Measurement of Cardiac Output in Man by Injection of Dye at a Constant Rate Into the Right Ventricle or Pulmonary Artery

Abstract

A method is described for the determination of the cardiac output in man by the injection of Evans blue dye (T-1824) at a constant rate into the right ventricle or pulmonary artery with continuous recording of the dye-dilution pattern by a cuvette oximeter connected to the radial artery. The method is simple to carry out and results can be quickly calculated. Evidence is presented which indicates that significant recirculation of dye does not occur prior to the establishment of an equilibrium or near-equilibrium concentration of dye in the radial-artery blood following such injections. Determinations of cardiac output by this constant-rate injection technique, by the Fick method and by the Hamilton method following the sudden single injection of dye were made in 22 studies on 17 subjects. Cardiac output values by the Fick method ranged from 1.7 to 7.7 l/minute/m2. There were no systematic differences between the 3 methods. Standard deviation of differences between the paired Fick and constant-rate dye_injection values was 10%, between sudden single and constant-rate dye-injection values was 16% and between Fick and sudden single dye-injection values was 16%. The average time intervals between these paired determinations were 5, 9 and 6 minutes, respectively. It is concluded that the constant-rate-injection version of the indicator-dilution technique is a reliable method for the measurement of cardiac output in man when the pulmonary artery or right ventricle is used as the injection site.