Evaluation of a New Cuvette Densitometer for Determination of Cardiac Output

Quantitation of cardiac output by the Stewart-Hamilton method will have extended usefulness if the accuracy of measuring the concentration of Evans blue dye in whole blood is established. Cardiac outputs by this method have been compared in dogs with outputs by the rotameter and the Fick method. The constant-flow photometer (Friedlich) was used initially, but certain difficulties in its use led to the development of a new cuvette densitometer. Comparisons using both these instruments gave average variations of plus 7.0 per cent and minus 5.4 per cent from the reference methods. With proper caution cardiac outputs in dogs can be accurately obtained from dye dilution curves in whole blood.