Plasma elimination of indocyanine green in the intact pig after bolus injection and during constant infusion: Comparison of spectrophotometry and high-pressure liquid chromatography for concentration analysis,

Abstract

Indocyanine green is used to estimate liver blood flow rate and hepatic intrinsic clearance. However, its use as a test substance for studies of liver function has been limited by two puzzling kinetic observations: a biexponential plasma decay after bolus injection with an extremely slow late phase and an apparently steadily decreasing clearance value during constant infusion. These observations have been made with spectrophotometric concentration analysis. In anesthetized 30- to 40-kg pigs, we examined plasma concentration curves of indocyanine green after intravenous bolus injection and during long-term infusion. We compared spectrophotometry with high-pressure liquid chromatography for measurement of plasma indocyanine green concentration. In freshly prepared commercially available indocyanine green, high-pressure liquid chromatography could separately measure two fractions, the genuine indocyanine green (97% to 99% of total) and an in vitro degradation product (1% to 3%). Because their spectra were nearly identical, these fractions could not be distinguished by spectrophotometry. After intravenous administration both fractions were identified in the plasma by high-pressure liquid chromatography. In the first series (n = 6) 25 mg of indocyanine green was injected intravenously for 5 min. When analyzed by high-pressure liquid chromatography, the genuine indocyanine green plasma concentration decay was biexponential with rate constants 0.196 +/- 0.021 (mean +/- S.E.M., n = 6) and 0.0372 +/- 0.0064 min-1. The degradation product of indocyanine green decayed almost monoexponentially, with a rate constant of 0.0093 +/- 0.0002 min-1. With spectrophotometry a biexponential decay was observed with rate constants 0.130 +/- 0.012 and 0.0095 +/- 0.0001 min-1. The biexponential decay of indocyanine green after spectrophotometry was the result of codetermination of the two fractions: genuine indocyanine green was responsible for initial phase, and the degradation product of indocyanine green was responsible for the late phase. In the second series (n = 9), indocyanine green was administered as a constant intravenous infusion. From 90 to 240 min the intrinsic hepatic clearance of genuine indocyanine green did not change detectably with time. In contrast, the degradation product of indocyanine green never reached steady-state concentrations. Because of code-termination of these two indocyanine green fractions, the apparent intrinsic hepatic clearance of indocyanine green estimated from spectrophotometry was steadily decreasing by 8.9% +/- 1% per hour of its initial value. At the same time estimation of liver plasma flow rate based on Fick's principle was not affected by the choice of analytical methodology. These observations indicate that high-pressure liquid chromatography is superior to spectrophotometry for kinetic analysis of indocyanine green elimination.

Hepatic Blood Flow and Splanchnic Oxygen Consumption in Patients With Liver Failure. Effect of High–Volume Plasmapheresis

“…Analyses. Analyses of D-sorbitol by enzymatic method 2 and ICG by high-performance liquid chromatography 14 have been previously described. ET-1 and ET-3 were determined after solid-phase extraction of plasma with use of SepPak C18 cartridges (Waters, Milford, MA) as described earlier.…”

Effects of adrenaline on lactate, glucose, lipid and protein metabolism in the placebo controlled bilaterally perfused human leg

“…Blood flow of the legs was determined using continuous infusion of ICG. Samples from the femoral artery and vein were taken in triplicate at the end of each period for measurements of ICG (Jorfeldt & Rutberg 1990, Ott et al 1993, Gjedsted et al 2007) and haematocrit (Minutes: 160,170 and 180 together with 340,350,360). Mean arterial and venous concentrations were used for calculations.…”

Forearm and leg amino acid metabolism in the basal state and during combined insulin and amino acid stimulation after a 3‐day fast

“…Plasma concentration of amino acids was determined using the HPLC technique (Biotek Kontron Instruments autosampler 465, System 265 and fluorescence detector SFM 25; Bio-Tek Kontron Instruments, Basel, Switzerland) with pre-column O-phthaldehyde derivatization, after deproteinizing the blood samples with 10% 5-sulphosalicylic acid (Jones & Gilligan 1983). Plasma ICG was determined by spectrophotometric analysis (Ott et al 1993). Blood and urine urea was measured by the urease-Berthelot method (Fawcett & Scott 1960).…”