A method for measurement of total circulating blood volume using indocyanine green

A method of measuring total circulating blood volume (TBV) using indocyanine green (ICG) dye was investigated in 7 dogs and 16 patients. Since concentration of injected ICG decreases exponentially from the circulating system after recirculation, concentration of the dye at the time of appearance (Cta) can be extrapolated by extending the slope of the dye dilution curve transcribed to a semi-logarithmic graph. TBV was calculated using the following formula: TBV = I/Cta, where I is the amount (mg) of ICG injected. Repeat measurements of TBV using ICG demonstrated good reproducibility (average coefficient of variation, 2.0%) and when compared to measurements made with Evans blue dye resulted in a correlation coefficient of 0.98 or more. We conclude that assessment of TBV using ICG is reliable and experimentally and clinically feasible.