Optical behavior of indocyanine green dye in blood and in aqueous solution

Indocyanine green dye in the presence of sodium bisulfite exhibits a marked and extremely variable decrease in light absorption. Even the presence of the extremely minute quantity present in Lipo-Hepin, when used as an anticoagulant, will vitiate densitometer calibration. Spectrophotometric studies of aqueous solutions of dye in the presence of Lipo-Hepin do not show a marked change in light absorption of the dye. Stronger solutions of sodium bisulfite produced a marked decrease in light absorption over these wave lengths. Indocyanine green dye kept in a concentrated aqueous solution for periods up to 7 days shifts its peak absorption from 780 to 900 m μ. This shift in peak absorption is probably due to reversible polymolecular aggregation. As previously reported, fresh solutions of indocyanine green in plasma have an absorption maximum at 800 m μ. Peak absorption of aged dye-plasma solutions remains at 900 m μ.