Indocyanine Green permits recording of the indicator-dilution curves for both diagnostic and research purposes independently of fluctuations in oxygen saturation. In the performance of dye dilution curves, a known amount of dye is usually injected as a single bolus as rapidly as possible via a cardiac catheter into selected sites in the vascular system. A recording instrument (oximeter or densitometer) is attached to a needle or catheter for sampling of the dye-blood mixture from a systematic arterial sampling site. 

Under sterile conditions, the Indocyanine Green for Injection USP powder should be dissolved with Sterile Water for Injection, USP, and the solution used within 6 hours after it is prepared. If a precipitate is present, discard the solution. The amount of solvent to be used can be calculated from the dosage form which follows. It is recommended that the syringe used for injection of the dye be rinsed with this diluent. Saline is used in all other parts of the catheterization procedure. 

This matter of rinsing the dye syringe with distilled water may not be critical, since it is known that an amount of sodium chloride sufficient to make an isotonic solution may be added to dye that has first been dissolved in distilled water. This procedure has been used for constant-rate injection techniques without precipitation of the dye. 

The usual doses of Indocyanine Green which have been used for dilution curves are as follows: 

    \- Adults-5 mg 
    \- Children-2.5 mg 
    \- Infants-1.25 mg 

These doses of the dye are usually injected in a 1-mL volume. An average of five dilution curves is required in the performance of a diagnostic cardiac catheterization. The total dose of dye injected should be kept below 2 mg/kg. 

### Calibrating Dye Curves: 

To quantitate the dilution curves, standard dilutions of Indocyanine Green in whole blood are made as follows: It is strongly recommended that the same dye that was used for the injections be used in the preparation of these standard dilutions. The most concentrated dye solution is made by accurately diluting 1 mL of the 5-mg/mL dye with 7 mL of distilled water. This concentration is then successively halved by diluting 4 mL of the previous concentration with 4 mL of distilled water. (If a 2.5 mg/mL concentration was used for the dilution curves, 1 mL of the 2.5 mg/mL dye is added to 3 mL of distilled water to make the most concentrated "standard' solution. This concentration is then successively halved by diluting 2. mL of the previous concentration with 2 mL of distilled water.) Then 0.2-mL portions (accurately measured from a calibrated syringe) of these dye solutions are added to 5-mL aliquots of the subject's blood, giving final concentrations of the dye in blood beginning with 24 mg/liter, approximately (actual concentration depends on the exact volume of dye added). This concentration is, of course, successively halved in the succeeding aliquots of the subject's blood. These aliquots of blood containing known amounts of dye, as well as a blank sample to which 0.2 mL of saline containing no dye has been added, are then passed through the detecting instrument and a calibration curve is constructed from the deflections recorded.