Q: How the dynamic hepatic clearance test is measured?

Answer: The dynamic hepatic clearance test is also known as the indocyanine green plasma disappearance rate (ICG-PDR). LFT (liver enzymes) and hepatic protein synthesis has limited diagnostic sensitivity for hepatic dysfunction in ICU patients. ICG-PDR is found to be better correlated in critically ill patients.

Indocyanine green (ICG) (compound) is injected in the central venous catheter. Dose is 0.5 mg/kg. ICG is exclusively eliminated by the liver unconjugatedly into the bile and does not undergo enterohepatic recirculation. Its removal from the blood depends on liver blood flow, parenchymal cellular function, and biliary excretion.

Its elimination is expressed as the plasma disappearance rate (ICG-PDR) and  is measured non-invasively at the bedside by transcutaneous pulse densitometry with a finger clip. Normal values for ICG-PDR are considered to be more than 18% per minute. 


 References: 

1. Kimura S, Yoshioka T, Shibuya M, Sakano T, Tanaka R, Matsuyama S. Indocyanine green elimination rate detects hepatocellular dysfunction early in septic shock and correlates with survival. Crit Care Med. 2001;29:1159–1163.

2. Sakka SG, Reinhart K, Wegscheider K, Meier-Hellmann A. Comparison of cardiac output and circulatory blood volumes by transpulmonary thermo-dye dilution and transcutaneous indocyanine green measurement in critically ill patients. Chest. 2002;121:559–565.