title: Preoperative risk assessment for carotid occlusion by transcranial Doppler ultrasound.
abstract: OBJECTIVE
  An endovascular carotid balloon occlusion test with continuous intracranial monitoring by transcranial Doppler sonography was performed in 55 patients for prediction of tolerance of a required permanent occlusion of the carotid artery.
  
  
  METHODS
  Blood flow velocities of the ipsilateral middle cerebral artery during occlusion were recorded and compared with clinical tolerance during an occlusion test as well as with postoperative outcome after an eventual permanent occlusion. To stress the capacity of the cerebral circulation to tolerate the occlusion acetazolamide was injected before occlusion in all patients.
  
  
  RESULTS
  The onset of neurological symptoms during temporary occlusion was dependent on the percentage fall of mean blood flow velocity relative to baseline rather than on absolute flow velocities during the time of occlusion. Patients with a fall of mean flow velocity of less than 30% tolerated temporary and permanent occlusion, with the exception of two patients who developed an infarction due to thromboembolism after iatrogenic sacrifice of the carotid artery. Patients with a major decrease developed neurological symptoms during occlusion in 55% and, in cases of carotid ligation, a haemodynamic infarction occurred.
  
  
  CONCLUSIONS
  The results show that transcranial Doppler monitoring as a part of an endovascular balloon occlusion test may be a reliable technique for preoperative risk assessment for permanent occlusion of the carotid artery.
authors.affiliation: Department of Neurology, University of Bonn, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Schneweis
authors.forename: H
authors.initials: H
authors.lastname: Urbach
authors.forename: L
authors.initials: L
authors.lastname: Solymosi
authors.forename: F
authors.initials: F
authors.lastname: Ries
mesh_terms: D000328:Adult; D000368:Aged; D001157:Arterial Occlusive Diseases / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology; D001783:Blood Flow Velocity; D001921:Brain / Q000098:blood supply / Q000503:physiopathology; D002545:Brain Ischemia / Q000209:etiology / Q000503:physiopathology; D002343:Carotid Artery, Internal / Q000503:physiopathology* / Q000601:surgery*; D004569:Electroencephalography; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D012039:Regional Blood Flow; D018570:Risk Assessment; D014055:Tomography, Emission-Computed; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed; D017585:Ultrasonography, Doppler, Transcranial