Cardiac Output Calculator - HR x SV, LVOT, or Fick

A cardiac output calculator turns the volume of blood the left ventricle pumps per minute into a single L/min number, so the same bedside worksheet, the same echo report, and the same Swan-Ganz tracing can be compared on the same scale. The page covers the HR x SV formula, the LVOT Doppler continuity equation, the Fick principle, the adult reference range, and the limits of any single L/min value on its own.

• • Bedside HR x SV check: Drop in a measured heart rate and stroke volume, and read the L/min result next to the same worksheet the ICU team is using.
• • Echo and cath lab: Use the LVOT Doppler branch with a measured LVOT diameter, LVOT VTI, and heart rate to return the same L/min value the report quotes.
• • Fick principle and cardiac catheterisation: Use the Fick branch with oxygen uptake and the arterial minus venous O2 content difference from a mixed venous sample and an ABG.

The result is a planning estimate, and the final decision about whether a given L/min value calls for fluids, inotropes, or a different line of treatment sits with the clinical team that has the full haemodynamic picture in front of it.

The size-normalisation step the cardiac output calculator uses to return a cardiac index in L/min/m^2 is the same step the Body Surface Area Calculator uses to return BSA in m^2 from height and weight.

The form works in three short steps. It reads the inputs from the branch you selected, computes the CO in L/min, and divides by the body surface area to also return a cardiac index in L/min/m^2 with a severity band.

• HR: Heart rate in bpm, the number of beats per minute at the time the CO or echo was measured.
• SV: Stroke volume in mL, the blood volume ejected by one heartbeat, from echo, MRI, or a Swan-Ganz derived value.
• LVOT_diameter: Left-ventricular outflow tract inner-edge diameter in cm at the aortic annulus on a parasternal long-axis view.
• BSA: Body surface area in m^2, computed from height and weight with Haycock, Mosteller, or DuBois, the divisor for cardiac index.

The arithmetic is small. The hard part is choosing the right branch. A wide A-V O2 difference drops the Fick CO. A small LVOT diameter squared compounds into a large change in the LVOT CO. All three BSA formulas agree within a few percent on a healthy adult.

According to StatPearls Physiology Cardiac Output, cardiac output is the volume of blood the left ventricle pumps per minute, the normal resting adult value is 4.0 to 8.0 L/min, and CO rises from 5 L/min at rest to about 25 L/min during heavy exercise in healthy adults.

According to StatPearls Calculating Fick Cardiac Output, cardiac output equals oxygen uptake in mL O2 per minute divided by the arterial minus venous oxygen content difference in mL O2 per litre of blood, which is the same Fick branch the calculator supports through its VO2 and A-V O2 content inputs.

The same L/min value the cardiac output calculator returns also feeds the L/min/m^2 number the Cardiac Index returns, since the indexed form is just CO divided by BSA.

Four concepts drive the result. Naming them keeps the L/min value from being read as a single lab number, which it is not.

The most important distinction is between cardiac output and cardiac index. CO is the raw L/min number, while CI is the same value divided by BSA, so the L/min/m^2 value can be compared across body sizes, ages, and studies.

The heart rate input is one of the two numbers in the HR x SV CO branch, and the ECG Heart Rate Calculator returns the rate in beats per minute from a 10-second strip or an R-R interval.

The form works from the data the bedside team, the echo lab, or the cath lab already has. Type the value that was actually measured.

1. 1 Pick the cardiac output source: Choose HR x SV for the bedside workflow, LVOT Doppler for the echo report, Fick for the cath lab and blood-gas workflow, or Direct if the L/min value is already in hand.
2. 2 Type the cardiac output inputs: Type the heart rate and stroke volume for HR x SV, the LVOT diameter, LVOT VTI, and heart rate for LVOT, the VO2, arterial O2, and venous O2 for Fick, or the L/min value for Direct.
3. 3 Enter height and weight: Type the patient's height in cm and weight in kg so the body surface area can be computed from the selected formula and the form can also return the cardiac index in L/min/m^2.
4. 4 Pick the BSA formula: Use Haycock as the default for haemodynamic worksheets. Switch to Mosteller or DuBois if the comparison chart uses a different formula.

A reader with HR 70, SV 70 mL, height 170 cm, weight 70 kg on Haycock BSA can read CO 4.90 L/min, CI 2.69 L/min/m^2, and severity band Normal adult on the same row.

The LVOT Doppler branch uses the same continuity-equation step the Aortic Valve Area Calculator uses to return aortic valve area from LVOT diameter and LVOT VTI.

A small form that turns the HR x SV, LVOT, Fick, and Direct inputs into a single L/min value with a cardiac index alongside has practical advantages.

• • Four input paths in one form: A single dropdown moves between HR x SV, LVOT Doppler, Fick, and Direct CO, so the same form covers the bedside, the echo lab, the cath lab, and the clinic worksheet.
• • Cardiac index alongside cardiac output: The same entry also returns a cardiac index in L/min/m^2, so the bedside team can quote both the raw L/min and the size-normalised value without re-entering the height and weight.
• • Three BSA formulas in one form: Haycock, Mosteller, and DuBois are all available, so the cardiac index can be aligned with the worksheet where the value will be written.
• • Severity band on the result: The 4.0 L/min lower band, the 4.0 to 8.0 L/min adult range, and the elevated range above 8.0 L/min are returned as a clear label on the result panel.

The form is also useful as a teaching aid. The side-by-side display of CO, CI, and BSA makes the normalisation step visible.

A measured L/min value sits next to a longer cardiovascular risk picture, and the Arterial Age Calculator returns a vascular age from the same lipid and blood-pressure inputs a haemodynamic workup is already collecting.

Several factors shape the cardiac output. The most important ones sit inside the form.

• • The form does not measure cardiac output. It turns the entered inputs into a L/min value, so the final clinical decision depends on how the CO was measured and what the rest of the haemodynamic picture looks like.
• • It does not replace MAP, SVR, central venous pressure, or the rest of the sepsis or shock workup, and it should not be used as a stand-alone resuscitation trigger.

The reference range is a starting point, not a hard threshold. Read the value next to the full haemodynamic picture and the trend over time.

According to ASEcho practice guidelines on valve disease and LVOT Doppler, cardiac output is computed by multiplying the LVOT velocity-time integral by the LVOT cross-sectional area, the same continuity-equation step the cardiac output calculator uses for the LVOT Doppler input.

A low CO in a septic or shock workup pairs with a metabolic read, and the Anion Gap Calculator returns the gap from sodium, chloride, and bicarbonate on the same patient.