title: Transcranial Doppler monitoring with head-upright tilting in patients with syncope.
abstract: BACKGROUND
  The aim of our study was to evaluate the effects of orthostatic stress produced by the head-upright tilt test on human cerebral hemodynamics by transcranial Doppler sonography.
  
  
  METHODS
  We studied 60 subjects who were divided into two groups; one of normal controls (n = 43) and one of patients suffering from syncope (n = 17). A 30-minute head-upright tilt test was conducted on all subjects, and heart rate and blood pressure were monitored by surface electrocardiography and cuff sphygmomanometry, respectively. Cerebral blood flow velocity and cerebral vasoreactivity were continuously monitored using transcranial Doppler sonography.
  
  
  RESULTS
  The maximal decreases in mean blood pressure of controls and patients with syncope were 2.6 +/- 7.8% and 0.5 +/- 7.9% of baseline, respectively. The maximal decreases in mean blood flow velocity in the middle cerebral artery between the two groups reached 19.6 +/- 6.2% and 30.7 +/- 14.1% of baseline, respectively (p < 0.05). The increases in pulsatility index between the two groups were 15.4 +/- 14.3% and 16.9 +/- 21.1% of baseline, respectively.
  
  
  CONCLUSIONS
  The responses of cerebral blood flow to upright tilting differed significantly between normal controls and patients with syncope, implying that the latter may suffer an impairment of cerebral autoregulation. Further studies are needed to ascertain what clinical implications this finding might have.
authors.affiliation: Neurological Institute, Veterans General Hospital-Taipei, Taiwan, ROC.
authors.forename: L C
authors.initials: LC
authors.lastname: Hsu
authors.forename: C M
authors.initials: CM
authors.lastname: Chern
authors.forename: W Y
authors.initials: WY
authors.lastname: Sheng
authors.forename: W J
authors.initials: WJ
authors.lastname: Wong
authors.forename: Y O
authors.initials: YO
authors.lastname: Luk
authors.forename: H H
authors.initials: HH
authors.lastname: Hu
mesh_terms: D000328:Adult; D000368:Aged; D001783:Blood Flow Velocity; D002536:Cerebral Arteries / Q000503:physiopathology; D002560:Cerebrovascular Circulation; D005260:Female; D006706:Homeostasis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011187:Posture; D013575:Syncope / Q000503:physiopathology*; D017585:Ultrasonography, Doppler, Transcranial