Regulation of cerebral blood flow in patients with autonomic dysfunction and severe postural hypotension.
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.
Hesse
Birger
B
Department of Clinical Physiology and Nuclear Medicine, KF 4011, Rigshospitalet, Blegdamsvej 9, DK-2100 Copenhagen, Denmark. bhesse@rh.dk
Mehlsen
Jesper
J
Boesen
Finn
F
Schmidt
Jes F
JF
Andersen
Erling B
EB
Waldemar
Gunhild
G
Andersen
Allan R
AR
Paulson
Olaf B
OB
Vorstrup
Sissel
S
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
D014662:Vasoconstrictor Agents; D014978:Xenon; D010100:Oxygen; D009638:Norepinephrine