Extracorporeal circulation: an overview

By Cristiano Antonino On Jun 5, 2023

The extracorporeal circulation allows oxygenation and pumping of the circulating blood during cardiac surgery generally performed with a stopped heart; the heart will be stopped, for example, to repair or replace a valve or ascending aorta or to perform bypasses

It may be necessary to stop extracorporeal circulation for short periods of time

During the absence of circulation, it will be necessary to protect the brain from probable ischaemic damage.

Selective cerebral perfusion under hypothermia will therefore be performed, directly perfusing the encephalon through the carotid arteries with blood at a lower than normal temperature.

This will reduce the risk of neurological complications, but does not completely eliminate it.

Extracorporeal circulation could lead to complications related to mal-perfusion of several orders

Of the organs involved, those at greatest risk are the kidneys and the encephalon, which would then trigger post-operative renal failure.

If kidney damage already persisted before the operation, there could be worsening following the operation, and then recourse to filtration and dialysis treatments will be necessary, which may be temporary and in some cases permanent.

In cases of aortic bypass surgery, the operation could be performed by beating heart without recourse to extracorporeal circulation.

However, this intervention cannot be performed in all cases.

How is extracorporeal circulation performed?

Blood will be taken from the right atrium or the hollow veins of the heart and diverted to the heart-lung machine where it will be filtered, oxygenated and returned to the patient at the level of the most distal part of the ascending aorta.

Through the use of special solutions, the heart will be stopped and its metabolism protected when it is not supplied with blood.

When the operation is complete, the heart will be perfused and start beating again.

The extracorporeal circulation will be suspended, allowing the heart and lungs to resume their normal functions.

In some open-heart operations, it may be necessary to stop the heart to repair the heart muscle, valves or other organs.

The heart-lung machine will allow the surgeon to stop the heart while preserving blood circulation.

The machine consists of a pump, which functions like the heart, and an oxygenator, which performs the functions of the lungs.

During a heart-lung bypass, poorly oxygenated blood is first diverted from the upper cavities of the heart and directed to the reservoir of the heart-lung machine.

The blood is then transferred to the oxygenator, which enriches the blood with oxygen.

Finally, a pump will return the blood to the patient’s arterial system, and the body can resume blood circulation.

Once the damage has been repaired, the heart can start beating again and the heart-lung machine will be removed.