The study by Cherrick et al. investigates the physical properties, plasma decay, and hepatic extraction of indocyanine green (ICG) to assess its potential as an indicator for liver function and hepatic blood flow in humans. Key findings include: 1. **Physical Properties**: ICG is rapidly and completely bound to plasma proteins, primarily albumin. Its absorption spectrum in human serum albumin and plasma is similar, with a maximum absorption at 815 nm. Starch block electrophoresis shows that ICG is mainly bound to albumin. 2. **Plasma Decay**: ICG decays exponentially in plasma, with a rate of 18.5% per minute in normal subjects compared to 13.8% for sulfobromophthalein (BSP). In patients with cirrhosis, the correlation between ICG and BSP decay rates is strong (R = 0.92). 3. **Hepatic Extraction**: ICG is extracted exclusively by the liver, with extraction rates ranging from 0.59 to 0.83 in normal subjects. This makes it suitable for estimating hepatic blood flow using the Fick principle. 4. **Urine and Bile Excretion**: ICG is not excreted in urine and is excreted in bile in unconjugated form. It is not cleared by extrahepatic mechanisms. 5. **Safety**: ICG is nonirritating and does not cause adverse reactions upon single or repeated intravenous injections or infusions. 6. **Clinical Applications**: ICG is a reliable indicator for estimating hepatic blood flow, especially in mild liver disease, where BSP may not be effective due to poor hepatic extraction and excessive plasma retention. The study concludes that ICG is an ideal dye for assessing liver function and hepatic blood flow due to its rapid decay, high hepatic extraction, and lack of irritation.The study by Cherrick et al. investigates the physical properties, plasma decay, and hepatic extraction of indocyanine green (ICG) to assess its potential as an indicator for liver function and hepatic blood flow in humans. Key findings include: 1. **Physical Properties**: ICG is rapidly and completely bound to plasma proteins, primarily albumin. Its absorption spectrum in human serum albumin and plasma is similar, with a maximum absorption at 815 nm. Starch block electrophoresis shows that ICG is mainly bound to albumin. 2. **Plasma Decay**: ICG decays exponentially in plasma, with a rate of 18.5% per minute in normal subjects compared to 13.8% for sulfobromophthalein (BSP). In patients with cirrhosis, the correlation between ICG and BSP decay rates is strong (R = 0.92). 3. **Hepatic Extraction**: ICG is extracted exclusively by the liver, with extraction rates ranging from 0.59 to 0.83 in normal subjects. This makes it suitable for estimating hepatic blood flow using the Fick principle. 4. **Urine and Bile Excretion**: ICG is not excreted in urine and is excreted in bile in unconjugated form. It is not cleared by extrahepatic mechanisms. 5. **Safety**: ICG is nonirritating and does not cause adverse reactions upon single or repeated intravenous injections or infusions. 6. **Clinical Applications**: ICG is a reliable indicator for estimating hepatic blood flow, especially in mild liver disease, where BSP may not be effective due to poor hepatic extraction and excessive plasma retention. The study concludes that ICG is an ideal dye for assessing liver function and hepatic blood flow due to its rapid decay, high hepatic extraction, and lack of irritation.