Spontaneous Variability of Cardiac Output in the Dog

Abstract

A method was described for serial determinations of cardiac output in anesthetized or normal dogs using Rose Bengal as the slowly excreted substance in the dye dilution technique. Results indicate the cardiac output fluctuates spontaneously and unpre-dictably in dogs under sodium pentobarbital anesthesia as well as in trained, unanesthetized dogs. The application of para-aminohippuric acid to the direct Fick method has facilitated measurements of cardiac output over periods of time limited only by the rate at which simultaneous arterial and mixed venous blood samples may be drawn. Multiple measurements by this technique indicate that fluctuations in the canine cardiac output from moment to moment are of magnitudes equal to or greater than those seen over more extended periods of time.