title: Regulation of cerebral blood flow in patients with autonomic dysfunction and severe postural hypotension.
abstract: BACKGROUND
  Whether cerebral blood flow (CBF) autoregulation is maintained in autonomic dysfunction has been debated for a long time, and the rather sparse data available are equivocal. The relationship between CBF and mean arterial blood pressure (MABP) was therefore tested in eight patients with symptoms and signs of severe cardiovascular autonomic dysfunction.
  
  
  METHODS
  Eight patients were included, three of whom had Parkinson's disease, three diabetes, one pure autonomic failure and the last one had multiple system atrophy. By the use of two techniques, the arteriovenous oxygen [(a-v)O2] method and xenon-inhalation with single photon emission tomography, 15 measurements (range 10-20) and three to four CBF measurements, respectively, were obtained in each patient. Following CBF measurements during baseline, MABP was raised gradually using intravenous noradrenaline infusion, and then lowered by application of lower body negative pressure. From the (a-v)O2 samples the CBF response to changes in MABP was evaluated using a computer program fitting one or two regression lines through the plot.
  
  
  CONCLUSIONS
  Preserved autoregulation was observed in three patients, while the remaining five patients showed a linear relationship between CBF and MABP. Comparison of the results of the tomographic CBF measurements to the (a-v)O2 data demonstrated that it is not possible to assess whether CBF is autoregulated or not with only three to four pairs of data.
authors.affiliation: Department of Clinical Physiology and Nuclear Medicine, KF 4011, Rigshospitalet, Blegdamsvej 9, DK-2100 Copenhagen, Denmark. bhesse@rh.dk
authors.forename: Birger
authors.initials: B
authors.lastname: Hesse
authors.forename: Jesper
authors.initials: J
authors.lastname: Mehlsen
authors.forename: Finn
authors.initials: F
authors.lastname: Boesen
authors.forename: Jes F
authors.initials: JF
authors.lastname: Schmidt
authors.forename: Erling B
authors.initials: EB
authors.lastname: Andersen
authors.forename: Gunhild
authors.initials: G
authors.lastname: Waldemar
authors.forename: Allan R
authors.initials: AR
authors.lastname: Andersen
authors.forename: Olaf B
authors.initials: OB
authors.lastname: Paulson
authors.forename: Sissel
authors.initials: S
authors.lastname: Vorstrup
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D000368:Aged; D001158:Arteries; D001342:Autonomic Nervous System Diseases / Q000097:blood / Q000150:complications* / Q000000981:diagnostic imaging / Q000503:physiopathology*; D001794:Blood Pressure / Q000187:drug effects; D002560:Cerebrovascular Circulation; D006801:Humans; D007024:Hypotension, Orthostatic / Q000097:blood / Q000150:complications* / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008150:Lower Body Negative Pressure; D009638:Norepinephrine / Q000494:pharmacology; D010100:Oxygen / Q000097:blood; D014055:Tomography, Emission-Computed; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014680:Veins; D014978:Xenon / Q000008:administration & dosage
chemical_list: D014662:Vasoconstrictor Agents; D014978:Xenon; D010100:Oxygen; D009638:Norepinephrine