From PAC thermodilution, echo, or Fick method
Enter cardiac output (0.5-20 L/min).
Use our BSA calculator if unknown
Enter BSA (0.5-3.5 m²).
For stroke volume index calculation
For SVR index estimation
Cardiac Index
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⚠️ Medical Disclaimer: This calculator is for educational reference only. All hemodynamic assessments must be made by a licensed physician with full clinical context. Cardiac output measurement requires validated clinical equipment.
Sources & Methodology
Cardiac index formula and hemodynamic classifications per AHA/ACC guidelines and standard critical care medicine references.
American Heart Association / ACC — Hemodynamic Monitoring Guidelines
Standard CI normal ranges and cardiogenic shock definitions. heart.org
Guyton & Hall — Textbook of Medical Physiology, 14th Ed.
Foundational reference for cardiac output, cardiac index, and hemodynamic physiology.
Society of Critical Care Medicine (SCCM) — Hemodynamic Monitoring
ICU hemodynamic targets and cardiogenic shock management protocols. sccm.org
CI (L/min/m2) = CO (L/min) / BSA (m2)
SVI (mL/beat/m2) = CI / HR x 1000
BSA (Mosteller): sqrt(Height cm x Weight kg / 3600)
Normal CI: 2.5-4.0 L/min/m2
SVI (mL/beat/m2) = CI / HR x 1000
BSA (Mosteller): sqrt(Height cm x Weight kg / 3600)
Normal CI: 2.5-4.0 L/min/m2
CI = CO / BSA
Example: CO 5.0 L/min, BSA 1.8 m2.
CI = 5.0 / 1.8 = 2.78 L/min/m2 (Normal range 2.5-4.0).
With HR 80 bpm: SVI = 2.78 / 80 x 1000 = 34.7 mL/beat/m2 (Normal 25-45).
CI = 5.0 / 1.8 = 2.78 L/min/m2 (Normal range 2.5-4.0).
With HR 80 bpm: SVI = 2.78 / 80 x 1000 = 34.7 mL/beat/m2 (Normal 25-45).
Last reviewed: April 2026
How Is Cardiac Index Calculated?
Cardiac Index normalizes cardiac output to the patient's body size, enabling comparison across individuals regardless of height and weight. A cardiac output of 4.5 L/min is normal for a small person (BSA 1.5 m2, CI = 3.0) but represents a low cardiac output state for a large person (BSA 2.2 m2, CI = 2.05). CI removes this ambiguity by indexing to BSA.
In clinical practice, CI is measured via pulmonary artery catheter (thermodilution), transpulmonary thermodilution (PiCCO), echocardiography, or the Fick principle. It is a core parameter in managing cardiogenic shock, guiding vasopressor and inotrope titration, and assessing response to therapy.
Cardiac Index Classification Table
| CI (L/min/m2) | Classification | Clinical Significance |
|---|---|---|
| Below 1.8 | Severe cardiogenic shock | Immediate mechanical/pharmacologic support required |
| 1.8-2.2 | Cardiogenic shock | Inotropes, vasopressors, consider MCS |
| 2.2-2.5 | Borderline low | Monitor closely; compensated low output state |
| 2.5-4.0 | Normal | Adequate cardiac function for most adults |
| Above 4.0 | Hyperdynamic / high-output | Sepsis, pregnancy, hyperthyroidism, AV fistula |
Stroke Volume Index and Hemodynamic Context
Stroke Volume Index (SVI = CI / HR x 1000) provides additional insight into whether low CI is due to pump failure (low SVI despite normal HR) or rate-related (low HR with preserved SVI). Normal SVI is 25-45 mL/beat/m2. SVI below 25 suggests ventricular dysfunction or severe hypovolemia.
💡 Forrester Classification: In acute MI, hemodynamic subsets are defined by CI and pulmonary capillary wedge pressure (PCWP). Subset IV (CI below 2.2, PCWP above 18) has highest mortality and requires aggressive intervention. CI alone does not capture the full picture — always interpret alongside filling pressures and mixed venous oxygen saturation.
Frequently Asked Questions
CI = Cardiac Output / BSA. It normalizes CO by body size, allowing comparison across patients. Normal CI is 2.5-4.0 L/min/m2.
Normal adult CI is 2.5-4.0 L/min/m2. Below 2.2 = cardiogenic shock. Below 1.8 = severe cardiogenic shock. Above 4.0 = hyperdynamic state (sepsis, pregnancy, hyperthyroidism).
CI = CO (L/min) / BSA (m2). Example: CO 5.0 L/min, BSA 1.8 m2: CI = 2.78 L/min/m2. BSA is calculated from height and weight using the Mosteller formula.
CO (cardiac output) is total blood pumped per minute in L/min. CI normalizes CO by BSA. A CO of 4.5 L/min is normal for a small person but low for a large person; CI removes this ambiguity.
Most commonly by thermodilution via pulmonary artery catheter, or transpulmonary thermodilution (PiCCO). Also by echocardiography (stroke volume x HR) or Fick method (O2 consumption / AVO2 difference).
CI below 2.2 L/min/m2 with MAP below 65 mmHg or SBP below 90 mmHg defines cardiogenic shock. CI below 1.8 is severe — requires inotropes, vasopressors, and consideration of mechanical circulatory support (IABP, Impella, ECMO).
CI above 4.0 occurs in septic shock (high CO despite low SVR), pregnancy, hyperthyroidism, severe anemia, AV fistulas, and high-output heart failure. Despite high CI, organ perfusion can still be inadequate if SVR is very low.
SVI = CI / HR x 1000. Normal: 25-45 mL/beat/m2. Low SVI indicates poor LV function or low preload. Distinguishes pump failure from rate-related causes of low CI.
Fick CO = O2 Consumption / (Arterial O2 content - Venous O2 content). Gold standard for CO in cardiac cath labs. Normal O2 consumption ~250 mL/min at rest.
No. CI calculation requires validated CO measurement from clinical equipment. This is for educational reference only. All hemodynamic management requires physician assessment.
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