Cardiac Index (CI): Normalizes Cardiac Output (CO) to Body Surface Area (BSA).
Guidelines & Evidence
Clinical Details
Section 1
When to Use
When to Use
Assessment of cardiac output adjusted for body size (Body Surface Area).
Essential for identifying cardiogenic shock (CI < 2.2 L/min/m2).
Monitoring response to inotropic therapy or mechanical circulatory support.
Section 2
Formula & Logic
Formula
CI = CO / BSA
Where CO = Cardiac Output (L/min), BSA = Body Surface Area (m2).
Clinical Thresholds
Normal CI
2.5–4.0 L/min/m2
Cardiogenic Shock
< 2.2 L/min/m2
Severe Low Output
< 1.8 L/min/m2
Section 3
Pearls/Pitfalls
Why indexing matters
A cardiac output of 4.0 L/min might be normal for a small elderly woman (BSA 1.5 m2, CI 2.6) but would be dangerously low for a large young man (BSA 2.2 m2, CI 1.8). Always index to BSA for clinical decision-making.
Section 4
Next Steps
Complementary Calculators
Fick Cardiac Output
SVR Calculator
PVR Calculator
MAP Calculator
Stroke Volume Index
Section 5
Evidence Appraisal
Hemodynamic Standards
Catheterization of the heart in man with use of a flow-directed balloon-tipped catheter.
Swan HJ et al. • N Engl J Med.. 1970;The landmark paper introducing the Swan-Ganz catheter and standardized hemodynamic indexing.
