title: Carotid endarterectomy performed in the morning is associated with increased cerebral microembolization.
abstract: OBJECTIVE
  Platelet function exhibits circadian variation with highest levels of activity in the morning and plays a central role in arterial thrombotic events, including thrombotic stroke following carotid endarterectomy (CEA). Prior to the platelet-rich thrombus occluding the carotid artery, multiple embolic signals are detected in the middle cerebral artery using transcranial Doppler ultrasound. We hypothesized that patients undergoing CEA early in the day may be at an increased stroke risk and this would manifest as an increased postoperative embolic count.
  
  
  METHODS
  Data were collected prospectively on 235 patients undergoing primary CEA. Accurate start and finish times were recorded in addition to the number of postoperative emboli detected in the first three hours after CEA using transcranial Doppler (TCD) monitoring.
  
  
  RESULTS
  For operations finishing before midday, there was a 3.6-fold increase in the number of emboli detected relative to afternoon finishes (53.2 vs 14.8, P = .002) with similar results for starts before 10:30 AM (48.1 vs 14.7, P =.002). There was also a significant correlation between start time and emboli count (P = .02). Of the 55 patients with no postoperative emboli, only 19 had a morning start (relative risk 0.63, P = .011). Patients were 6.9 times more likely to require treatment with Dextran-40 to prevent progression onto a thrombotic stroke if their CEA finished before midday (P = .008).
  
  
  CONCLUSIONS
  There is a significantly increased rate of postoperative embolization for operations begun earlier in the day. Carotid endarterectomies performed in the afternoon may be at less risk of developing postoperative thrombotic stroke.
authors.affiliation: Addenbrooke's Hospital, Cambridge, United Kingdom.
authors.forename: David
authors.initials: D
authors.lastname: Bowden
authors.forename: Natalie
authors.initials: N
authors.lastname: Hayes
authors.forename: Nicholas
authors.initials: N
authors.lastname: London
authors.forename: Peter
authors.initials: P
authors.lastname: Bell
authors.forename: A Ross
authors.initials: AR
authors.lastname: Naylor
authors.forename: Paul
authors.initials: P
authors.lastname: Hayes
mesh_terms: D000368:Aged; D002560:Cerebrovascular Circulation; D002940:Circadian Rhythm; D016894:Endarterectomy, Carotid / Q000009:adverse effects*; D006801:Humans; D020766:Intracranial Embolism / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging; D015539:Platelet Activation / Q000502:physiology; D017585:Ultrasonography, Doppler, Transcranial