NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Autoregulation of cerebral blood flow in orthostatic hypotensionBACKGROUND AND PURPOSE: We sought to evaluate cerebral autoregulation in patients with orthostatic hypotension (OH). METHODS: We studied 21 patients (aged 52 to 78 years) with neurogenic OH during 80 degrees head-up tilt. Blood flow velocities (BFV) from the middle cerebral artery were continuously monitored with transcranial Doppler sonography, as were heart rate, blood pressure (BP), cardiac output, stroke volume, CO2, total peripheral resistance, and cerebrovascular resistance. RESULTS: All OH patients had lower BP (P<.0001), BFV_diastolic (P<.05), CVR (P<.007), and TPR (P<.02) during head-up tilt than control subjects. In control subjects, no correlations between BFV and BP were found during head-up tilt, suggesting normal autoregulation. OH patients could be separated into those with normal or expanded autoregulation (OH_NA; n=16) and those with autoregulatory failure (OH_AF; n=5). The OH_NA group showed either no correlation between BFV and BP (n=8) or had a positive BFV/BP correlation (R2>.75) but with a flat slope. An expansion of the "autoregulated" range was seen in some patients. The OH_AF group was characterized by a profound fall in BFV in response to a small reduction in BP (mean deltaBP <40 mm Hg; R2>.75). CONCLUSIONS: The most common patterns of cerebral response to OH are autoregulatory failure with a flat flow-pressure relationship or intact autoregulation with an expanded autoregulated range. The least common pattern is autoregulatory failure with a steep flow-pressure relationship. Patients with patterns 1 and 2 have an enhanced capacity to cope with OH, while those with pattern 3 have reduced capacity.
Document ID
20040172807
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Novak, V.
(Mayo Clinic and Foundation Rochester, Minn. 55905, United States)
Novak, P.
Spies, J. M.
Low, P. A.
Date Acquired
August 22, 2013
Publication Date
January 1, 1998
Publication Information
Publication: Stroke; a journal of cerebral circulation
Volume: 29
Issue: 1
ISSN: 0039-2499
Subject Category
Aerospace Medicine
Funding Number(s)
CONTRACT_GRANT: PO1 NS32352
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Cardiopulmonary

Available Downloads

There are no available downloads for this record.
No Preview Available