Calculate cardiac index, cardiac output, and stroke volume index from heart rate, stroke volume, and body surface area. Classifies hemodynamic status.
The Cardiac Index Calculator computes cardiac output (CO), cardiac index (CI), and stroke volume index (SI) from basic hemodynamic parameters. By normalizing cardiac output to body surface area, the cardiac index allows meaningful comparison of cardiac performance across patients of different body sizes.
Cardiac index is a cornerstone of hemodynamic assessment in critical care, cardiology, and perioperative medicine. Normal CI ranges from 2.2 to 4.0 L/min/m², with values below 1.8 indicating cardiogenic shock and values above 5.0 suggesting hyperdynamic states such as sepsis or thyrotoxicosis.
This calculator also estimates systemic vascular resistance and provides comprehensive hemodynamic profiling, helping clinicians identify the etiology of hemodynamic compromise and guide targeted therapy including fluids, vasopressors, inotropes, or vasodilators. Check the example with realistic values before reporting. Use the steps shown to verify rounding and units. Cross-check this output using a known reference case. Use the example pattern when troubleshooting unexpected results. Validate that outputs match your chosen standards.
Cardiac output alone does not account for body size differences. A CO of 4.5 L/min may be normal for a small adult but inadequate for a large athletic male. The cardiac index normalizes CO to BSA, enabling standardized assessment of cardiac performance.
Understanding the relationship between CI, SVR, and volume status is essential for differentiating types of shock and selecting appropriate hemodynamic therapies.
CO = HR × SV / 1000 (L/min) BSA = √(Height × Weight / 3600) [Du Bois] CI = CO / BSA (L/min/m²) SI = SV / BSA (mL/m²) SVR = 80 × (MAP - CVP) / CO (dyn·s/cm⁵)
Result: CI 2.61 L/min/m² — Normal
CO = 72 × 70 / 1000 = 5.04 L/min. BSA = √(175 × 75 / 3600) = 1.93 m². CI = 5.04 / 1.93 = 2.61 L/min/m², which is within the normal range (2.2-4.0).
The cardiac index is one component of comprehensive hemodynamic profiling that includes preload assessment (CVP, PCWP), afterload (SVR), contractility (dP/dt), and oxygen delivery (DO₂). Integration of these parameters guides selection between fluids, vasopressors, inotropes, and vasodilators in the management of shock.
Cardiac index response to fluid challenge helps determine fluid responsiveness. A CI increase >15% after a fluid bolus suggests preload dependence. Dynamic parameters (pulse pressure variation, stroke volume variation) during mechanical ventilation have superior predictive value for fluid responsiveness compared to static preload measures.
The concept of cardiac index was introduced by André Cournand and Dickinson Richards, who shared the 1956 Nobel Prize for developing cardiac catheterization. Their work enabled direct measurement of cardiac output and revolutionized understanding of cardiovascular physiology and heart failure management.
Cardiac output (CO) is the total volume of blood pumped by the heart per minute (L/min). Cardiac index (CI) normalizes CO to body surface area (L/min/m²), allowing comparison across patients of different sizes. CI is the preferred clinical parameter.
Stroke volume can be measured by echocardiography (LVOT VTI method), pulmonary artery catheter (thermodilution), arterial waveform analysis (FloTrac, PiCCO), or estimated from biometric data. Echo-derived SV is the most common non-invasive method.
Low CI can result from reduced contractility (heart failure, MI), inadequate preload (hypovolemia, tamponade), excessive afterload (aortic stenosis, hypertension), or arrhythmias. The treatment depends on the underlying cause.
CI >4.0 can be physiologic (exercise, pregnancy) or pathologic (sepsis, anemia, thyrotoxicosis, AV fistula, liver cirrhosis). High-output states often have low SVR and may still cause organ hypoperfusion in distributive shock.
BSA better reflects metabolic rate and oxygen consumption than weight alone. Since cardiac output exists to meet metabolic demands, normalizing to BSA provides a more physiologically meaningful index of cardiac performance adequacy.
The Du Bois formula may be less accurate in obese patients, children, or those with extremes of body habitus. Alternative formulas (Mosteller, Haycock) exist for specific populations. For clinical CI calculations, the differences are generally small.