Effects of Donepezil on Regional Cerebral Blood Flow Following Aneurysmal Subarachnoid Haemorrhage

Introduction Aneurysmal subarachnoid hemorrhage (aSAH) is bleeding around the under surface of the brain caused by rupture of an aneurysm arising from a blood vessel. Stroke may occur in approximately one third of patients as a result of narrowing of the blood vessels around the brain, following aSAH. One theory as to why this may happen is because bleeding around the base of the brain damages particular cells (neurons) that control blood flow around the rest of the brain. These neurons may control blood flow by releasing a neurotransmitter called Acetyl Choline (ACh). Our hypothesis is that damage to these neurons may prevent the production of ACh, which then causes reduced blood flow and stroke if left untreated. By stimulating these neurons, we aim to investigate whether it is possible to improve the blood flow around brain and ultimately prevent strokes in patients following subarachnoid haemorrhage. Donepezil, a drug widely used in dementia, inhibits the brain's natural break down of ACh. We predict that by increasing the amount of Ach in these neurons, donepezil may improve blood flow to the brain, reducing the chance of developing stroke. Trial Protocol All patients admitted to St George's hospital with a confirmed aneurysmal subarachnoid haemorrhage between the ages of 18 and 85 years old will be invited to participate in the trial. The protocol has been designed to take place around the patients' aneurysm treatment, which is performed under general anesthesia (GA). Recruited participants will be anesthetized for their aneurysm treatment and then enter the study. All trial participants will have a Xenon CT scan under GA to assess brain blood flow prior to having treatment of their aneurysm. Patients randomized to donepezil treatment will receive a loading dose of 20mg via a feeding tube immediately after their Xenon scan. Patients in the control group will not receive the drug. All patients in the trial will undergo repeat Xenon perfusion scanning und