Objective: To clarify cerebral blood flow dynamics during passive standing using ultrasound imaging in patients with acute subarachnoid hemorrhage in the cerebral vasospasm phase.

Methods: Transcranial color-coded sonography was used to evaluate cerebral blood flow dynamics in 13 patients with acute subarachnoid hemorrhage during rest in the supine position and 60° head-up tilt. For cerebral blood flow dynamics, blood flow velocities in the middle cerebral and internal carotid arteries (systolic, diastolic, and mean), blood flow volume in the internal carotid artery, and the ratio of systolic blood flow velocities in the middle cerebral and internal carotid arteries were measured.

Results: The mean blood flow velocity of the middle cerebral artery was significantly decreased with a 60°head-up tilt compared with that in the supine position.

Conclusion: In patients with acute subarachnoid hemorrhage, a 60° head-up tilt does not induce cerebral vasospasm but reduces the mean middle cerebral artery blood flow velocity.