title: The course of dynamic cerebral autoregulation during cervical internal carotid artery occlusion.
abstract: OBJECTIVE
  The selection of patients with cervical internal carotid artery occlusion (ICAO) for extracranial-intracranial bypass surgery is based on exhausted cerebrovascular reactivity to vasodilatory stimuli. However, a spontaneous increase in this reactivity can occur with time, questioning the ideal time for bypass surgery. In contrast, the natural course of dynamic cerebral autoregulation is not known in these patients.
  
  
  METHODS
  Patients with cervical ICAO were examined at baseline and after a mean interval of 15 months. Dynamic autoregulation was determined by transcranial Doppler sonography in both middle cerebral arteries via respiratory-induced 0.1-Hz oscillations (phase, available for n=47 patients) and correlation analysis between diastolic blood pressure and Doppler signal (index Dx, n=55 patients). Pre-defined cut-off values and repeatability measures of healthy controls were used to define significant individual changes in autoregulation.
  
  
  RESULTS
  Group mean comparisons between studies were not significant for any autoregulation parameter. The intraclass correlation coefficient between studies was high for phase (ipsilateral: 0.83; contralateral: 0.74), and moderate for Dx (ipsilateral: 0.63; contralateral: 0.35). There was no clear trend for an improvement across cut-off values. A significant individual improvement/deterioration in autoregulation occurred in 6%/6% for phase and 13%/9% for Dx.
  
  
  CONCLUSIONS
  Dynamic autoregulation only rarely improves during the course of ICAO. This finding should be considered when deciding for or against a policy of delaying extracranial-intracranial bypass surgery for reasons of a potentially improving hemodynamic status.
authors.affiliation: Department of Neurology, University of Freiburg, Germany. matthias.reinhard@uniklinik-freiburg.de
authors.forename: Matthias
authors.initials: M
authors.lastname: Reinhard
authors.forename: Markus
authors.initials: M
authors.lastname: Roth
authors.forename: Brigitte
authors.initials: B
authors.lastname: Guschlbauer
authors.forename: Marek
authors.initials: M
authors.lastname: Czosnyka
authors.forename: Jens
authors.initials: J
authors.lastname: Timmer
authors.forename: Cornelius
authors.initials: C
authors.lastname: Weiller
authors.forename: Andreas
authors.initials: A
authors.lastname: Hetzel
mesh_terms: D000368:Aged; D001921:Brain / Q000098:blood supply* / Q000503:physiopathology; D002340:Carotid Artery Diseases / Q000000981:diagnostic imaging / Q000503:physiopathology*; D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D008297:Male; D017585:Ultrasonography, Doppler, Transcranial