Xenon-CT and transcranial Doppler in poor-grade or complicated aneurysmatic subarachnoid hemorrhage patients undergoing aggressive management of intracranial hypertension

Objective: To evaluate whether elevated flow velocimetry values are associated with critically reduced cerebral blood flow values in deeply sedated patients with acute aneurysmatic subarachnoid hemorrhage and in whom the detection of clinical vasospasm is not feasible. Design: Retrospective analysis of prospectively collected data. Setting: Neurosurgical and trauma patients in an intensive care unit in a regional hospital. Patients and participants: Twenty-nine patients in the acute phase following subarachnoid hemorrhage who were sedated and ventilated for elevated intracranial pressure, transcranial Doppler vasospasm, or respiratory failure and were studied with at least a coupled xenon-CT/transcranial Doppler study. Measurements and results: Combined measurement and comparison of cerebral blood flow by means of xenon-CT and of mean velocity by means of transcranial Doppler in middle cerebral artery territories. The case mix studied was consistent with patients' predominantly poor grade and with a complicated course. The results suggest that in sedated patients flow velocity and measured cortical mixed cerebral blood flow are not correlated, and, more specifically, that flow velocities values above 120 or 160 cm/s and Lindegaard index above 3 are not associated with an ischemic regional cerebral blood flow. Conversely, as many as 55% of the xenon-CT studies were associated with hyperemia. Conclusions: In patients with elevated intracranial pressure, mean middle cerebral artery flow velocity or Lindegaard Index does not help to detect critical cerebral blood flow nor elevated cerebral blood flow.