Cardiac Output (Fick’s Formula)
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).
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.
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.
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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).
- CO (Cardiac Output), L/min = VO2/ [(SaO2 - SvO2) x Hb x 13.4)],
- where VO2 = 125 mL O2/min x BSA,
- and BSA = [(Height, cm x Weight, kg)/ 3,600 ]1/2
- In elderly patients (age ≥70 years), use 110 mL O2 x BSA for VO2.
- CI (Cardiac Index), L/min/m2 = CO/BSA
- SV (Stroke Volume), mL/beat = CO/HR
Note: SaO2 should be acquired by arterial blood gas measurement. SvO2 should be acquired by mixed venous gas from pulmonary artery catheter. Formula assumes decimal values, not percentages (this calculator automatically converts to decimal values).
Facts & Figures
CO = 4.0-8.0 L/min
CI = 2.5-4.0 L/min/m2
SV = 60-100 mL/beat
MAP ≥60 mmHg
Original/Primary ReferenceRagosta M. Textbook of Clinical Hemodynamics. Elsevier; 2017.
About the Creator
- Joseph Mizrahi, MD
- On Chen, MD