Orthostatic hypotension

Definition

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.

Description

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 baroreflex sensitivity. Hypertension and the normal aging process (which typically causes blood vessel stiffness) decrease the sensitivity of specialized structures called baroreceptors, which function to maintain blood pressure, but initiating compensatory mechanisms such as increasing heart rate and vascular resistance. Persons affected with symptomatic orthostatic hypotension have symptoms when tilting head upward or when moving toward an erect position. Symptom severity varies among affected persons, but can include blurred vision, light-headedness, weakness, vertigo, tremulousness and cognitive impairment. Symptoms can be relieved within one minute of lying down. Some persons have orthostatic hypertension without symptoms.

Demographics

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.

Diagnosis

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.

Treatment team

Primary care practitioner (internist); or in complicated cases (severe orthostatic hypotension) a neurologist is consulted.

Treatment

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 lying down. They should avoid excess heat environments (i.e. in shower or central heating systems), coughing, straining or heavy lifting since these events can precipitate episodes of orthostatic hypotension. There are certain measures that can redirect blood to increase blood pressure and reduce symptoms associated with orthostatic hypotension. These measures include squatting, sitting down, crossing legs, and stooping forward.

Pharmacological Treatment

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).

Clinical trials

Government-sponsored research includes studies concerning treatment of orthostatic hypotension. Details can be obtained from the website: <http://www.clinical trials.gov>

Prognosis

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 concerns

Special attention should be given to medications that are prescribed, which may cause orthostatic hypotension as a side effect.

Resources

BOOKS

Goetz, Christopher G., et al, eds. Textbook of Clinical Neurology, 1st ed. Philadelphia: W.B. Saunders Company, 1999.

Marx, John A., et al eds. Rosen's Emergency Medicine: Concepts and Clinical Practice, 5th ed. St. Louis: Mosby, Inc., 2002.

Noble, John., et al eds. Textbook of Primary Care Medicine, 3rd ed. St. Louis: Mosby, Inc., 2001.

PERIODICALS

Mukai, Seiji, and Lewis A. Lipsitz. "Orthostatic Hypotension." Clinics in Geriatric Medicine 18:2: (May 2002).

Viramo, Petteri. "Orthostatic Hypotension and Cognotive Decline in Older People." Journal of the American Geriatrics Society 47:5 (May 1999).

The Consensus Committee of the American Autonomic Society and the American Academy of Neurology. "Consensus statement on the definition of orthostatic hypotension, pure autonomic failure, and multiple system atrophy." Neurology 46:5 (May 1996).

WEBSITES

The Family Practice Notebook.com. Orthostatic Hypotension. <http://www.fpnotebook.com>.

ORGANIZATIONS

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

Orthostatic Hypotension

Definition

Orthostatic hypotension is an abnormal decrease in blood pressure when a person stands up. This may lead to fainting.

Description

When a person stands upright, a certain amount of blood normally pools in the veins of the ankles and legs. This pooling means that there is slightly less blood for the heart to pump and causes a drop in blood pressure. Usually, the body responds to this drop so quickly, a person is unaware of the change. The brain tells the blood vessels to constrict so they have less capacity to carry blood, and at the same time tells the heart to beat faster and harder. These responses last for a very brief time. If the body's response to a change in vertical position is slow or absent, the result is orthostatic hypotension. It is not a true disease, but the inability to regulate blood pressure quickly.

Causes and symptoms

Orthostatic hypotension has many possible causes. The most common cause is medications used to treat other conditions. Diuretics reduce the amount of fluid in the body which reduces the volume of blood. Medicines used to expand the blood vessels increase the vessel's ability to carry blood and so lower blood pressure.

If there is a severe loss of body fluid from vomiting, diarrhea, untreated diabetes, or even excessive sweating, blood volume will be reduced enough to lower blood pressure. Severe bleeding can also result in orthostatic hypotension.

Any disease or spinal cord injury that damages the nerves which control blood vessel diameter can cause orthostatic hypotension.

Symptoms of orthostatic hypotension include faintness, dizziness, confusion, or blurry vision, when standing up quickly. An excessive loss of blood pressure can cause a person to pass out.

Diagnosis

When a person experiences any of the symptoms above, a physician can confirm orthostatic hypotension if the person's blood pressure falls significantly on standing up and returns to normal when lying down. The physician will then look for the cause of the condition.

Treatment

When the cause of orthostatic hypotension is related to medication, it is often possible to treat it by reducing dosage or changing the prescription. If it is caused by low blood volume, an increase in fluid intake and retention will solve the problem.

Medications designed to keep blood pressure from falling can be used when they will not interfere with other medical problems.

When orthostatic hypotension cannot be treated, the symptoms can be significantly reduced by remembering to stand up slowly or by wearing elastic stockings.

Prognosis

The prognosis for people who have orthostatic hypotension depends on the underlying cause of the problem.

Prevention

There is no way to prevent orthostatic hypotension, since it is usually the result of another medical condition.

Resources

ORGANIZATIONS

National Heart, Lung and Blood Institute. P.O. Box 30105, Bethesda, MD 20824-0105. (301) 251-1222. 〈http://www.nhlbi.nih.gov〉.

National Organization for Rare Disorders. P.O. Box 8923, New Fairfield, CT 06812-8923. (800) 999-6673. 〈http://www.rarediseases.org〉.