EVALUATION OF THE MICROSPHERE-METHOD FOR DETERMINATION OF CARDIAC-OUTPUT

Cardiac output was determined by means of radioactive microspheres, 15 ± 5 μm in diameter. Blood flow in the ascending aorta was measured by an electromagnetic flowmeter. In eight cats thirty-eight simultaneous measurements were made of cardiac output and aortic flow. The observations correlated well (r = 0.89), with a mean difference of 5.2% probably corresponding to coronary blood flow. Continuous flow recordings showed no alterations in aortic flow during the injections of microspheres; arterial blood pressure and heart rate remained unchanged even after six injections, each consisting of about 2 × 105 spheres per kg body weight. Tests for shunting of microspheres were performed and revealed shunt fractions in the systemic circulation of about 8% with no significant shunting through the lungs. The microsphere method for determining cardiac output is thought to be an accurate method, suitable for small and medium sized animals. © 1979 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.