Orthostatic hypotension
Very mild occasional orthostatic hypotension is common and can occur briefly in anyone, although it is prevalent in particular among the elderly and those with known low blood pressure.
[6] The numerous possible causes for orthostatic hypotension include certain medications (e.g. alpha blockers), autonomic neuropathy, decreased blood volume, multiple system atrophy, and age-related blood-vessel stiffness.
Baroreceptors, a kind of mechanoreceptors, play a crucial role in conveying data about blood pressure in the autonomic nervous system.
The data is conveyed to regulate the peripheral resistance and heart output, keeping blood pressure within an established normal limit.
[7] Arterial baroreceptors detect changes in blood pressure and transmit this information to the brainstem, the nucleus of the solitary tract, which modulates the activity of the autonomic nervous system (ANS).
[8] What's more, the venoarteriolar axon reflex, which results in the constriction of arterial flow to muscles, skin, and adipose tissue also helps stabilize blood pressure.
Some also report difficulty concentrating, blurred vision, tremulousness, vertigo, anxiety, palpitations (awareness of the heartbeat), unsteadiness, feeling sweaty or clammy, and sometimes nausea.
It is also present in many patients with Parkinson's disease or Lewy body dementias resulting from sympathetic denervation of the heart or as a side effect of dopaminomimetic therapy.
This rarely leads to fainting unless the person has developed true autonomic failure or has an unrelated heart problem.
Alpha1 blockers inhibit vasoconstriction normally initiated by the baroreceptor reflex upon postural change and the subsequent drop in pressure.
[27] Patients prone to orthostatic hypotension are the elderly, post partum mothers, and those having been on bed rest.
[citation needed] Normally, a series of cardiac, vascular, neurologic, muscular, and neurohumoral responses occurs quickly so the blood pressure does not fall very much.
[33] Delayed orthostatic hypotension is frequently characterized by a sustained systolic blood pressure decrease of ≥20 mm Hg or a sustained diastolic blood pressure decrease ≥of 10 mm Hg beyond 3 minutes of standing or upright tilt table testing.
[33] Various measures can be used to improve the return of blood to the heart; the wearing of compression stockings and exercises ("physical counterpressure maneuvers" or PCMs) can be undertaken just before standing up (e.g., leg crossing and squatting), as muscular contraction helps return blood from the legs to the upper body.
[33] The medication midodrine, an α1-adrenergic receptor agonist, can benefit people with orthostatic hypotension,[33][35] The main side effect is piloerection ("goose bumps").
[37] A number of other measures have slight evidence to support their use – indomethacin, fluoxetine, dopamine antagonists, metoclopramide, domperidone, monoamine oxidase inhibitors with tyramine (can produce severe hypertension), oxilofrine, potassium chloride, and yohimbine.
[42][27] Also, observational data suggest that orthostatic hypotension in middle age increases the risk of eventual dementia and reduced cognitive function.
