Abstract
Indocyanine green (ICG), a water-soluble tricarbocyanine dye, is rapidly removed from the circulation by the liver and secreted into the bile without conjugation (1–3). Currently, its major medical use is for indicator dilution studies during cardiac catheterization. However, its rapid excretion via the liver without significant extrahepatic removal (1–4) or enterohepatic circulation (1, 3) and freedom from the problems of local tissue necrosis or anaphyllaxis, which may occur with sulfobromophthalein (5), have prompted the increasing use of plasma ICG disappearance curves as a test of liver function. The most commonly used format for this purpose involves determination of the plasma fractional disappearance rate (k) or half-life (T 1/2) of ICG following the rapid intravenous injection of dye at a dose of 0.5 mg/kg body weight.
We present the results of plasma ICG disappearance studies in a large group of young, healthy normal volunteer subjects. The data unexpectedly indicate a significant difference in the plasma fractional ICG disappearance rates between normal men and women, which must be taken into account in interpreting similar studies in patients with either suspected or established liver disease.
Methods. Subjects studied. Plasma ICG disappearance studies were performed in 51 healthy normal individuals, ages 18–29, who had been admitted to the Clinical Center of the National Institutes of Health for the specific purpose of serving as control subjects for a variety of studies. Eighteen were men and 33 were women. All met strict, previously defined criteria for “normality” (6), and none had taken medications of any type within 4 weeks of the studies. Each of the 51 volunteers underwent plasma ICG disappearance studies employing a dose of 0.5 mg/kg body weight. In addition, 19 of the volunteers (9 men and 10 women) underwent three additional studies, employing indocyanine green doses of 2.0, 3.5, and 5.0 mg/kg.
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