Abstract TP421: Cerebral Blood Flow Dynamics and Head-of-Bed Changes in the Setting of Subarachnoid Hemorrhage

Background: Head-of-bed (HOB) elevation is usually restricted in patients with aneurysmal subarachnoid hemorrhage (SAH). This practice is believed to prevent cerebral hypoperfusion. Objective: The goal of this study is to correlate HOB changes (0 o and 90 o ) with cerebral blood flow using Trans-cranial Doppler (TCD) and thermal diffusion probe in SAH patients. Methods: Thirteen patients with SAH were prospectively enrolled in the study. Eight patients underwent placement of a thermal diffusion probe for regional CBF measurement in the same setting when placing a ventriculostomy. CBF values were measured by TCD alone (13 subjects) or concurrently with thermal diffusion probe (8 subjects) with the patients in a flat (0 o ) and upright sitting position (90 o ) at day 3, 7, and 10. Results: The average increase in blood flow velocity when changing HOB from 0 o to 90 o was 7.8% on day 3, 0.1% on day 7, and 13.1% on day 10. The middle cerebral artery had the least changes in velocity compared to the anterior cerebral and the posterior cerebral arteries. The average regional CBF measurement was 22.7 +/- 10.3 ml/100g/min in the supine position and 23.6 +/- 9.1 mg/100g/min in the sitting position. The changes were not statistically significant. No change in clinical exam was appreciated. None of the patients developed clinical cerebral vasospasm. Conclusion: Changing HOB position in the setting of SAH did not significantly affect either cerebral blood flow velocity or regional blood flow. This data suggests that early mobilization should be considered given the detrimental effects of prolonged bed rest.