title: Cerebral autoregulation in carotid artery occlusive disease assessed from spontaneous blood pressure fluctuations by the correlation coefficient index.
abstract: OBJECTIVE
  Estimation of dynamic cerebral autoregulation from spontaneous fluctuations of arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV) is an attractive monitoring option for cerebral hemodynamic impairment. We evaluated the correlation coefficient index method in patients with severe obstructive carotid disease and compared it with transfer function analysis (frequency domain approach to cerebral autoregulation) and CO2 vasomotor reactivity.
  
  
  METHODS
  In 139 patients with severe unilateral carotid stenosis (>or=70%) or occlusion, CBFV (transcranial Doppler) and ABP (Finapres method) were recorded over 10 minutes. Correlations between systolic pressure, diastolic pressure, and mean ABP and CBFV oscillations over 1-minute epochs were averaged over 10 minutes to form the correlation coefficient indexes (Sx, Dx, Mx, respectively). Transfer function parameters (phase shift and gain between ABP and CBFV oscillations) were determined from the entire 10-minute period. CO2 reactivity was assessed by inhalation of 7% CO2.
  
  
  RESULTS
  The correlation indexes Dx and Mx were significantly higher ipsilateral to stenosis and increased with degree of stenosis, indicating increasing dependence of CBFV on ABP and thus impairment of cerebral autoregulation. Dx and Mx correlated moderately but highly significantly with transfer function parameters and CO2 reactivity and showed a good level of agreement in detecting pathological values. Patients with a small variance of the 1-minute source correlations of Dx and Mx showed clearly better correlation values. Transfer function parameters and CO2 reactivity but not Dx and Mx were significantly poorer in patients with symptomatic stenosis or occlusion.
  
  
  CONCLUSIONS
  The potential of the correlation coefficient indexes Dx and Mx in detecting hemodynamic impairment in patients with carotid stenosis is comparable to that of transfer function analysis and CO2 reactivity testing. In future, a combination of various hemodynamic tests might help to identify patients at risk for ischemic events.
authors.affiliation: Department of Neurology and Clinical Neurophysiology, University of Freiburg, Freiburg, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Reinhard
authors.forename: M
authors.initials: M
authors.lastname: Roth
authors.forename: T
authors.initials: T
authors.lastname: Müller
authors.forename: M
authors.initials: M
authors.lastname: Czosnyka
authors.forename: J
authors.initials: J
authors.lastname: Timmer
authors.forename: A
authors.initials: A
authors.lastname: Hetzel
mesh_terms: D000368:Aged; D001683:Biological Clocks / Q000187:drug effects; D001783:Blood Flow Velocity; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002245:Carbon Dioxide; D002343:Carotid Artery, Internal / Q000503:physiopathology; D016893:Carotid Stenosis / Q000175:diagnosis* / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000502:physiology; D003971:Diastole; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D008297:Male; D011237:Predictive Value of Tests; D012720:Severity of Illness Index; D013223:Statistics as Topic / Q000379:methods; D013599:Systole; D014666:Vasomotor System / Q000187:drug effects / Q000503:physiopathology
chemical_list: D002245:Carbon Dioxide