Hepatic blood flow measurements and indocyanine green kinetics in a chronic dog model

The objective of this study was to compare hepatic blood flow measurements using ultrasonic flow probes and ICG in a conscious dog model and to evaluate whether ICG can be used to estimate relative change in hepatic blood flow. Seven mongrel dogs (3 M, 4 F, BW = 21 +/- 1.8 kg, Hct = 0.39 +/- 0.05) were used in the study. Catheters were surgically inserted into carotid artery and portal, hepatic and jugular vein. Transit-time ultrasonic flow probes were implanted around the portal vein and hepatic artery. After two weeks of recovery, a single i.v. bolus dose of ICG (0.5 mg/kg) was administered to each dog. The disposition profiles for ICG in the four catheters were measured for 15 minutes and the hepatic blood flow reading from the probes recorded. Jugular vein ICG blood clearance (Cl = 5.9 +/- 1.1 ml/min/kg) was low compared to the electronically measured hepatic blood flow rate (Q = 27.8 +/- 9.1 ml/min/kg). Extraction ratios (E = 0.15 +/- 0.05) estimated using data from the inlet and the outlet of the liver were consistent with the clearance values, suggesting that ICG is not highly extracted by dog livers. Three dogs were used in experiments where liver blood flow was increased by food intake. Consistent with characteristics of low extraction ratio drugs, ICG was insensitive to blood flow changes while there was an overall increase in electronically measured liver blood flow of 30%.(ABSTRACT TRUNCATED AT 250 WORDS)