title: Dynamic cerebral autoregulation in homozygous Sickle cell disease.
abstract: OBJECTIVE
  Sickle cell disease (SCD) is associated with cerebral hyperperfusion and an increased risk of stroke. Also, both recurrent microvascular obstruction and chronic hemolysis affect endothelial function, potentially interfering with systemic and cerebral blood flow control. We addressed the question whether cerebrovascular control in patients with SCD is affected and related to hemolysis.
  
  
  METHODS
  Systemic and cerebrovascular control were studied in 18 patients with SCD and 10 healthy subjects. Dynamic cerebral autoregulation was evaluated by transfer function analysis assessing the relationship between mean cerebral blood flow velocity and mean arterial pressure.
  
  
  RESULTS
  Normal baroreflex sensitivity and postural cardiovascular reflex responses indicated integrity of systemic cardiovascular control. In the low- (0.07 to 0.15 Hz) frequency region, mean arterial pressure variability was comparable for both groups, but a larger mean cerebral blood flow velocity variability in SCD (6.1 [4.6 to 7.0] versus 4.2 [2.6 to 5.2] [cm x s(-1)](2) x Hz(-1); P<0.05) indicated a reduced capacity to buffer the transfer of blood pressure surges to the cerebral tissue. Impairment of dynamic cerebrovascular control was confirmed by a reduced mean arterial pressure-to-mean cerebral blood flow velocity transfer function phase lead in SCD versus healthy subjects (32+/-17 degrees versus 50+/-19 degrees , P<0.05) that was unrelated to the severity of hemolysis.
  
  
  CONCLUSIONS
  In patients with SCD, dynamic cerebral autoregulation is impaired but appears unrelated to hemolysis.
authors.affiliation: Department of Internal Medicine, AMC Center for Heart Failure Research, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Yu-Sok
authors.initials: YS
authors.lastname: Kim
authors.forename: Erfan
authors.initials: E
authors.lastname: Nur
authors.forename: Eduard J
authors.initials: EJ
authors.lastname: van Beers
authors.forename: Jasper
authors.initials: J
authors.lastname: Truijen
authors.forename: Shyrin C A T
authors.initials: SC
authors.lastname: Davis
authors.forename: Bart J
authors.initials: BJ
authors.lastname: Biemond
authors.forename: Johannes J
authors.initials: JJ
authors.lastname: van Lieshout
mesh_terms: D000328:Adult; D000755:Anemia, Sickle Cell / Q000000981:diagnostic imaging / Q000503:physiopathology*; D001772:Blood Cell Count; D001794:Blood Pressure / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology; D006461:Hemolysis / Q000502:physiology; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D008297:Male; D017585:Ultrasonography, Doppler, Transcranial