Effect of Protein and Electrolyte on the Spectral Stabilization of Concentrated Solutions of Indocyanine Green

Abstract

In the measurement of flow by dye-dilution techniques, the optical density of the dyeblood mixture must stabilize in the interval between dilution and detection if an accurate measurement of flow is to be obtained. For many years indocyanine green (ICG), the most widely used dye in hemodynamic studies, was thought to sbabilize within 1.5 to 2 sec after dilution (1). However, a recent study ( 2 ) failed to reproduce these results. Another study ( 3 ) concluded that slow optical stabilization of ICG results in marked overestimation of flow if appearance times of the dilution curves are under 6 sec, a common occurrence in many applications. Others (4) have also found errors suggestive of slow stabilization. Since multiple potential sources of error complicate these studies, and since the good agreement reported between direct flow measurements and values determined by ICG (5-7) involved long stabilization times, we studied the optical stabilization of ICG direutly in order to define the circumstances in which this could cause errors in flow measurement.Materials and Methods. Concentrated solutions of ICG2 at 1 mg/ml were prepared in media varying in protein and ionic composition, shown in detail in Fig. 2, by adding various solutions to aliquots of a 2.5 mg/ml solution of ICG in (the aqueous diluent supplied. Pllasma from fasted dogs, anticoagulated with ACD or heparin, was used with or without sodium phosphate buffers. 1Thk study was supported in lyart by Public Health Service Grant l3L 08068 and gmnts from the Gradiuate Schiod of the University of Minnesota and the Minnesota Heart Association. 2Oardiogren dye, lots 222 and 658, Hynson, Wevtcott land Dunning, Inc., Bldtimo1re, MD.Changes in optical densilty (OD) of ICG after dilution in plasma were continuously measured on a split-beam, dual-wavelength recording spectr~photometer.~ Mixing-dilution was accomplished with la plunger a~sernbly,~ mounted on top of l a 1 cm cuvette, consisting of a cup on a spring-loaded shaft which on rapid depression into the cuvetrte, created turbulence, mixing the ICG in the cup with the plasma in the cuvette before re-emerging. Nonspecific OD changes, for example due to bubble formation during mixingd ilultion, necessitated use of the dualwavelength mode (8). In this mode light beams at two wavelengths are alternately passed through the cuvette, and the difference in OD of the cuvetlte contents at these wavelengths is recorded. Wavelengths used were 805 nm, which is in the region used for detection of ICG in hemdynamitc applications, and 890 nm, where ICG has no significant absorbsance (9-1 1 ) . The degree of compensation for nonspecific OD changes thus achieved was (assessed by repeating the plunger depressions after the OD had stabilized following diilution. With this method, the duration of the mixing artifact was always less than 1.6 sec, so that OD cbanges due only to ICG could be measured 2 sec after dilution.Results are reported in percentage of stabilized OD because ist was found that a variable amount of dye was emptied fr...

Hepatic Elimination of Indocyanine Green with Special Reference to Distribution Kinetics and the Influence of Plasma Protein Binding

“…ICG (Fig. 1) is purchased as a powder (Cardio-green; Hynson, Westcott & Dunning Products, Becton Dickinson Microbiology Systems, Cockeysville, USA) which is soluble in highly distilled water (Tripp et al 1973). The purification process leaves small amounts of NaI in the powder (Lutty 1978).…”

“…It is highly hydrophobic and lipophilic, even compared to other cholephilic anions (Tazuma et al 1988), and this may be the reason why ICG does not pass dialysis membranes (Baker 1966;Gentile et al 1985). ICG is green with an absorption maximum of 780 nM in distilled water and methanol, 800 nm in an albumin containing solution, and 805 nm in plasma (Sutterer et al 1966;Gathje et al 1970;Tripp et al 1973;Valerie 1973;Gentile et al 1985). It is difficult to obtain a stable and simple solution of ICG in protein free buffer (Baker 1966;Sutterer et al 1966;Gathje et al 1970;Simmons & Shephard 1971;Valerie 1973;Bjornsson et al 1982;Rappaport & Thiessen 1982;Heintz et al 1986;Green 1992).…”

“…ICG binds to proteins in plasma. Early studies (Cherrick et al 1960;Sutterer et al 1966;Gathje et al 1970;Tripp et al 1973;Valerie 1973;Bjornsson et al 1982) noted that albumin stabilized ICG in aqueous solutions. As judged by gel electrophoresis of plasma proteins it appeared (Cherrick et al 1960) that 95% of ICG is bound to albumin.…”

Influence of plasma protein on the inhibitory effects of indocyanine green and bromcresol green on pulmonary prostaglandin E1 extraction

“…This possibility is supported by the observation that species differences exist in the major indocyanine green binding protein fractions (Baker, 1966). One factor which might need to be considered when comparing different studies is that the physico-chemical properties of the dye and the rate of protein binding can be influenced by the solute composition of the indocyanine green dye solution infused (Baker, 1966;Tripp et al, 1973;Landsman et al, 1976).…”

Comparison of Renal Blood Flow and Transit Times Measured by Means of 99mTc-Labelled Erythrocytes and Indocyanine Green in Humans with Normal and Diseased Kidneys

“…The use of Sparling's (1961) method for calibration and patient's renal curves of approximately the same height strongly minimizes errors due to variations in the extinction of the dye. Distortions from Beer's law due to temperature differences, inappropriate solvent (Saunders et al, 1970;Simmons & Shephard, 1971;Tripp, Cohen, Gerash & Fox, 1973) or the presence of labelled erythrocytes in the IG solution, should affect the calibration curves to a comparable extent.…”