FICK CARDIAC OUTPUT

Assessment of cardiac output is an integral part in the treatment of pulmonary hypertension and heart failure.  The accuracy of the thermodilution method in patients with low cardiac output or severe tricuspid regurgitation has been questioned.  In these cases the use of the Fick method of calculating cardiac output is much more accurate.  This method, though, is rarely used due to the cumbersome calculations and blood samples that are required to utilize this method.

Fick cardiac output ( CO ) calculation is considered the “gold standard” for determining cardiac output.  The Fick CO requires knowing the oxygen consumption or VO2.  Fick CO is calculated using blood oxygen content CaO2 and CvO2.

Adolph Fick first described the Fick principle in 1870  The Fick principle assumed that the rate at which oxygen is consumed is a functionof the rate of blood flows and the rate of oxygen pick up by the red blood cells.

EQUATION FOR FICK CO

        Fick CO=   O2 Consumption   ml/min     = L/min

                            ( CaO2-CvO2 ) 10         

      VO2 = 125 x  BSA

       Normal VO2 =  125 x 2 = 250 ml O2/min 

                      CaO2 = ( 1.36 x Hgb x SaO2 ) 

        CvO2 = ( 1.36 x Hgb x SvO2 )

CaO2 is the oxygen concentration of arterial blood and CvO2 is the oxygen concentration of  venous blood.