Is there diurnal variation in initial and delayed orthostatic hypotension during standing and head-up tilt?

Hdl Handle:
http://hdl.handle.net/10149/218096
Title:
Is there diurnal variation in initial and delayed orthostatic hypotension during standing and head-up tilt?
Authors:
Lewis, N. C. S. (Nia); Atkinson, G. (Greg); Lucas, S. J. E.; Grant, E. J. M.; Jones, H. (Helen); Tzeng, Y-C. (YuChieh); Horsman, H.; Ainslie, P. N. (Philip)
Affiliation:
Liverpool John Moores University, Research Institute for Sport and Exercise Sciences.
Citation:
Lewis, N.C., Atkinson, G., Lucas, S.J., Grant, E.J., Jones, H., Tzeng, Y.C., Horsman, H., Ainslie, P. N. (2011) 'Is there diurnal variation in initial and delayed orthostatic hypotension during standing and head-up tilt?', Chronobiology International, 28 (2), pp.135-45.
Publisher:
Informa Healthcare
Journal:
Chronobiology international
Issue Date:
Mar-2011
URI:
http://hdl.handle.net/10149/218096
DOI:
10.3109/07420528.2010.536283
PubMed ID:
21231875
Abstract:
Moving rapidly from a supine to a standing posture is a common daily activity, yet a significant physiological challenge. Syncope can result from the development of initial orthostatic hypotension (IOH) involving a transient fall in systolic/diastolic blood pressure (BP) of >40/20 mm Hg within the first 15 s, and/or a delayed orthostatic hypotension (DOH) involving a fall in systolic/diastolic BP of >20/10 mm Hg within 15 min of posture change. Although epidemiological data indicate a heightened syncope risk in the morning, little is known about the diurnal variation in the IOH and DOH mechanisms associated with postural change. The authors hypothesized that the onset of IOH and DOH occurs sooner, and the associated cardiorespiratory and cerebrovascular changes are more pronounced, in the early morning. At 06:00 and 16:00 h, 17 normotensive volunteers, aged 26 ± 1 yrs (mean ± SE), completed a protocol involving supine rest, an upright stand, and a 60° head-up tilt (HUT) during which continuous beat-to-beat measurements of middle cerebral artery velocity (MCAv), mean arterial BP (MAP), heart rate, and end-tidal Pco(2) (P(ET)co(2)) were obtained. Mean MCAv was ∼12% lower at baseline in the morning (p ≤ .01) and during the HUT (p < .01), despite a morning elevation in P(ET)co(2) by ∼2.2 mm Hg (p = .01). The decline in MAP during initial standing (morning vs. afternoon: 50% ± 4% vs. 49% ± 3%) and HUT (39% ± 3% vs. 38% ± 3%) did not vary with time-of-day (p > .30). In conclusion, although there is a marked reduction in MCAv in the morning, there is an absence of diurnal variation in the onset of and associated physiological responses associated with IOH and DOH. These responses, at least in this population, are unlikely contributors to the diurnal variation in orthostatic tolerance.
Type:
Article
Language:
en
Keywords:
blood flow velocity; blood pressure; cerebrovascular circulation; circadian rhythm; hypotension; middle cerebral artery; posture; syncope; tilt-table test; ultrasonography; orthostatic tolerance
ISSN:
1525-6073
Rights:
Subject to restrictions, author can archive post-print (ie final draft post-refereeing). For full details see http://www.sherpa.ac.uk/romeo/ [Accessed 10/04/2012].
Citation Count:
0 [Scopus, 10/04/2012]

