow in man.METHODS AND PROCEDURES Physical properties.Indocyanine green was prepared for intravenous administration by dissolving the dye in distilled water to a concentration of 5 mg per ml.Read- ings of dye concentration were made in a Beckman DU spectrophotometer at 815 m/1.Volume of distribution of radioiodinated human serum albumin 2 was compared with the initial volume of dis- tribution of ICG in 4 normal subjects.Each subject was given approximately 20 /Ac of the I3"-labeled albumin and 50 mg of ICG in a rapid intravenous injection.Ve- nous