The application of the hemoglobin saturation sensor and indocyanine green (ICG) for blood flow measurement

BACKGROUND: The aim in this study is to evaluate a new blood flow measurement applying a hemoglobin saturation sensor and indocyanine green (ICG) in circuit and animal models. METHODS: 1) In the basic study, the blood was mixed in a tube with ICG, and a near-infrared sensor was placed in this tube. The standard curve of the relationship between ICG concentration and optical density was obtained. 2) In the circuit model, the blood was circulated by the roller pump. ICG was injected in this circuit and its concentration was calculated from the change in optical density at 810 nm. Rate of flow was calculated based on the Fick's principle. The validity of this method was evaluated by Bland and Altman analysis. 3) In the animal model, a hemoglobin saturation sensor was inserted into three anesthetized dogs via the jugular vein, and iced ICG was injected for calculating cardiac output. Cardiac output was calculated by the same theory of the circuit model. The validity of this method was also evaluated by Bland and Altman analysis. RESULTS: 1) A standard curve was drawn from 11 different points (r2=0.99). 2) The calculated flow rate correlated well with the actual flow rate (r2=0.97). 3) The calculated cardiac output correlated well with results obtained with the thermodilution method. CONCLUSIONS: Application of a hemoglobin saturation sensor and ICG to blood flow measurement was reliable and useful in both circuit and animal models. This method may be clinically useful for measurement of blood flow.