Cardiac output

Cardiac output is the amount of blood pumped out by each side of the heart (each ventricle) in one minute. It is the combination of heart rate (HR) and the stroke volume (SV). Stroke volume is the volume of blood pumped out by each ventricle with each heartbeat.

A normal adult blood volume is about 5000ml and the entire blood supply passes through the body once each minute. Cardiac output varies with the demands of the body. It rises when when the heart beats faster or stroke volume is increased and it drops when either or both factors decrease.

By using normal resting heart rate (75 beats per minute) and stroke volume (70ml per beat) we can work out the average adult cardiac output.

      CO = HR (75beats/min) X SV (70ml/beat)

      CO = 5250 ml/min

Assessment of the cardiac output is important in determining the work that the heart is actually performing with respect to the rest of the cardiovascular system. If the cardiac output is too low, then the body is not being properly supplied with blood (heart failure), which can and will lead to life threatening problems if left unchecked.