Orthostatic hypotension refers to a reduction of blood pressure (systolic blood pressure that occurs when the heart contracts) of at lest 20 mmHg or a diastolic pressure (pressure when the heart muscle relaxes) of at least 10 mmHg within three minutes of standing.
Orthostatic hypotension is a decrease of blood pressure when standing, due to changes in the blood pressure regulation systems within the body. Normally in a healthy human there is an orthostatic pooling of venous blood in the abdomen and legs when shifting positions from the supine (lying on the back) to an erect position (standing up). This redistribution of blood flow is the result of normal physiological compensatory mechanisms built into
body systems to prevent any adverse outcome (decrease in blood pressure, or hypotension) during positional change. Compensatory mechanisms include sympathetic nervous system activation and parasympathetic inhibition and increased heart rate and vascular resistance. Compensation responses restore cardiac output to vital organs and return blood pressure to normal. Orthostatic hypotension can occur if normal physiological mechanisms become faulty, such as inadequate cardiovascular compensation when shifting positions (i.e. change from supine to erect position), or due to excessive reduction in blood volume. Elderly persons seemed predisposed to orthostatic hypotension because of age-related changes; possible cardiovascular disease and the medications commonly taken by the elderly all predispose autonomic nervous system (ANS) functions. Additionally, hypertension present in 30% of persons over 75 years of age also predisposes a person to orthostatic hypotension, since hypertension reduces
The demographics of orthostatic hypotension are different due to variables that include the subject's position change, the specific population, and when measurements are taken. It is estimated that elderly in community living environments have prevalence rates of approximately 20% among individuals over 65 years of age and 30% in persons over 75 years of age. In frail elderly persons, the prevalence of orthostatic hypotension can be more than 50%. The disorder seems more prevalent among the elderly (especially if systolic blood pressure rises) with chronic diseases (i.e. hypertension and/or diabetes).
Causes and symptoms
Orthostatic hypotension can be caused by several different disorders that affect the entire body (systemic disorders), the central nervous system (CNS, consisting of the brain and spinal cord), and the autonomic nervous system (peripheral autonomic neuropathy) or as a result of taking certain medications that are commonly prescribed by clinicians. Systemic causes can include dehydration, prolonged immobility or an endocrine disorder called adrenal insufficiency. Diseases of the CNS that can cause orthostatic hypotension include MSA (multiple systems atrophy), Parkinson's disease, multiple strokes, brain stem lesions, myelopathy.
Medications that can cause orthostatic hypotension include Tricyclic antidepressants, antipsychotics, monoamine oxidase inhibitors, antihypertensives, diuretics, vasodilators, Levodopa, beta-blockers (heart medications), and blood pressure medications that inhibit a chemical called angiotensin (angiotensin-converting-enzyme inhibitors). Disorders that cause peripheral autonomic neuropathy include diabetes mellitus, amyloidosis, tabes dorsalis (late manifestations of syphilis infection), alcoholism, nutritional deficiency, pure autonomic failure or paraneoplastic syndromes.
The most common symptoms of orthostatic hypotension include weakness, lightheadedness, cognitive impairment, blurred vision, vertigo and tremulousness. Other symptoms that have been reported include headache, paracervical pain, lower back pain, syncope, palpitations, angina pectoris, unsteadiness, falling, and calf claudication.
It is important that the clinician take numerous blood pressure measurements on different occasions, since blood pressure can vary (i.e. postural hypotension, another disorder causing hypotension, is often worse in the morning when rising from bed). A detailed history and physical examination is important. The clinician should focus medical evaluation on autonomic symptoms and diseases. There are bedside tests that can determine autonomic (baroreceptor) response (i.e. Valsalva maneuver). Measurements of a chemical in blood called norepinephrine while lying down and for five to 10 minutes after standing, can produce some useful information concerning deficits in autonomic nervous system functioning. Additionally, levels of another chemical in blood (called vasopressin) during upright tilting, can help to distinguish if the cause is due to ANS failure or from as a result of MSA. Pure ANS failure is characterized by increased vasopressin levels, whereas patients with MSA have no appreciable increase of vasopressin levels during head tilting.
Primary care practitioner (internist); or in complicated cases (severe orthostatic hypotension) a neurologist is consulted.
Nonsymptomatic orthostatic hypotension is a threat for falls or syncope and could be treated by preventive measures that include avoiding warm environments and increasing one's blood pressure by squatting, stooping forward, or crossing one's leg. Additionally, persons affected with the nonsymptomatic variation should increase salt intake, sleep in the head-up position, wear waist-high compression stockings and withdraw from drugs that are known to cause orthostatic hypotension as a side effect. Treatment for symptomatic orthostatic hypotension is important since it is a manifestation of a new illness or as a result of medications. Intervention can initially be nonpharmacologic (preventive measures and adjustments) or pharmacologic therapy. Nonpharmacologic intervention includes a review of medications, since elderly patients may be taking either OTC or prescribed drugs that can induce orthostatic hypotension. Persons affected should rise slowly to the erect position after a long period of sitting or
One of the most commonly prescribed medications for treating orthostatic hypotension is fludrocortisone acetate. This chemical is a synthetic mineralocorticoid which expands circulatory volume. This drug can cause a decrease of an important body element called potassium (hypokalemia, a decrease in potassium in plasma) which is important for normal heart contraction. Elderly persons should be monitored for blood levels of potassium and cardiac status. A drug called midodrine is useful for cases of orthostatic hypotension caused by peripheral autonomic dysfunction, usually in conjunction with fludrocortisone. However, midodrine is not recommended in persons with coronary or peripheral arterial disease. Other medications that may be helpful include clonidine or antihypertension medications. In severe cases of ANS deficits, a combination of medications may be indicated to provide brief periods of upright posture.
Recovery and rehabilitation
The recovery is variable and is also dependent on the cause. Recovery varies according to specific health status of affected person, age complications, and comorbidities (other existing disorders).
Government-sponsored research includes studies concerning treatment of orthostatic hypotension. Details can be obtained from the website: <http://www.clinical trials.gov>
Careful evaluation and management is important for outcome. Identifying the source is an important first step. Preventive measures and posture modification techniques and avoidance of triggers can result in significant reduction of falls, fractures, functional decline, and syncope.
Special attention should be given to medications that are prescribed, which may cause orthostatic hypotension as a side effect.
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American Academy of Neurology. 1080 Montreal Avenue, Saint Paul, MN 55116. 800-879-1960; Fax: (651) 695-2791. <http://www.aan.com>.
Laith Farid Gulli, MD
Alfredo Mori, MBBS