title: Bilateral failure of cerebral autoregulation is related to unfavorable outcome after subarachnoid hemorrhage.
abstract: BACKGROUND
  The extent of hemodynamic disturbances following subarachnoid hemorrhage (SAH) varies. We aim to determine the prognostic implications of unilateral and bilateral autoregulatory failure on delayed cerebral ischemia (DCI) and outcome.
  
  
  METHODS
  Ninety-eight patients with aneurysmal SAH were recruited. Autoregulation was assessed using systolic flow index-Sxa. Interhemispheric difference in autoregulation was calculated to assess the spatial distribution and symmetry of autoregulatory changes. Assessment of interhemispheric difference in autoregulation in combination with overall autoregulation was used to measure the extent of autoregulatory impairment. Patients were dichotomized by the presence of DCI and 3-month mRS.
  
  
  RESULTS
  Higher flow velocity and worse autoregulation (p < 0.0000001, 95 % CI 10.7-21.3 and p = 0.00001, 95 % CI 0.03-0.07 for difference in FV and Sxa, respectively) were found ipsilateral to the ischemic hemisphere or location of aneurysm (if no ischemia detected). DCI group had a higher interhemispheric difference of autoregulation than non-DCI group (p = 0.035, 95 % CI 0.003-0.08). 16/18 patients with unfavorable outcome vs. 17/72 with favorable outcome had overall poor autoregulation with low interhemispheric differences (p = 0.0013, χ (2)). Unilateral autoregulatory failure was seen on a median day 3, bilateral on day 4, and vasospasm was detected on day 6.
  
  
  CONCLUSIONS
  Unilateral autoregulation failure was seen in patients who developed DCI (worse ipsilateral to the ischemic hemisphere). Bilateral autoregulation failure was seen more frequently in patients with unfavorable outcome. Analysis of the temporal profile showed unilateral dysautoregulation as the primary event predisposing to DCI, which in selected cases led to bilateral failure and unfavorable outcomes.
authors: Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Hills Road, CB2 0QQ, Cambridge, UK, karol.budohoski@gmail.com.
authors: Karol P
authors: KP
authors: Budohoski
authors: Marek
authors: M
authors: Czosnyka
authors: Peter J
authors: PJ
authors: Kirkpatrick
authors: Matthias
authors: M
authors: Reinhard
authors: Georgios V
authors: GV
authors: Varsos
authors: Magdalena
authors: M
authors: Kasprowicz
authors: Mirosław
authors: M
authors: Ząbek
authors: John D
authors: JD
authors: Pickard
authors: Peter
authors: P
authors: Smielewski
mesh_terms: D000328:Adult; D000368:Aged; D015901:Angiography, Digital Subtraction; D002545:Brain Ischemia / Q000209:etiology / Q000503:physiopathology* / Q000628:therapy; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D013345:Subarachnoid Hemorrhage / Q000150:complications*; D017585:Ultrasonography, Doppler, Transcranial