Comparison of Central and Peripheral Injection Sites in the Estimation of Cardiac Output by Dye Dilution Curves

The validity of cardiac output values from injections of indicator into a peripheral vein was tested. Dye dilution curves resulting from injections of Coomassie Blue dye alternately from peripheral and central sites were obtained in 20 subjects. Peripheral injections in which the dye was not flushed into the circulaton were in a large percentage of cases unreadable. In those which could be read the area under the curve was larger and the cardiac output on the average 8.5% lower than the values obtained from paired flushed injections. Curves from flushed peripheral injections had larger time components and lower concentration of indicator than those from paired central injections. There was no systematic difference in the cardiac output values derived from the two sites. In man, contamination of the primary curve by recirculation of dye does not seem to cause significant error when the indicator is flushed into the venous system in the manner described.