title: Preoperative beta blocker use associated with cerebral ischemia during carotid endarterectomy.
abstract: OBJECTIVE
  Cerebral ischemia is a known complication of carotid cross-clamping during carotid endarterectomy. Selective intraluminal shunting for cerebral protection is not always effective and carries risks. The purpose of this study was to identify potentially modifiable risk factors for intraoperative cerebral ischemia and shunting during carotid endarterectomy.
  
  
  METHODS
  We performed an historical case-control chart review of primary carotid endarterectomies with electroencephalographic (EEG) monitoring and selective shunting. Randomized controls and cases that showed ischemic EEG changes and required shunting were matched by year of surgery and the presence or absence of a contralateral carotid occlusion. Detailed perioperative data were collected for all cases. Results were analyzed using the Mantel-Haenszel test, analysis of variance, and a multivariate logistic regression model.
  
  
  RESULTS
  Of 523 charts screened, 69 patients had experienced evidence of cerebral ischemia on clamping of the carotid and required shunting. These patients were more likely than their matched controls to have been receiving regular preoperative beta blockers (33/69 vs 18/69, respectively; P = 0.01; odds ratio [OR] 2.5; 95% confidence interval [CI] 1.2 to 5.1). Ipsilateral moderate carotid stenosis (60-80%) was also associated with increased risk. An adjusted multivariate regression model estimated an OR of 3.6 (95% CI 1.5 to 8.9; P = 0.005) for the association between use of a beta blocker and shunting. Intraoperative hemodynamic values were similar for the shunt and control groups as well as for patients receiving and not receiving preoperative beta blockers.
  
  
  CONCLUSIONS
  The current study found an association between regular preoperative use of beta blockers and intraoperative cerebral ischemia in patients undergoing carotid endarterectomy. This effect did not relate to intraoperative hemodynamics.
authors.affiliation: Department of Anesthesiology and Perioperative Medicine, Kingston General Hospital, Queen's University, 76 Stuart Street, Kingston, ON, K7L 2V7, Canada.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Florea
authors.forename: Janet
authors.initials: J
authors.lastname: van Vlymen
authors.forename: Samia
authors.initials: S
authors.lastname: Ali
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Day
authors.forename: Joel
authors.initials: J
authors.lastname: Parlow
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000009:adverse effects*; D000368:Aged; D002545:Brain Ischemia / Q000209:etiology; D016022:Case-Control Studies; D004569:Electroencephalography; D016894:Endarterectomy, Carotid / Q000009:adverse effects; D005260:Female; D006801:Humans; D007431:Intraoperative Complications / Q000209:etiology*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged
chemical_list: D000319:Adrenergic beta-Antagonists