Low Blood Pressure

Definition

Hypotension is the medical term for low blood pressure, generally considered to be a systolic blood pressure of 90 mm Hg or less in an adult.

However, some normal adults may have levels that low without any symptoms, while some hypertensive patients may develop shock with what would be considered normal blood pressure.

Description

Blood pressures vary, depending on such factors as age, race, sex, and environment. On rare occasions, individuals may have medical problems that cause low blood pressure. Among such conditions are some types of heart disease, hormonal deficiencies, and malnutrition. In these cases, the hypotension will be corrected by the treatment of the medical problem.

High blood pressure is recognized as a potentially life-threatening condition for which medical intervention is appropriate.

Whether low blood pressure produces a syndrome is controversial. Several studies have suggested that low blood pressure may be associated with nonspecific symptoms such as tiredness and feeling faint. Because these symptoms are often attributed to psychological problems, some authorities believe that psychological dysfunction may be associated with hypotension.

Postural (orthostatic) Hypotension

Postural or orthostatic hypotension is a form of low blood pressure in which dizziness or faintness occurs when a person stands up abruptly from a sitting or reclining position. Normally, when an individual stands up, the blood vessels constrict to maintain normal blood pressure in the new position. However, in persons with postural hypotension, this mechanism probably does not work properly, and on standing, a temporary reduction in the blood flow to the brain may lead to fainting. Rising slowly from a sitting or reclining position will usually prevent the symptoms in this situation.

Patients with any form of orthostatic hypotension usually present with similar symptoms. On assuming an upright posture they may experience lightheadedness, dizziness, syncope (fainting), swaying, focal cerebral ischemia (low blood flow) manifested by receptive or expressive aphasia (difficulty communicating) or seizures (usually clonic jerks), angina pectoris, headache referred to the back of the head or neck, or tunnel vision.

Although postural hypotension is a benign condition in most individuals, it should be reported to a physician.

Causes

The likelihood of syncope (fainting) is increased after meals, in hot environments such as after showers, and after consuming alcohol.

Sometimes postural hypotension results from taking a medication for high blood pressure; in these cases, the physician may reduce the dosage or change the medication. Fluids, including blood, lost from the body may also cause postural hypotension, as may many diseases. Hypotension can occur in combination with Addison's disease and alcoholism.

Treatment

Treatment varies depending on the cause of the low blood pressure. If you have no symptoms, your physician may decide no treatment is necessary. If you have symptoms, your physician may reassess the doses of your medications, especially your blood pressure medications.

In orthostatic (postural) hypotension, possible interventions may include rehydration, changing the timing of meals, elevation of the head of your bed, and pressure-graded stockings.