title: Stratification of intraoperative ischemic impact by somatosensory evoked potential monitoring, diffusion-weighted imaging and magnetic resonance angiography in carotid endarterectomy with routine shunt use.
abstract: BACKGROUND
  Routine shunting to minimize ischemia during carotid endarterectomy (CEA) is controversial. The aim of this study was to stratify the ischemic parameters associated with CEA and evaluate the effect of routine shunting in attempting to mitigate those ischemia.
  
  
  METHODS
  Data from 248 CEAs with routine shunting were retrospectively evaluated. Our assessment included somatosensory evoked potential (SSEP) amplitude reduction more than 50 % and longer than 5 min (SSEP<50%, >5 min), new postoperative diffusion-weighted imaging lesions (new DWI lesions), and severe stenosis as indicated by reduced ipsilateral middle cerebral artery (MCA) signal on preoperative magnetic resonance angiography (MRA asymmetry), as surrogates of hypoperfusion, microembli, and hemodynamic impairment, respectively.
  
  
  RESULTS
  SSEP<50%, >5 min occurred in 15 % of CEAs during cross-clamping, and shunting reversed the SSEP changes. New DWI lesions were observed in 4.1 %. Pre-clamping the common and external carotid artery during dissection (pre-clamp method) decreased the rate of new DWI lesions compared to without pre-clamping (3.5 % vs. 7.5 %, P = 0.22). Occlusion time was significantly longer in the pre-clamp method than without pre-clamping (P < 0.0001). However, the incidence of SSEP<50%, >5 min was not increased with the pre-clamp method (p = 1.0) when using information regarding SSEP and collaterals to modify the speed of shunt manipulation. MRA asymmetry was identified in 39 CEAs (15.8 %) with correction of asymmetry postoperatively. MRA asymmetry correlated with symptomatic hyperperfusion (P = 0.0034). Only three CEAs had symptomatic hyperperfusion (1.2 %) with minimal symptoms. Ten CEAs sustained transient ischemia, symptomatic hyperperfusion, or 30-day-stroke (composite postoperative ischemic symptoms). Logistic regression analysis confirmed that SSEP<50%, >5 min (p = 0.009), new DWI lesions (p = 0.004) and MRA asymmetry (p = 0.042) were independent predictors of　composite postoperative ischemic symptoms.
  
  
  CONCLUSIONS
  SSEP<50%, >5 min, new DWI lesions, and MRA asymmetry were able to stratify the ischemic impacts in CEA. Meticulous routine shunting could mitigate those appropriately.
authors.affiliation: Department of Neurosurgery, Fuji Brain Institute and Hospital, 270-12 Sugita, Fujinomiya-shi, Shizuoka, 418-0021, Japan, t.inoue-fujinsu@beige.plala.or.jp.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Inoue
authors.forename: Kazuo
authors.initials: K
authors.lastname: Tsutsumi
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Ohwaki
authors.forename: Akira
authors.initials: A
authors.lastname: Tamura
authors.forename: Hideaki
authors.initials: H
authors.lastname: Ono
authors.forename: Isamu
authors.initials: I
authors.lastname: Saito
authors.forename: Nobuhito
authors.initials: N
authors.lastname: Saito
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002545:Brain Ischemia / Q000473:pathology / Q000601:surgery*; D016893:Carotid Stenosis / Q000175:diagnosis / Q000601:surgery; D002560:Cerebrovascular Circulation / Q000502:physiology; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D016894:Endarterectomy, Carotid / Q000379:methods; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D018810:Magnetic Resonance Angiography / Q000379:methods; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000473:pathology / Q000601:surgery; D016343:Monitoring, Intraoperative / Q000379:methods; D012189:Retrospective Studies; D020521:Stroke / Q000601:surgery