orthostatic syncope

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Orthostatic hypotension (OH) or postural hypotension

  • occurs when mechanisms for the regulation of orthostatic BP control fails. Such regulation depends on the baroreflexes, normal blood volume, and defenses against excessive venous pooling.

OH is defined as a reduction of systolic BP of at least 20 mm Hg or diastolic blood pressure of at least 10 mm Hg within 3 minutes of standing up (3)

"Classic" postural hypotension occurs within three minutes of standing, "delayed" postural hypotension occurs after three minutes

Orthostatic hypotension (OH) occurs when mechanisms for the regulation of orthostatic BP control fail

  • such regulation depends on the baroreflexes, normal blood volume, and defenses against excessive venous pooling
  • there are many causes of OH
    • aging coupled with diseases such as diabetes and Parkinson's disease results in a prevalence of 10-30% in the elderly (1)
      • these conditions cause baroreflex failure with resulting combination of OH, supine hypertension, and loss of diurnal variation of BP
    • 20% of community-dwelling adults over 60 years old and one in four people in long term residential care have postural hypotension (2)
    • about a quarter of patients with diabetes have postural hypotension (2)
      • High HbA1c, hypertension, and diabetic neuropathy increase its likelihood
    • third of patients with Parkinson's disease have postural hypotension (2)

OH is associated with increased risk of (2):

  • falls
  • heart failure
  • coronary heart disease
  • stroke
  • atrial fibrillation
  • all-cause mortality
  • increased risk of cognitive impairment, dementia, and depression

Postural hypotension should be investigated, especially if the patient is symptomatic.

Usually the patient will complain of blackouts and dizzy turns, the result of impaired cerebral perfusion.

Treatment of OH

  • is imperfect since it is impossible to normalize standing BP without generating excessive supine hypertension
  • practical goal is to improve standing BP so as to minimize symptoms and to improve standing time in order to be able to undertake orthostatic activities of daily living, without excessive supine hypertension.
  • possible to achieve these goals with a combination of fludrocortisone, a pressor agent (midodrine or droxidopa), supplemented with procedures to improve orthostatic defenses during periods of increased orthostatic stress. Such procedures include water bolus treatment and physical countermaneuvers

Notes (4):

  • a systematic review (13 studies; n=513) concludes evidence about effects of fludrocortisone on blood pressure, orthostatic symptoms or adverse events in those with orthostatic hypotension and diabetes or Parkinson's is very uncertain, with lack of data on long-term treatment in other diseases

Reference:

  • Low VA, Tomalia TA. Orthostatic Hypotension: Mechanisms, Causes, Management.J Clin Neurol. 2015 Jul; 11(3): 220-226.
  • Gilani A et al. Postural Hypotension. BMJ 2021;373:n922 http://dx.doi.org/10.1136/bmj.n922
  • The Consensus Committee of the American Autonomic Society and the American Academy of Neurology. Consensus statement on the definition of orthostatic hypotension, pure autonomic failure, and multiple system atrophy. Neurology. 1996;46:1470.
  • Veazie S, Peterson K, Ansari Y, Chung KA, Gibbons CH., Raj SR, Helfand M. Fludrocortisone for orthostatic hypotension. Cochrane Database of Systematic Reviews 2021, Issue 5. Art. No.: CD012868. DOI: 10.1002/14651858.CD012868.pub2. Accessed 09 December 2021.

Last edited 12/2021 and last reviewed 04/2022

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