title: Factors associated with aspirin resistance in patients premedicated with aspirin and clopidogrel for endovascular neurosurgery.
abstract: OBJECTIVE
  Antiplatelet therapy is critical to endovascular neurosurgical procedures. Some patients are aspirin-resistant nonresponders. We reviewed our endovascular neurosurgery patients who were premedicated with aspirin and clopidogrel and identified nonresponders to aspirin. Factors associated with aspirin resistance were determined.
  
  
  METHODS
  Consecutive endovascular neurosurgery patients were identified who were treated by the senior author (BLH) from December 2006 to October 2007 and who were premedicated with aspirin (325 mg) and clopidogrel (75 mg) for 7 days before the procedure. We retrospectively reviewed values from the platelet function analyzer-100 test (Dade-Behring, Deerfield, IL) from 1 day before the procedures. The following factors were evaluated for association with aspirin drug resistance: age, sex, body mass index, and smoking history; patients with hypertension, diabetes, coronary artery disease/ peripheral vascular disease, or hypercholesterolemia; disease pathology (aneurysm, intracranial stenosis, or extracranial stenosis); patients taking statins, beta-blockers, angiotensin-converting enzyme inhibitors/angiotensin receptor blockers, or antidepressants; and white blood cell count, hemoglobin, hematocrit, and platelet levels. A stepwise logistic model selection was used to select important factors and their interactions.
  
  
  RESULTS
  Eighty-one consecutive patients with the following interventions were included in the study: 35 aneurysm coilings (43%), 21 stent-assisted aneurysm coilings (26%), 13 carotid stent and angioplasties (16%), 7 intracranial stents and angioplasties (9%), and 5 extracranial vertebral artery stents and angioplasties (6%). Seventeen patients (21%) were nonresponders to aspirin. After model selection, the only factor associated with aspirin resistance was not taking an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker (P = 0.0348; odds ratio, 0.214; 95% confidence interval, 0.051-0.896).
  
  
  CONCLUSIONS
  Twenty-one percent of patients premedicated with aspirin and clopidogrel dual therapy for 7 days before endovascular neurosurgical procedures were nonresponders to aspirin. Patients not taking an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker may be at higher risk for aspirin drug resistance.
authors.affiliation: Department of Neurological Surgery, University of Florida, Gainesville, Florida 32610-0265, USA.
authors.forename: John F
authors.initials: JF
authors.lastname: Reavey-Cantwell
authors.forename: W Christopher
authors.initials: WC
authors.lastname: Fox
authors.forename: Brett D
authors.initials: BD
authors.lastname: Reichwage
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Fautheree
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Velat
authors.forename: Jobyna H
authors.initials: JH
authors.lastname: Whiting
authors.forename: Yueh-Yun
authors.initials: YY
authors.lastname: Chi
authors.forename: Brian L
authors.initials: BL
authors.lastname: Hoh
mesh_terms: D000368:Aged; D000783:Aneurysm / Q000188:drug therapy* / Q000601:surgery*; D001241:Aspirin / Q000009:adverse effects / Q000627:therapeutic use*; D002548:Cerebral Revascularization / Q000379:methods*; D000077144:Clopidogrel; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010975:Platelet Aggregation Inhibitors / Q000009:adverse effects / Q000627:therapeutic use*; D012189:Retrospective Studies; D013988:Ticlopidine / Q000031:analogs & derivatives* / Q000627:therapeutic use
chemical_list: D010975:Platelet Aggregation Inhibitors; D000077144:Clopidogrel; D013988:Ticlopidine; D001241:Aspirin