[Measuring cardiac output in infants with the Fick principle via oxygen consumption: animal experiment and clinical results]

Abstract

The aim of this investigation was the validation of cardiac output measurement in children using the method of Fick with the help of a new equipment for the determination of oxygen uptake.

Methods: We compared the cardiac output measured with thermodilution with the calculated cardiac output using the method described by Fick in an animal model (11 dogs, mean weight 20 kg). For determining the cardiac output on Fick's principle oxygen uptake and oxygen content of the arterial and pulmonary-arterial blood was measured in the ventilated dogs. To examine the method of Fick in clinical routine we also determined oxygen uptake and arterial and central venous oxygen content in 5 children in the postoperative period after cardiac surgery with a mean weight of 8.5 kg. Cardiac output in the patients was calculated with the central venous and the pulmonary-arterial oxygen content. The two results were compared.

Results: The animal model showed a good correlation of cardiac output measurement on thermodilution and on Fick's method (alpha = 0.001, t-test of significance of correlation). With the method of Fick we found also reliable results at follow up in the clinical routine in the 5 children. The comparison of cardiac output calculated with the central venous oxygen content versus the pulmonary-arterial oxygen content shows a good correlation over all (r = 0.92). In some cases however we found profound differences.