Orthostatic hypotension

For the television science series, see Head Rush (TV series).
Orthostatic hypotension
Synonyms orthostasis, postural hypotension
Pronunciation /ˌɔːrθəˈstætɪkˌhaɪpəˈtɛnʃən/
Classification and external resources
Specialty Cardiology
ICD-10 I95.1
ICD-9-CM 458.0
DiseasesDB 10470
MeSH D007024

Orthostatic hypotension, also known as postural hypotension[1] or shortened to orthostasis and colloquially called head rush, occurs when a person's blood pressure falls when suddenly standing up from a lying or sitting position. It is defined as a fall in systolic blood pressure of at least 20 mm Hg or diastolic blood pressure of at least 10 mm Hg when a person assumes a standing position. It occurs predominantly by delayed constriction of the lower body blood vessels, which is normally required to maintain an adequate blood pressure when changing position to standing. As a result, blood pools in the blood vessels of the legs for a longer period, and less is returned to the heart, thereby leading to a reduced cardiac output. Mild 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. Severe drops in blood pressure can lead to fainting with a possibility of injury.

There are numerous possible causes for orthostatic hypotension, such as certain medications (e.g. alpha blockers), autonomic neuropathy, decreased blood volume, and age-related blood vessel stiffness.

Apart from addressing the underlying cause, orthostatic hypotension may be treated with a recommendation to increase salt and water intake (to increase the blood volume), wearing compression stockings, and sometimes medication (fludrocortisone, midodrine or others).

Signs and symptoms

Orthostatic hypotension is characterised by symptoms that occur after standing (from lying or sitting), particularly when this is done rapidly. Many report lightheadedness (a feeling that one might be about to faint), sometimes severe. Generalized weakness or tiredness may also occur. Some also report difficulty concentrating, blurred vision, tremulousness, vertigo, anxiety, palpitations (awareness of the heartbeat), feeling sweaty or clammy, and sometimes nausea. A person may look pale.[2]

Causes

Orthostatic hypotension is caused primarily by gravity-induced blood-pooling in the lower extremities, which in turn compromises venous return, resulting in decreased cardiac output and subsequent lowering of arterial pressure. For example, changing from a lying position to standing loses about 700 ml of blood from the thorax, with a decrease in systolic and diastolic blood pressures.[3] The overall effect is an insufficient blood perfusion in the upper part of the body.

Still, the blood pressure does not normally fall very much, because it immediately triggers a vasoconstriction (baroreceptor reflex), pressing the blood up into the body again. (Often, this mechanism is exaggerated and is why diastolic blood pressure is a bit higher when a person is standing up, compared to a person in horizontal position.) Therefore, a secondary factor that causes a greater than normal fall in blood pressure is often required. Such factors include low blood volume, diseases, and medications.

Hypovolemia

Orthostatic hypotension may be caused by low blood volume, resulting from bleeding, the excessive use of diuretics, vasodilators, or other types of drugs, dehydration, or prolonged bed rest. It also occurs in people with anemia.

Diseases

The disorder may be associated with Addison's disease, atherosclerosis (build-up of fatty deposits in the arteries), diabetes, pheochromocytoma, and certain neurological disorders, including multiple system atrophy and other forms of dysautonomia. It is also associated with Ehlers-Danlos syndrome and anorexia nervosa. It is also present in many patients with Parkinson's disease 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.

Another disease, dopamine beta hydroxylase deficiency, also thought to be underdiagnosed, causes loss of sympathetic noradrenergic function and is characterized by a low or extremely low levels of norepinephrine, but an excess of dopamine.[4]

Quadriplegics and paraplegics also might experience these symptoms due to multiple systems' inability to maintain a normal blood pressure and blood flow to the upper part of the body.

Medication

Orthostatic hypotension can be a side-effect of certain antidepressants, such as tricyclics[5] or monoamine oxidase inhibitors (MAOIs).[6] Marijuana and tetrahydrocannabinol can on occasion produce marked orthostatic hypotension.[7] Orthostatic hypotension can also be a side effect of Alpha-1 blockers (alpha1 adrenergic blocking agents). Alpha1 blockers inhibit vasoconstriction normally initiated by the baroreceptor reflex upon postural change and the subsequent drop in pressure.[8]

Other factors

Patients prone to orthostatic hypotension are the elderly, post partum mothers, and those having been on bedrest. People suffering from anorexia nervosa and bulimia nervosa often suffer from orthostatic hypotension as a common side-effect. Consuming alcohol may also lead to orthostatic hypotension due to its dehydrating effects.

Diagnosis

Orthostatic hypotension can be confirmed by measuring a person's blood pressure after lying flat for 5 minutes, then 1 minute after standing, and 3 minutes after standing.[9] Orthostatic hypotension is defined as a fall in systolic blood pressure of at least 20 mmHg and/or in the diastolic blood pressure of at least 10 mmHg between the supine reading and the upright reading. In addition, the heart rate should also be measured for both positions. A significant increase in heart rate from supine to standing may indicate a compensatory effort by the heart to maintain cardiac output or postural orthostatic tachycardia syndrome (POTS). A tilt table test may also be performed.

