NASGBI Project Grant
A pilot study of bilateral BIS monitoring (BBIS) after subarachnoid haemorrhage: will it help to diagnose vasospasm?
Dr John Andrzejowski
Background:
Subarachnoid haemorrhage (SAH) is a type of bleed into the brain that accounts for 10% of strokes in the UK. The average age of victims is about 55 years old. It is caused by a rupture of a defect/fault (an aneurysm) in the wall of one of the arteries within the brain. About 15% of patients do not survive the initial bleed. Survivors usually undergo surgical 'clipping' or have multiple 'coils' of very fine wire placed into the aneurysm under X-ray control. Both these procedures 'secure' the aneurysm from further rupture.
Subsequent recovery can still be threatened by complications, one of which is known as Vasospasm (VS); this occurs maximally between day 3 and 14 post bleed. VS results in many of the arteries to the brain going into 'spasm'. This leads to a decrease in blood & oxygen getting to part or all of the brain, often leading to further stroke or disability; together known as delayed cerebral ischaemia (DCI). It occurs in up to 50% of cases of SAH and is deemed to be the causative factor for disability in about 40% of cases and death in about 30%.
Detection of VS is essentially a clinical one. Patients' develop an altered conscious level, or a decrease power on one side of the body or changes in speech and behaviour. Once suspected, treatment of VS employs aggressive fluid hydration of the patient and maintenance of a higher than normal blood pressure that 'squeezes' the blood up to the brain. Overtreatment can lead to serious side effects, thus the need for accurate and timely diagnosis.
The Bispectral (BIS) index is a monitor used during anaesthesia for assessing how asleep the patient is by analysing brain waves through a strip of sticky electrodes applied to the forehead. There is evidence that this monitor detects decreased blood supply to the brain. It is non-invasive and very quick to apply and interpret. We have extensive experience of its use both in operating theatres and in Neurointensive care. A 'bilateral' version has recently been released that looks at both sides of the brain simultaneously. It may detect changes in brain circulation that the one-sided
sensor would miss.
Aims & Methodology:
We intend to carry out an observational study that involves placing a bilateral BIS electrode on patients admitted to our unit on Day 3 following SAH. Patients will have hourly neurological observations carried out. These look at conscious level and power in all limbs. This data will be collected on a daily basis. The sensor will be left in place for 10 days.
Expected outcome:
We wish to observe the BIS in all patients and see if any changes occur (particularly with respect to right versus left sided BIS) that correlate to the signs and symptoms of VS.
Implications:
If we detect changes then a second, larger trial can be designed to examine if BIS changes give advance warning of VS and allow earlier treatment, potentially affecting long term patient outcome and/or mortality.
