Abstract
A new method of serial determination of cardiac output has been employed to evaluate the cardiac function. It is based on the indocyanine green dye-dilution method with sampling from the systemic artery after injection of the dye into the right atrium. The purpose of the present study is to verify the reliability and reproducibility of this method, and to investigate the influence of cardiac glycoside and adrenergic β-receptor blockade upon the cardiac and renal functions, and also to determine the hemodynamic effect of electrical conversion of atrial fibrillation to sinus rhythm in patients with operated mitral stenosis. Part I. The Basic Studies for the Determination of Cardiac Output by Indocyanine Green-Dilution Method Materials and Methods. Indocyanine green in doses of I to 1.5 mg was injected into the right atrium through a 7F Lehman catheter inserted into the antecubital vein. Blood was sampled from the brachial or femoral artery through an indwelling arterial needle employing a Gilford constant withdrawal pump (Model 105S) and a cuvette densitometer (Model 1031R). The dye dilution curve was recorded on an 8-channel photographic recorder (Sanborn 4568A) with an electrocardiogram. The dye concentrations were replotted on a semilogarithmic paper. The curve was calibrated by whole blood and integrated sampling methods. The cardiac output was calculated according to Hamilton's formula. Two successive determinations of cardial indicies within 3 to 5 minutes were made in a total of 31 cases with or without heart disease. Results and Discussion: Fick and dye determination of cardiac output were carried out in 16 subjects. The average dye cardiac index was 2.74 ± 0.20 L/min/m2 and the Fick was 2.94 ± 0.23 L/min/m2. The correlation coefficient for Fick to dye was 0.88 (P <0.001). There was no significant difference between the mean values of these two groups. These results showed reliability of the dye method. The average cardiac index in the first determination of the two successive measurements within 3 to 5 minutes in 31 subjects was 2.86 ± 0.15 L/min/m2. The average in the second determination was 2.88 ± 0.16 L/min/m2. The percent difference between two successive determinations ranged from -13.3 to ± 10.5%. About 94% of all determinations were within ± 10% of the line of identity. The correlation coefficient was 0.99 (P <0.001). These results revealed good reproducibility of the dye-dilution method. The differences may be mainly due to the physiological changes rather than technical errors.