Full metadata record

DC FieldValue Language
dc.contributor.authorLewis, N. C. S. (Nia)en_GB
dc.contributor.authorAtkinson, G. (Greg)en_GB
dc.contributor.authorLucas, S. J. E.en_GB
dc.contributor.authorGrant, E. J. M.en_GB
dc.contributor.authorJones, H. (Helen)en_GB
dc.contributor.authorTzeng, Y-C. (YuChieh)en_GB
dc.contributor.authorHorsman, H.en_GB
dc.contributor.authorAinslie, P. N. (Philip)en_GB
dc.date.accessioned2012-04-10T16:05:03Z-
dc.date.available2012-04-10T16:05:03Z-
dc.date.issued2011-03-
dc.identifier.citationChronobiology International; 28 (2):135-45en_GB
dc.identifier.issn1525-6073-
dc.identifier.pmid21231875-
dc.identifier.doi10.3109/07420528.2010.536283-
dc.identifier.urihttp://hdl.handle.net/10149/218096-
dc.description.abstractMoving rapidly from a supine to a standing posture is a common daily activity, yet a significant physiological challenge. Syncope can result from the development of initial orthostatic hypotension (IOH) involving a transient fall in systolic/diastolic blood pressure (BP) of >40/20 mm Hg within the first 15 s, and/or a delayed orthostatic hypotension (DOH) involving a fall in systolic/diastolic BP of >20/10 mm Hg within 15 min of posture change. Although epidemiological data indicate a heightened syncope risk in the morning, little is known about the diurnal variation in the IOH and DOH mechanisms associated with postural change. The authors hypothesized that the onset of IOH and DOH occurs sooner, and the associated cardiorespiratory and cerebrovascular changes are more pronounced, in the early morning. At 06:00 and 16:00 h, 17 normotensive volunteers, aged 26 ± 1 yrs (mean ± SE), completed a protocol involving supine rest, an upright stand, and a 60° head-up tilt (HUT) during which continuous beat-to-beat measurements of middle cerebral artery velocity (MCAv), mean arterial BP (MAP), heart rate, and end-tidal Pco(2) (P(ET)co(2)) were obtained. Mean MCAv was ∼12% lower at baseline in the morning (p ≤ .01) and during the HUT (p < .01), despite a morning elevation in P(ET)co(2) by ∼2.2 mm Hg (p = .01). The decline in MAP during initial standing (morning vs. afternoon: 50% ± 4% vs. 49% ± 3%) and HUT (39% ± 3% vs. 38% ± 3%) did not vary with time-of-day (p > .30). In conclusion, although there is a marked reduction in MCAv in the morning, there is an absence of diurnal variation in the onset of and associated physiological responses associated with IOH and DOH. These responses, at least in this population, are unlikely contributors to the diurnal variation in orthostatic tolerance.en_GB
dc.language.isoenen
dc.publisherInforma Healthcareen_GB
dc.rightsSubject to restrictions, author can archive post-print (ie final draft post-refereeing). For full details see http://www.sherpa.ac.uk/romeo/ [Accessed 10/04/2012].en_GB
dc.subjectblood flow velocityen_GB
dc.subjectblood pressureen_GB
dc.subjectcerebrovascular circulationen_GB
dc.subjectcircadian rhythmen_GB
dc.subjecthypotensionen_GB
dc.subjectmiddle cerebral arteryen_GB
dc.subjectpostureen_GB
dc.subjectsyncopeen_GB
dc.subjecttilt-table testen_GB
dc.subjectultrasonographyen_GB
dc.subjectorthostatic toleranceen_GB
dc.titleIs there diurnal variation in initial and delayed orthostatic hypotension during standing and head-up tilt?en
dc.typeArticleen
dc.contributor.departmentLiverpool John Moores University, Research Institute for Sport and Exercise Sciences.en_GB
dc.identifier.journalChronobiology internationalen_GB
ref.citationcount0 [Scopus, 10/04/2012]en_GB
or.citation.harvardLewis, N.C., Atkinson, G., Lucas, S.J., Grant, E.J., Jones, H., Tzeng, Y.C., Horsman, H., Ainslie, P. N. (2011) 'Is there diurnal variation in initial and delayed orthostatic hypotension during standing and head-up tilt?', Chronobiology International, 28 (2), pp.135-45.en_GB

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