Studies on the suitability of a cyanine dye (Viher-Test) for indicator dilution technique and its application to the measurement of pulmonary artery and aortic flow.

The spectrum of a cyanine compound [Viher-Test (VT)] was recorded in distilled water, 5% glucose, 0.9% NaCl. The absorption maximum of these solutions was at 760 nm; after adding to plasma or blood the maximum was shifted to 785 nm. The time required for this spectral stabilization was less than 1 s at 37 degrees C for VT in H2O or glucose, it was slowed to 7 s at room temperature, and for VT in NaCl it was more than 30 s at 37 degrees C. VT binds to plasma proteins to at least 95%. The absorbance of VT in H2O (1000 mg/l) decreased by 1.0% per hour. Toxicity (LD50) of VT in H2O given i.v. in mice was 115 mg/kg body weight. Dye dilution determination of the flow in an artificial circulation with VT was within +/- 5% of direct measurements. Data indicate that VT is as suitable as Cardiogreen for indicator dilution technique using cuvette densitometer or reflection photometry. Simultaneous determinations of pulmonary artery and aortic flow from one dye bolus showed no significant difference on the average, but pulmonary artery flow diverged by up to +/- 25% from aortic flow due to incomplete mixing of dye and blood, respiratory changes of cardiac output or transient differences in right and left heart output.