title: Impaired cerebrovascular reactivity in the early phase of subarachnoid hemorrhage in good clinical grade patients does not predict vasospasm.
abstract: OBJECTIVE
  Subarachnoid hemorrhage (SAH) alters cerebrovascular reactivity (CVR) to carbon dioxide (CO2), which may be related to an increased risk of delayed ischemic neurological deficits (DINDs). We report the results of bedside CVR testing in the acute phase of SAH in good clinical grade patients without established vasospasm or signs of DIND.
  
  
  METHODS
  Eighteen patients with SAH and 26 healthy subjects underwent CVR testing using transcranial Doppler with standardized changes in CO₂. None of the patients had clinical or radiological evidence of vasospasm or DIND at time of testing. A CVR index was calculated as the change in the middle cerebral artery blood flow velocity (MCAv) divided by the change in the end-tidal CO₂partial pressure (PCO₂), ∆ MCAv/Δ PCO₂, and values were compared with controls.
  
  
  RESULTS
  SAH patients had lower CVR when compared with normal controls (p = 0.0001 and p = 0.0094, respectively). Impaired CVR was not correlated with future vasospasm (p = 0.2).
  
  
  CONCLUSIONS
  Patients with SAH had significantly lower CVR indexes compared with healthy controls. Although impaired CVR was present in 50 % of the patients early after SAH, no correlation with later occurrence of DINDs was found.
authors.affiliation: Division of Neurosurgery, Department of Surgery, Sunnybrook Health Sciences Centre, University of Toronto, 2075 Bayview Avenue, Room A1-37, Toronto, ON, M4N 3M5, Canada, leo.dacosta@sunnybrook.ca.
authors.forename: Leodante
authors.initials: L
authors.lastname: da Costa
authors.forename: David
authors.initials: D
authors.lastname: Houlden
authors.forename: Gordon
authors.initials: G
authors.lastname: Rubenfeld
authors.forename: Michael
authors.initials: M
authors.lastname: Tymianski
authors.forename: Joseph
authors.initials: J
authors.lastname: Fisher
authors.forename: Jorn
authors.initials: J
authors.lastname: Fierstra
mesh_terms: D002545:Brain Ischemia / Q000000981:diagnostic imaging / Q000209:etiology / Q000503:physiopathology; D002245:Carbon Dioxide / Q000097:blood; D002560:Cerebrovascular Circulation / Q000502:physiology*; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010313:Partial Pressure; D011237:Predictive Value of Tests; D012720:Severity of Illness Index; D013345:Subarachnoid Hemorrhage / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D017585:Ultrasonography, Doppler, Transcranial; D020301:Vasospasm, Intracranial / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology*
chemical_list: D002245:Carbon Dioxide