Orthostatic hypotension

Assistant Editor-in-Chief: Somal Khan, M.D.

Overview
Orthostatic hypotension (also known as postural hypotension, orthostatic intolerance and, colloquially, as head rush or a dizzy spell) is a sudden fall in blood pressure, typically greater than 20/10 mm Hg, that occurs when a person assumes a more vertical postion i.e from sitting to standing or from lying down to sitting or standing, usually after a prolonged period of rest.

Symptoms
Symptoms, which generally occur after sudden standing, include dizziness, lightheadedness, headache, blurred or dimmed vision (possibly to the point of momentary blindness), and fainting. They are consequences of insufficient blood pressure and cerebral perfusion (blood supply).

Causes
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 subsequently lowering of arterial pressure. For example, if a person changes from a lying position to standing, he or she will lose about 700 ml of blood from the thorax. It can also be noted that although there is a decreased systolic (contracting) blood pressure, there is actually an increased diastolic (resting) blood pressure. However, 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, pressing the blood up into the body again. Therefore, a secondary factor is required that, in turn, cause a fall in blood pressure greater than normal. Such factors include hypovolemia, associated disease states, pharmacotherapy, or, very rarely, safety harnesses.

Hypovolemia
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 ,pregnancy in females and venous varicosities .Certain  circulating endogenous vasodilators which causes hyperbardykinism and mastocytosis may also cause postural hypotension.

Diseases
The disorder may be associated with Addison's disease, atherosclerosis (build-up of fatty deposits in the arteries), amyloidosis, alcohol neuropathy,  spinal cord disease, multiple sclerosis, multiple cerebral infarcts, Tabes Dorsalis, Syringomyelia, idiopathic orthostatic hypotension,  diabetes, carcinoid syndrome, pheochromocytoma, and certain neurological disorders including Shy-Drager syndrome 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.

Medication
Orthostatic hypotension can result from antihypertensive medicines such as diuretics especially furosemide,Beta Blockers, Calcium channel blockers and ACE Inhibitors,Prazosin and Tamsulosin which is a drug for treatment of Benign Prostatic Hyperplasia. Nitrates have shown to cause side effects of postural hypotension. It can also be the side effect of certain anti-psychotics such as zotepine, neuroleptics ,sedative hypnotics and anti-depressants, such as tricyclics or MAOIs. It is also a side effect of the short-term use of marijuana.

Harnesses
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 risk factors
Patients who are prone to orthostatic hypotension are the elderly, postpartum mothers, and those who have been on bedrest.

Treatment and management
There are medications to treat hypotension. In addition, there are many lifestyle advices. Many of them, however, are specific for a certain cause of orthostatic hypotension.

Medical management
Some drugs that are used in the treatment of orthostatic hypotension include fludrocortisone (Florinef), erythropoietin and midodrine. Pyridostigmine bromide (Mestinon) is now also used to treat orthostatic hypotension.

Lifestyle advice
Some suggestions for minimizing the effects include:


 * Checking blood pressure regularly with a home monitoring kit. Check when lying flat and when standing as well as when symptoms occur.
 * Standing slowly rather than quickly, as the delay can give the blood vessels more time to constrict properly. This can help avoid incidents of syncope (fainting).
 * Take a deep breath and flex your abdominal muscles while rising to maintain blood and oxygen in the brain. This, however, may be contraindicated in individuals with Stage 3 hypertension. Usually medical personnel have their patients "dangle" before rising from bed to decrease the likelihood of dizziness / falling due to orthostatic hypotension. The dangling is done by having the patient sit on the side of their bed for about a minute so they do not have the sudden dizziness.
 * Maintaining an elevated salt intake, through sodium supplements or electrolyte-enriched drinks. A suggested value is 10 g per day; overuse can lead to hypertension and should be avoided.
 * Maintaining a proper fluid intake to prevent the effects of dehydration.
 * As eating lowers blood pressure, eat multiple smaller meals rather than fewer larger meals. Take extra care when standing after eating.
 * When orthostatic hypotension is caused by hypovolemia due to medications, the disorder may be reversed by adjusting the dosage or by discontinuing the medication.
 * When the condition is caused by prolonged bed rest, improvement may occur by sitting up with increasing frequency each day. In some cases, physical counterpressure such as elastic hose or whole-body inflatable suits may be required.

Prognosis
The prognosis for individuals with orthostatic hypotension depends on the underlying cause of the condition.