Is the cardiac output obtained from a Swan-Ganz catheter always zero?
OBJECTIVE
By means of a Swan-Ganz catheter cardiac output is calculated using the Stewart-Hamilton thermodilution equation. Assuming the body as a thermally isolated inert system, this equation theoretically always results in zero cardiac output.


METHODS
Using the first and second law of thermodynamics together with a few lines simple analysis this statement is proven.


CONCLUSIONS
It is at least a necessary condition for the application of the Stewart-Hamilton equation, that core body temperature is kept constant in a thermo- regulatory steady state.
Schramm
Wolfgang
W
Division of General Anesthesia and Intensive Care, Medical University of Vienna, Waehringer Guertel 18-20/9 i, 1090, Vienna, Austria. wolfgang.schramm@meduniwien.ac.at
D001795:Blood Pressure Determination / Q000379:methods*; D002302:Cardiac Output / Q000502:physiology*; D002407:Catheterization, Swan-Ganz / Q000379:methods*; D003198:Computer Simulation; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D006334:Heart Function Tests / Q000379:methods*; D006801:Humans; D008955:Models, Cardiovascular; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013815:Thermodilution / Q000379:methods*