Several studies have shown that standing up is a frequent (3–10%) trigger of loss of consciousness both in young and old subjects. An exaggerated transient BP (blood pressure) fall upon standing is the underlying cause. IOH (initial orthostatic hypotension) is defined as a transient BP decrease within 15 s after standing, >40 mmHg SBP (systolic BP) and/or >20 mmHg DBP (diastolic BP) with symptoms of cerebral hypoperfusion. It differs distinctly from typical orthostatic hypotension (i.e. BP decrease >20 mmHg SBP and/or >10 mmHg DBP after 3 min of standing) as the BP decrease is transient. Only continuous beat-to-beat BP measurement during an active standing-up manoeuvre can document this condition. As IOH is only associated with active rising, passive tilting is of no diagnostic value. The pathophysiology of IOH is thought to be a temporal mismatch between cardiac output and vascular resistance. The marked decrease of vascular resistance during rising is similar to that observed at the onset of leg exercise and is absent during head-up tilting. It is attributed to vasodilatation in the working muscle through local mechanisms. Standing up causes an initial increase in venous return through the effects of contraction of leg and abdominal muscles. The consequent sudden increase in right atrial pressure may contribute to the fall in systemic vascular resistance through a reflex effect. This review alerts clinicians and clinician scientists to a common, yet often neglected, condition that occurs only upon an active change of posture and discusses its epidemiology, pathophysiology and management.
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February 2007
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Review Article|
January 03 2007
Initial orthostatic hypotension: review of a forgotten condition
Wouter Wieling;
*Department of Internal Medicine, Academic Medical Center/University of Amsterdam, Amsterdam, The Netherlands
Correspondence: Dr Wouter Wieling (email [email protected]).
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C. T. Paul Krediet;
C. T. Paul Krediet
*Department of Internal Medicine, Academic Medical Center/University of Amsterdam, Amsterdam, The Netherlands
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Nynke van Dijk;
Nynke van Dijk
*Department of Internal Medicine, Academic Medical Center/University of Amsterdam, Amsterdam, The Netherlands
†Clinical Epidemiology and Biostatistics (NvD), Academic Medical Center/University of Amsterdam, Amsterdam, The Netherlands
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Mark Linzer;
Mark Linzer
‡Department of Medicine, University of Wisconsin, Madison, Wisconsin, U.S.A.
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Michael E. Tschakovsky
Michael E. Tschakovsky
§School of Physical and Health Education, Queen's University, Kingston, Ontario, Canada
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Publisher: Portland Press Ltd
Received:
April 21 2006
Revision Received:
May 27 2006
Accepted:
July 13 2006
Accepted Manuscript online:
January 03 2007
Online ISSN: 1470-8736
Print ISSN: 0143-5221
The Biochemical Society
2007
Clin Sci (Lond) (2007) 112 (3): 157–165.
Article history
Received:
April 21 2006
Revision Received:
May 27 2006
Accepted:
July 13 2006
Accepted Manuscript online:
January 03 2007
Citation
Wouter Wieling, C. T. Paul Krediet, Nynke van Dijk, Mark Linzer, Michael E. Tschakovsky; Initial orthostatic hypotension: review of a forgotten condition. Clin Sci (Lond) 1 February 2007; 112 (3): 157–165. doi: https://doi.org/10.1042/CS20060091
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