Bilateral Bispectral Index (BIS) Study

Subarachnoid hemorrhage (SAH) is a prevalent and morbid condition (45%-30 day mortality). One of the major causes of reduced cerebral blood flow (CBF) after initial SAH is cerebral vasospasm. Early treatment of cerebral vasospasm (< 2 hr) is necessary for improved neurologic outcome. Hence, there is significant interest in development of a monitor. The most common bedside diagnostic tool is Transcranial Doppler (TCD) which is controversial given its low sensitivity and specificity. TCD is not a continuous monitor and is user dependent. Many centers rely on Cerebral Angiography for diagnosis of vasospasm; however angiographic spasm does not correlate with outcome. EEG can detect changes in cerebral blood flow which precede clinical decline but is technically difficult to perform and not practical for continuous monitoring.

Processed EEG monitors have become somewhat popular in the operating setting for assessment of depth of anesthesia. The recent introduction of bilateral 4 channel disposable probes presents to opportunity to use EEG as a non-invasive continuous monitor for vasospasm. We propose a prospective observational study to assess real time changes in raw and processed EEG which we will correlate with clinical and radiologic evidence of vasospasm. Our primary clinical endpoint will be the determination of delayed cerebral ischemia. This modality could prove to be a significant clinical advantage for patients suffering from SAH.

Inclusion criteria

• Adult men or women of any age and ethnicity within 48 hours of subarachnoid hemorrhage (SAH)

Exclusion criteria

• Age < 18 years
• Greater than 48 hours past the initial hemorrhage
• Previous history of stroke of any etiology
• Inability to consent for themselves or have a proxy to consent for them (implied consent)