Cardiac Output (Fick)

How to use it

1. 1

   Measure VO₂. Metabolic cart or assume 125 × BSA mL/min. In practice, estimated VO₂ introduces error.

2. 2

   Sample arterial and mixed venous blood. CaO₂ from radial arterial line ABG; CvO₂ from PA catheter. Central venous (ScvO₂) is an approximation.

3. 3

   Calculate. CO = VO₂ ÷ ((CaO₂ − CvO₂) × 10). Normal CO 4–8 L/min; CI = CO ÷ BSA (normal 2.2–4.0).

When to use it

Haemodynamic monitoring in ICU with PA catheter

Reference standard for CO measurement; rarely used in modern practice (largely replaced by echo/thermodilution).

Cardiac catheterisation lab

Fick CO used in right-heart cath to calculate PVR, SVR, and valve areas.

Not routine

Thermodilution (transpulmonary or PA catheter), transthoracic echo, or LiDCO are more practical in most ICU settings.