Blowing carbon dioxide onto the heart to protect the brain during open heart surgery

Brain injury is common after open heart surgery and affects 6 out of every 10 people. Most people affected have mild symptoms, such as short-term confusion or memory problems. Rarely, brain injury can be more serious, for example a stroke. It has also been suggested that brain injury after open heart surgery may trigger dementia.

Surgeons believe the brain problems sometimes seen in patients after heart surgery are caused by tiny nitrogen-rich air bubbles in the blood, called gaseous micro-emboli. It’s thought that blowing carbon dioxide over the heart when it’s being operated on can reduce the amount of these tiny air bubbles getting into the blood stream, because carbon dioxide is heavier than air

Project aims

The aim of this project is to find out whether blowing carbon dioxide over the heart when it’s being operated on can reduce the amount of tiny air bubbles getting into the blood stream.

100 patients having open heart surgery at Bristol Heart Institute will take part in the study.

During their surgery, we will measure the number of tiny air bubbles in the middle cerebral artery, which takes blood to the brain, using a type of ultrasound scan. We will compare the number of tiny air bubbles in the middle cerebral artery when we blow carbon dioxide over the heart during surgery, with the number of tiny air bubbles when we blow air over the heart instead.

What we hope to achieve

This study will help us find out whether blowing carbon dioxide over the heart during open heart surgery is useful.

The results of this study will be looked at together with the results of a bigger study where we can scan people’s brains to see if it’s the bubbles causing damage to the brain, or something else.

We hope our research will help us understand what causes brain injury during open heart surgery, so it can be prevented.