Indicator dilution using a fluorescent indicator.

In vitro and in vivo indicator-dilution measurements are made with a fluorescent indicator and a novel detection system using a catheter containing a single optical fiber that carries both the exciting and returning fluorescent light. These fluorescent-dilution measurements are compared with simultaneous green dye-dilution measurements. The double-indicator-dilution measurement of extravascular lung water using heat and fluorescence is compared with gravimetric measurements. Also investigated is the sensitivity of the fluorescent measurement to changes in O2 saturation and hematocrit of the blood. An example of the measurement of a right-to-left heart shunt with this new indicator is given.