Simultaneous detection of deuterium oxide and indocyanine green in flowing blood

A spectrophotometer designed to measure simultaneously traces of deuterium oxide (12 mg.1-) and indocyanine green (0.12 mg.1-1) in flowing blood is described. Its symmetrical four-beam design enabled direct readings in optical density units to be obtained in the infrared region without interference due to atmospheric CO2 and water. This system was validated by the measures of pulmonary extravascular water in the rat in heart-lung preparations and in whole animals. An example of its application showed that, with this system, it was possible to evaluate correctly an alloxan edema in the rat a short time (105 min) after its induction. In these experiments lung water calculated by indicator curves represented 80% of the lung water content (r = 085, n = 10).