Cardiac Output (Fick’s Formula)

Fick Cardiac Output Calculator

VO₂ (Oxygen Consumption)

mL/min

Estimate: 125 × BSA (m²) if not measured

Hemoglobin (Hb)

g/dL

SaO₂ (Arterial O₂ Saturation)

SvO₂ (Mixed Venous O₂ Saturation)

Cardiac Output: –

–

Calculates cardiac output, cardiac index, and stroke volume.

Why Use

Assesses cardiac capacity and aids in hemodynamic assessment. Guides management in cardiogenic shock patients, specifically to assess effectiveness of fluid resuscitation, vasopressors, or inotropic support.

When to Use

Inpatients with suspected cardiogenic shock and a pulmonary artery catheter in place. For patients undergoing right or left heart catheterization to determine cardiac output (CO), cardiac index (CI), and stroke volume (SV).

Formula

CO (Cardiac Output), L/min = VO 2 / [(SaO 2 - SvO 2 ) x Hb x 13.4)], where VO 2 = 125 mL O 2 /min x BSA , and BSA = [(Height, cm x Weight, kg)/ 3,600 ] 1/2 In elderly patients (age ≥70 years), use 110 mL O 2 x BSA for VO 2 . CI (Cardiac Index), L/min/m 2 = CO/BSA SV (Stroke Volume), mL/beat = CO/HR Note: SaO 2 should be acquired by arterial blood gas measurement. SvO 2 should be acquired by mixed venous gas from pulmonary artery catheter. Formula assumes decimal values, not percentages (this calculator automatically converts to decimal values).

Pearls / Pitfalls

The two most widely used ways of calculating CO are Fick’s method and the thermodilution technique. Fick’s method is based on the principle that oxygen consumption is equal to the product of the organ’s blood flow (CO) and the difference in the concentration of the substance in the arterial and venous circulation (arterial-venous oxygen difference). Fick’s method is less reliable in patients with pulmonary hypertension, heart failure, or abnormal body habitus. The thermodilution technique is less reliable in patients with tricuspid regurgitation or intracardiac shunting.

Management

If CO or CI is low or decreasing, consider increasing fluid administration. If the patient is not fluid responsive, consider adding vasopressors (norEPINEPHrine, DOPamine) via a central line, and use the CO/CI to guide adjustment of vasopressors as per goals of resuscitation (CI >2.5, MAP >60).

More Information

Normal values: CO = 4.0-8.0 L/min CI = 2.5-4.0 L/min/m 2 SV = 60-100 mL/beat MAP ≥60 mmHg