Cardiac output measurements with thermodilution and radioactive microspheres. A comparative study in cats.

Thermodilution and radioactive microsphere measurements are both commonly used methods for determination of cardiac output in experimental animals. However, no comparison has been made of these methods for cardiac output determination, which is why this study was made. In cats 65 simultaneous measurements of cardiac output with the two methods were performed. No difference in mean values was found and the coefficient of correlation was 0.955 (P less than 0.001). Only eight out of the 65 measurements differed more than 10%. Thermodilution measurements are suitable for repeated determinations and when immediate data are wanted. On the other hand radioactive microsphere measurements are preferable when data on tissue blood flow and blood flow distribution are desired as well. The high correlation found seems to allow cardiac output measurements with these two methods to be grouped together.