The HOME Study
Research type
Research Study
Full title
Hypobaric Oxygen during cardiopulmonary bypass to reduce gaseous Micro-Emboli during cardiac surgery: a randomised controlled trial
IRAS ID
305038
Contact name
Gianni Angelini
Contact email
Sponsor organisation
University Hospitals Bristol and Weston NHS Foundation Trust
ISRCTN Number
ISRCTN87042095
Duration of Study in the UK
2 years, 0 months, 0 days
Research summary
Research Summary - After heart surgery, some people can experience mild problems which affect their brain. These can include short-term difficulties with thinking, attention and memory. However, up to one in every five people continue to have difficulties with thinking, attention and memory one year after their surgery. \n\nDuring heart surgery the heart is stopped and a heart and lung machine is used to replicate the job of the heart, pumping oxygen-rich blood around the body. Surgeons believe that the brain problems that are sometimes seen in patients after heart surgery are caused by tiny nitrogen-rich air bubbles getting into the blood when it is being circulated in the heart and lung machine. These tiny air bubbles are known as gaseous micro-emboli (GME). \n\nRecent research has shown that using hypobaric oxygenation to reduce the dissolved gases in the blood greatly reduces GME formation during heart surgery. The resultant decrease in dissolved blood gases is expected to favour reabsorption of GMEs throughout the flow of blood within the circuit and lead to less brain problems after surgery. \n\nThe HOME study will test the hypothesis that using hypobaric oxygenation virtually eliminates GME formation in patients undergoing heart surgery. We will recruit 40 patients undergoing either coronary artery bypass graft (CABG) surgery or aortic valve surgery (with or without an associated CABG procedure). Each group will be randomised to have either hypobaric oxygenation or ‘conventional’ oxygenation in use during their heart surgery. During surgery, participants will have transcranial doppler ultrasound (TCDU) of the medial cerebral artery to measure the frequency and type of GME in circulation and cerebral blood flow. In addition, blood samples will be taken to analyse various biomarkers of brain injury (S100) and the inflammatory response (interleukins 6, 8 and 10 and TNF alpha). Research Results - This study looked at whether a new type of heart-lung machine oxygenator could reduce tiny air bubbles in the blood during heart surgery, which are thought to contribute to problems such as stroke or memory difficulties after surgery. Adults having planned heart surgery were randomly assigned to receive either the standard oxygenator or the new device, and ultrasound was used during surgery to measure air bubbles travelling to the brain. The study was stopped early after 25 participants because the new oxygenator did not reduce the number of air bubbles. No participant experienced a stroke or clear brain injury related to the study, although one participant died from unrelated complications. The results show that this new device did not provide the expected benefit and highlight the importance of carefully testing new medical devices in clinical trials before routine use.
REC name
North of Scotland Research Ethics Committee 1
REC reference
22/NS/0038
Date of REC Opinion
3 Apr 2022
REC opinion
Favourable Opinion