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    Cardiac Output (Fick’s Formula)

    Calculates cardiac output, cardiac index, and stroke volume.
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    When to Use
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    Why 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).

    • 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.

    lbs
    in
    %
    %
    g/dL
    beats/min
    <70 years
    ≥70 years

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    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).

    Formula

    • 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 Ox 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

    Normal values:

    • CO = 4.0-8.0 L/min

    • CI = 2.5-4.0 L/min/m2

    • SV = 60-100 mL/beat

    • MAP ≥60 mmHg

    Dr. Adolf E. Fick

    About the Creator

    Adolf E. Fick, MD, (d. 1901) was a physiologist at the University of Zurich in Switzerland. Dr. Fick’s research focused primarily on physiology and medical physics.
    Content Contributors
    Reviewed By
    • On Chen, MD
    About the Creator
    Dr. Adolf E. Fick
    Content Contributors
    Reviewed By
    • On Chen, MD