Haemodynamic parameter
Cardiac index (CI) is a haemodynamic parameter that relates the cardiac output (CO) from left ventricle in one minute to body surface area (BSA),[1] thus relating heart performance to the size of the individual. The unit of measurement is litres per minute per square metre (L/min/m2).
Calculation
The index is usually calculated using the following formula:[citation needed]
![{\displaystyle {\text{CI}}={\frac {\text{CO}}{\text{BSA}}}={\frac {{\text{SV}}\times {\text{HR}}}{\text{BSA}}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/013ca28b8ae799d0bb4295e84cee54f063cf246c)
where
- CI
- Cardiac index
- BSA
- Body surface area
- SV
- Stroke volume
- HR
- Heart rate
- CO
- Cardiac output
Clinical significance
The normal range of cardiac index at rest is 2.6–4.2 L/min/m2.
The cardiac index is frequently measured and used in both intensive care medicine and cardiac intensive care. The CI is a useful marker of how well the heart is functioning as a pump by directly correlating the volume of blood pumped by the heart with an individual's body surface area.[citation needed]
If the CI falls acutely below 2.2 L/min/m2, the patient may be in cardiogenic shock.[citation needed]
References