Management

Apart from treating underlying reversible causes (e.g. stopping or reducing certain medications) there are a number of measures that can improve the symptoms of orthostatic hypotension and prevent episodes of syncope. Even small increases in the blood pressure may be sufficient to maintain blood flow to the brain on standing.[10] In people who do not have a diagnosis of high blood pressure, drinking 2-3 liters of fluid a day and taking 10 grams of salt can improve symptoms; keeping the head of the bed slightly elevated reduces the return of this fluid to the kidneys at night and causing nighttime urine production and blood pressure increases.[10] Various measures can be used to improve the return of blood to the heart: the wearing of compression stockings and exercises ("physical counterpressure manoeuvres" or PCMs) that can be undertaken just before standing up (such as leg crossing and squatting).[10] The medication midodrine can benefit people with orthostatic hypotension,[10][11] The main side-effect is piloerection ("goose bumps").[11] Fludrocortisone is also used, although based on more limited evidence.[10]

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.[12]

Prognosis

Orthostatic hypotension may cause accidental falls.[13] It is also linked to an increased risk of cardiovascular disease, heart failure, and stroke.[14]

See also

References

  1. ↑ "Orthostatic hypotension" at Dorland's Medical Dictionary
  2. ↑ Kasper DL, Fauci AS, Hauser SL, Longo DL, James JL, Loscalzo J (2015). Harrison's principles of internal medicine. 2 (19th ed.). New York: McGraw-Hill Medical Publishing Division. p. 2639. ISBN 978-0-07-180215-4.
  3. ↑ Idiopathic Orthostatic Hypotension and other Autonomic Failure Syndromes at eMedicine
  4. ↑ "Dopamine Beta-Hydroxylase Deficiency". GeneReviews — NCBI Bookshelf.
  5. ↑ Jiang W, Davidson JR (2005). "Antidepressant therapy in patients with ischemic heart disease". Am Heart J. 150 (5): 871–81. doi:10.1016/j.ahj.2005.01.041. PMID 16290952.
  6. ↑ Delini-Stula A, Baier D, Kohnen R, Laux G, Philipp M, Scholz HJ (1999). "Undesirable blood pressure changes under naturalistic treatment with moclobemide, a reversible MAO-A inhibitor—results of the drug utilization observation studies". Pharmacopsychiatry. 32 (2): 61–7. doi:10.1055/s-2007-979193. PMID 10333164.
  7. ↑ Jones RT. (2002). "Cardiovascular system effects of marijuana". J Clin Pharmacol. 42 (11 Suppl): 58S–63S. doi:10.1002/j.1552-4604.2002.tb06004.x. PMID 12412837.
  8. ↑ Orthostatic Hypotension at Merck Manual of Diagnosis and Therapy Home Edition
  9. ↑ "STEADI - Measuring Orthostatic Blood Pressure" (PDF). Centers for Disease Control and Prevention. Retrieved 20 December 2014.
  10. 1 2 3 4 5 Moya, A.; Sutton, R.; Ammirati, F.; et al. (27 August 2009). "Guidelines for the diagnosis and management of syncope (version 2009): The Task Force for the Diagnosis and Management of Syncope of the European Society of Cardiology (ESC)". European Heart Journal. 30 (21): 2631–2671. doi:10.1093/eurheartj/ehp298. PMC 3295536Freely accessible. PMID 19713422.
  11. 1 2 Izcovich, A.; Gonzalez Malla, C.; Manzotti, M.; Catalano, H. N.; Guyatt, G. (22 August 2014). "Midodrine for orthostatic hypotension and recurrent reflex syncope: A systematic review". Neurology. 83 (13): 1170–1177. doi:10.1212/WNL.0000000000000815. PMID 25150287.
  12. ↑ Logan, IC; Witham, MD (September 2012). "Efficacy of treatments for orthostatic hypotension: a systematic review.". Age and ageing. 41 (5): 587–94. doi:10.1093/ageing/afs061. PMID 22591985.
  13. ↑ Romero-Ortuno R, Cogan L, Foran T, Kenny RA, Fan CW (2011). "Continuous noninvasive orthostatic blood pressure measurements and their relationship with orthostatic intolerance, falls, and frailty in older people". J Am Geriatr Soc. 59 (4): 655–65. doi:10.1111/j.1532-5415.2011.03352.x. PMID 21438868.
  14. ↑ Ricci, F; Fedorowski, A; Radico, F; Romanello, M; Tatasciore, A; Di Nicola, M; Zimarino, M; De Caterina, R (1 July 2015). "Cardiovascular morbidity and mortality related to orthostatic hypotension: a meta-analysis of prospective observational studies.". European Heart Journal. 36 (25): 1609–17. doi:10.1093/eurheartj/ehv093. PMID 25852216.
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