|Classification and external resources|
Orthostatic hypotension, also known as postural hypotension, orthostasis, and colloquially as head rush or dizzy spell, is a form of hypotension in which a person's blood pressure suddenly falls when standing up or stretching. Medically it is defined as a fall in systolic blood pressure of at least 20mm Hg and diastolic blood pressure of at least 10 mm Hg when a person assumes a standing position.
The symptom is caused by blood pooling in the lower extremities upon a change in body position. It is quite common and can occur briefly in anyone, although it is particularly prevalent among the elderly, and those with low blood pressure.
Signs and symptoms 
When orthostatic hypotension is present, the following symptoms can occur after sudden standing or stretching (after standing):
- Euphoria or dysphoria
- Bodily dissociation
- Distortions in hearing
- Temporary decrease in hearing
- Blurred or dimmed vision (possibly to the point of momentary blindness)
- Generalized (or extremity) numbness/tingling and fainting
- Coat hanger pain (pain centered in the neck and shoulders)
- And in rare, extreme cases, vasovagal syncope (a specific type of fainting).
They are consequences of insufficient blood pressure and cerebral perfusion (blood supply). Occasionally, there may be a feeling of warmth in the head and shoulders for a few seconds after the dizziness subsides. The drop in blood pressure may cause a vasovagal episode to occur.
Orthostatic hypotension is primarily caused 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. 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 hypovolemia, diseases, medications, or, very rarely, safety harnesses.
Orthostatic hypotension may be caused by hypovolemia (a decreased amount of blood in the body), 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.
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. 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 syncope unless the patient has developed true autonomic failure or has an unrelated cardiac 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.
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.
Recently, a common but underdiagnosed condition suspected to be closely related to orthostatic hypotension is spontaneous intracranial hypotension, which results from cerebrospinal fluid leakage. It affects women more than men and peaks at ages between 40 and 50.
A study by a Harvard Medical School team found the two sacs in the inner ear, the utricle and the saccule, affect brain blood flow; thus inner ear problems, which increase with old age, may be involved in orthostatic hypotension.
Orthostatic hypotension can be a side effect of certain antidepressants, such as tricyclics or MAOIs. Marijuana and delta 9-tetrahydrocannabinol can on occasion produce marked orthostatic hypotension. Orthostatic hypotension can also be a side effect of alpha1 adrenergic blocking agents. Alpha1 blockers inhibit vasoconstriction normally initiated by the baroreceptor reflex upon postural change and the subsequent drop in pressure.
The use of a safety harness can also contribute to orthostatic hypotension in the event of a fall. While a harness may safely rescue its user from a fall, the leg loops of a standard safety or climbing harness further restrict return blood flow from the legs to the heart, contributing to the decrease in blood pressure.
Other factors 
Patients who are prone to orthostatic hypotension are the elderly, post partum mothers and those who have 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.
The Orthostatic hypotension is also associated with Naturopathy treatment and during practice of yoga where the pressure gradient varies during these practices.
There is a simple test for OH which measures the person's blood pressure while seated or reclining at rest, and again upon standing up. 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 from supine to standing may indicate a compensatory effort by the heart to maintain cardiac output.
A tilt table test may also be performed.
See also 
- "Orthostatic hypotension" at Dorland's Medical Dictionary
- Lee C, Porter KM (Apr 2007). "Suspension trauma". Emerg Med J. 24 (4): 237–8. doi:10.1136/emj.2007.046391. PMC 2658225. PMID 17384373.
- "Dopamine Beta-Hydroxylase Deficiency". GeneReviews — NCBI Bookshelf.
- "Minute organs in the ear can alter brain blood flow". BBC News. 2009-12-27. Retrieved 2009-12-27.
- 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.
- 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.
- Jones RT. (2002). "Cardiovascular system effects of marijuana". J Clin Pharmacol 42 (11 Suppl): 58S–63S. PMID 12412837.
- Orthostatic Hypotension at Merck Manual of Diagnosis and Therapy Home Edition
- Logan, IC; Witham, MD (2012 Sep). "Efficacy of treatments for orthostatic hypotension: a systematic review.". Age and ageing 41 (5): 587–94. doi:10.1093/ageing/afs061. PMID 22591985.
- 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.
- Bradley JG, Davis KA (Dec 2003). "Orthostatic hypotension". Am Fam Physician. 68 (12): 2393–8. PMID 14705758.
- DYNA Dysautonomia Youth Network of America, Inc.
- Dysautonomia Information Network
- Dysautonomia Support Network
- Drugs that cause Orthostatic hypotension – wrongdiagnosis.com
- Timothy C. Hain, MD. Orthostatic hypotension