Vascular brain infarction (VBI) occurs in 67% of patients undergoing TEVAR. Overt stroke occurs in 13% of these patients and 88% of patients suffer from neurocognitive impairment.

Cerebral air embolisation during the stent-graft deployment phase of TEVAR may be a cause of VBI. Standard treatment to de-air stent-grafts is through the use of a saline flush.

This study aims to investigate whether carbon-dioxide or saline is the better fluid to de-air TEVAR stent-grafts prior to insertion in to the patient and compare VBI rate in the carbon-dioxide group and saline group.

Thoracic endovascular aortic repair (TEVAR) is the re-lining of the thoracic aorta to prevent life threatening haemorrhage and death from rupture. This involves a small cut in the femoral artery in the groin and under imaging guidance, the insertion of wires and a stent into the thoracic aorta.

Prior to insertion into the patient, stents are flushed with saline to remove air and prevent air reaching the brain that can cause a form of brain injury known as vascular brain infarction (VBI). However, our preliminary clinical data suggests that saline flushing is not effective at de-airing stent-grafts used in TEVAR.

Carbon-dioxide has been used extensively in cardiac surgery to displace air from the chest cavity to prevent peri-procedural cerebral air embolisation. We hypothesise that flushing the stent-grafts with carbon-dioxide may be better at removing air from the stent-grafts than saline flush.

Patients undergoing TEVAR will be approached to participate in this study. After written consent is obtained, participants will be randomised to undergo (TEVAR) with carbon dioxide or saline flushing of stent-grafts. Pre-operatively, participants will undergo extensive neurocognitive testing, and a baseline blood test. Intra-operatively, participants will undergo continuous transcranial doppler monitoring (TCD) of the middle cerebral artery (MCA) to look for cerebral air embolisation at stent-graft deployment phase of TEVAR. Blood testing pre-op, immediately post op, and 24 hours post op will be taken to measure for biomarkers of brain injury. Post-operatively, participants will undergo another diffusion-weighted brain MRI within 72 hours post-procedure, stroke and delirium assessment at day 1, 3 and day 7 +/- day of discharge, and at 6-weeks and 6-month follow-up.

Inclusion Criteria:

• All participants suitable for TEVAR with capacity to consent

Exclusion Criteria:

• Participants who lack capacity to consent
• Contraindications to MRI such as pacemaker
• Pregnant participants
• Participants who do not wish to participate
• Participants <18yrs

Data requests can be made to the corresponding author and make on a case by case basis

10 years

These will be reviewed on a case by case basis

Participants will be blinded to treatment allocation. Assessment of TCD embolic data, DW-MRI scan reporting and neurological and neurocognitive assessment will be carried out by blinded trained assessors.