Cardiac Output is the amount of blood that the heart pumps each minute. It is measured as a volume, in litres per minute.

We can measure cardiac output at the bedside with a Pulmonary Artery Catheter. It can also be measured during certain cardiac investigations such as a cardiac catheterization.

You may hear the term Cardiac Index used instead of Cardiac Output. We measure the cardiac output at the beside but convert the number to a "Cardiac Index" by dividing the cardiac output by the Body Surface Area. This makes the normal range for Cardiac Index the same no matter how big or small the individual. Thus, the Cardiac Index value is an easier number to interpret.

We use the Cardiac Output and Cardiac Index measurement the same way. We use them to help us to determine if the patient's heart is pumping enough blood. We use the number to fine tune some of our drug therapy.

Sometimes we talk about the patient's cardiac output being "too high" or "too low" even though we are not actually measuring the volume. When we use the word cardiac output in this manner, we are referring more to the concept that the patient's heart is not pumping enough blood (even though we don't know the absolute number).

A low blood pressure is a common cause for a low cardiac output. Sometime, the cardiac output is low because the heart is not pumping properly, and the low cardiac output may be the cause for the low blood pressure. The cardiac output can be low for many reasons including a low blood volume (the patient who needs fluid), heart damage, abnormal heart beats or certain medications.

A low cardiac output can reduce the delivery of oxygen and nutrients to other organs of the body. A low cardiac output can lead to failure of other organs. It is a common cause for kidney failure or failure of other organs.




Last Reviewed: October 23, 2014