title: Bedside Xenon-CT Shows Lower CBF in SAH Patients with Impaired CBF Pressure Autoregulation as Defined by Pressure Reactivity Index (PRx).
abstract: Subarachnoid hemorrhage (SAH) is a disease with a high rate of unfavorable outcome, often related to delayed cerebral ischemia (DCI), i.e., ischemic injury that develops days-weeks after onset, with a multifactorial etiology. Disturbances in cerebral pressure autoregulation, the ability to maintain a steady cerebral blood flow (CBF), despite fluctuations in systemic blood pressure, have been suggested to play a role in the development of DCI. Pressure reactivity index (PRx) is a well-established measure of cerebral pressure autoregulation that has been used to study traumatic brain injury, but not extensively in SAH.
  
  
  
  To study the relation between PRx and CBF in SAH patients, and to examine if PRx can be used to predict DCI.
  
  
  
  Retrospective analysis of prospectively collected data. PRx was calculated as the correlation coefficient between mean arterial blood pressure (MABP) and intracranial pressure (ICP) in a 5 min moving window. CBF was measured using bedside Xenon-CT (Xe-CT). DCI was diagnosed clinically.
  
  
  
  47 poor-grade mechanically ventilated patients were studied. Patients with disturbed pressure autoregulation (high PRx values) had lower CBF, as measured by bedside Xe-CT; both in the early (day 0-3) and late (day 4-14) acute phase of the disease. PRx did not differ significantly between patients who developed DCI or not.
  
  
  
  In mechanically ventilated and sedated SAH patients, high PRx (more disturbed CBF pressure autoregulation) is associated with low CBF, both day 0-3 and day 4-14 after onset. The role of PRx as a monitoring tool in SAH patients needs further studying.
authors: Department of Neuroscience/Neurosurgery, Uppsala University, Uppsala, Sweden. ulf.johnson@neuro.uu.se.|Department of Surgical Sciences/Radiology, Uppsala University, Uppsala, Sweden. ulf.johnson@neuro.uu.se.
authors: Ulf
authors: U
authors: Johnson
authors: Department of Neuroscience/Neurosurgery, Uppsala University, Uppsala, Sweden.|Department of Surgical Sciences/Anesthesia and Intensive Care, Uppsala University, Uppsala, Sweden.
authors: Henrik
authors: H
authors: Engquist
authors: Department of Neuroscience/Neurosurgery, Uppsala University, Uppsala, Sweden.
authors: Tim
authors: T
authors: Howells
authors: Department of Neuroscience/Neurosurgery, Uppsala University, Uppsala, Sweden.
authors: Pelle
authors: P
authors: Nilsson
authors: Department of Neuroscience/Neurosurgery, Uppsala University, Uppsala, Sweden.
authors: Elisabeth
authors: E
authors: Ronne-Engström
authors: Department of Neuroscience/Neurosurgery, Uppsala University, Uppsala, Sweden.
authors: Anders
authors: A
authors: Lewén
authors: Department of Neuroscience/Neurosurgery, Uppsala University, Uppsala, Sweden.
authors: Elham
authors: E
authors: Rostami
authors: Department of Neuroscience/Neurosurgery, Uppsala University, Uppsala, Sweden.
authors: Per
authors: P
authors: Enblad
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D062186:Arterial Pressure / Q000502:physiology*; D002545:Brain Ischemia / Q000000981:diagnostic imaging / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D013345:Subarachnoid Hemorrhage / Q000000981:diagnostic imaging / Q000503:physiopathology*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014978:Xenon
chemical_list: D014978:Xenon
keywords: Cerebral blood flow; Cerebrovascular pressure reactivity; Hemorrhage; Monitoring; Subarachnoid; Xenon-CT