Cardiac Output Calculator 2025: Complete Guide to CO, CI, SV, SVI
Cardiac Output (CO) is the volume of blood pumped by the heart per minute. It is a cornerstone of hemodynamic assessment in critical care, cardiology, and anesthesia. Our Cardiac Output Calculator supports three validated methods: Basic (HR × SV), Fick, and Doppler. This guide covers physiology, interpretation, and clinical application.
Why Measure Cardiac Output?
CO determines tissue perfusion. Low CO causes shock; high CO occurs in sepsis or hyperthyroidism. Normal CO: 4–8 L/min.
Key Parameters
1. Cardiac Output (CO)
- Formula: CO = HR × SV
- Units: L/min
- Normal: 4–8 L/min
2. Cardiac Index (CI)
- Formula: CI = CO / BSA
- Units: L/min/m²
- Normal: 2.5–4.0 L/min/m²
3. Stroke Volume (SV)
- Formula: SV = CO / HR
- Units: ml/beat
- Normal: 60–100 ml/beat
4. Stroke Volume Index (SVI)
- Formula: SVI = SV / BSA
- Units: ml/beat/m²
- Normal: 33–47 ml/beat/m²
Calculation Methods
1. Basic Method (HR × SV)
Simple, non-invasive. Requires HR and SV from echo or pulse contour.
2. Fick Method
Gold standard. Uses oxygen consumption and arteriovenous difference.
Formula: CO = VO₂ / (CaO₂ - CvO₂ × 10)
CaO₂ = (Hb × 1.34 × SaO₂) + (0.003 × PaO₂)
3. Doppler Echocardiography
Non-invasive. Uses LVOT area and VTI.
SV = π × (LVOT/2)² × VTI
Interpretation & Management
| CI (L/min/m²) | State | Action |
|---|---|---|
| <2.2 | Low Output | Inotropes, fluids, treat cause |
| 2.2–4.0 | Normal | Monitor |
| >4.0 | High Output | Treat sepsis, anemia, hyperthyroidism |
Clinical Scenarios
- Cardiogenic Shock: Low CO, high SVR
- Septic Shock: High CO, low SVR
- Heart Failure: Low SV, high preload
- Anesthesia: Monitor CO to guide fluids
Best Practices
- Use same method for serial measurements
- Measure at rest, avoid post-meal
- Validate with clinical signs
- Pair with MAP and lactate
- Reassess after intervention
Advanced Monitoring
- PAC (Swan-Ganz): Thermodilution
- PiCCO: Transpulmonary thermodilution
- Flotrac: Arterial waveform
- LiDCO: Lithium dilution
Limitations
- Fick: Assumes steady state
- Doppler: Operator-dependent
- Basic: Requires accurate SV
Integration with Other Tools
- BSA Calculator for CI
- Symptom Checker for shock
- Anesthesia Dose adjustment
FAQs
What is normal CI? 2.5–4.0 L/min/m²
When to use Fick? Research, pulmonary hypertension
Can children use this? Yes, adjust BSA
Conclusion
Accurate cardiac output assessment guides life-saving therapy. Use our 2025 Cardiac Output Calculator with the appropriate method. Always interpret in clinical context with preload, afterload, and contractility. Early intervention improves survival in shock and heart failure.
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