Cardiac Index Calculator

Cardiac Index equals Cardiac Output divided by Body Surface Area

Solution

—
Share:

What Is the Cardiac Index?

The Cardiac Index (CI) normalizes cardiac output to body surface area, providing a size-adjusted measure of cardiac performance. By dividing cardiac output (liters per minute) by body surface area (square meters), clinicians obtain a value that allows meaningful comparison across patients of different body sizes.

Worked Example

An ICU patient has a cardiac output of 5.0 L/min measured by thermodilution and a body surface area of 1.8 m². Using the formula CI = Q / BSA, the cardiac index is 5.0 / 1.8 = 2.78 L/min/m². This falls within the normal range of 2.5–4.0 L/min/m², indicating adequate cardiac performance for the patient's body size.

Normal Values and Clinical Significance

A normal Cardiac Index ranges from 2.5 to 4.0 L/min/m². Values below 2.2 L/min/m² may suggest cardiogenic shock or severe heart failure, while elevated values above 4.0 L/min/m² can be seen in high-output states such as sepsis, thyrotoxicosis, or severe anemia. Serial CI monitoring in the ICU guides fluid therapy, inotrope titration, and overall hemodynamic management.

Frequently Asked Questions

How is Cardiac Index different from Cardiac Output?

Cardiac output measures the total volume of blood pumped per minute, while the Cardiac Index adjusts that value for body size. A cardiac output of 4 L/min may be adequate for a small adult but insufficient for a larger person. CI provides a standardized comparison.

What BSA formula should I use?

The most commonly used BSA formula is the Du Bois formula: BSA = 0.007184 × height(cm)^0.725 × weight(kg)^0.425. Our Body Surface Area calculator on this site supports multiple BSA formulas.

When is CI monitoring most important?

CI monitoring is critical in intensive care settings, particularly for patients in shock, those on vasoactive medications, post-cardiac surgery patients, and anyone with severe heart failure requiring hemodynamic optimization.

Related Sites