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Hypotension (Low Blood Pressure)

Posted Jun 23 2009 6:54pm


What Is Hypotension?

Hypotension (HI-po-TEN-shun) is low blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood.

Blood pressure is measured as systolic (sis-TOL-ik) and diastolic (di-a-STOL-ik) pressures. Systolic blood pressure is the pressure when the heart beats while pumping blood. Diastolic blood pressure is the pressure when the heart is at rest between beats.

You will most often see blood pressure numbers written with the systolic number above or before the diastolic, such as 120/80 mmHg. (The mmHg is millimeters of mercury-the units used to measure blood pressure.)

Normal blood pressure in adults is lower than 120/80 mmHg. Hypotension is blood pressure that's lower than 90/60 mmHg.
General idea

Blood pressure changes during the day. It lowers as you sleep and rises when you wake up. It also can rise when you're excited, nervous, or active.

Your body is very sensitive to changes in blood pressure. Special cells in the arteries can sense if your blood pressure begins to rise or fall. When this happens, the cells trigger your body to try to bring blood pressure back to normal.

For example, if you stand up quickly, your blood pressure may drop. The cells will sense the drop and will quickly take action to make sure that blood continues to flow to your brain, kidneys, and other important organs.

Most forms of hypotension happen because your body can't bring blood pressure back to normal or can't do it fast enough.

Some people have low blood pressure all of the time. They have no signs or symptoms, and their low blood pressure is normal for them. In other people, certain conditions or factors cause blood pressure to drop below normal.

Hypotension is a medical concern only if it causes signs or symptoms, such as dizziness, fainting, or, in extreme cases, shock.
Point of View

In a healthy person, low blood pressure without signs or symptoms usually isn't a problem and needs no treatment. If low blood pressure causes signs or symptoms, your doctor will try to find and treat the underlying condition that's causing it.
Hypotension can be dangerous. It can make a person fall because of dizziness or fainting. Shock, a severe form of hypotension, is a condition that's often fatal if not treated right away. With prompt and proper treatment, shock can be successfully treated.

Types of Hypotension

There are several types of hypotension. People who always have low blood pressure have chronic asymptomatic hypotension. They have no signs or symptoms and need no treatment. Their low blood pressure is normal for them.

Other types of hypotension occur only sometimes, when blood pressure suddenly drops too low. The symptoms and effects on the body range from mild to severe.

The three main types of this kind of hypotension are orthostatic (OR-tho-STAT-ik) hypotension, neurally mediated hypotension (NMH), and severe hypotension linked to shock.

Orthostatic Hypotension

This type of low blood pressure occurs when standing up from a sitting or lying down position. It can make you feel dizzy or lightheaded, or even make you faint.

Orthostatic hypotension occurs if your body isn't able to adjust blood pressure and blood flow fast enough for the change in position. This type of low blood pressure usually lasts for only a few seconds or minutes after you stand up. You may need to sit or lie down for a short time while your blood pressure returns to normal.

Orthostatic hypotension can occur in all age groups. However, it's more common in older adults, especially those who are frail or in poor health. It can be a symptom of other medical conditions, and treatment often focuses on treating the underlying condition(s).

Some people have orthostatic hypotension, but also have high blood pressure when lying down.

A form of orthostatic hypotension called postprandial hypotension is a sudden drop in blood pressure after a meal. This type of low blood pressure mostly affects older adults. It's also more likely to affect people who have high blood pressure or a central nervous system disorder, such as Parkinson's disease.
Neurally Mediated Hypotension

With NMH, blood pressure drops after you've been standing for a long time. You may feel dizzy, faint, or sick to the stomach as a result. This type of low blood pressure also can occur if you have an unpleasant, upsetting, or scary experience.

NMH affects children and young adults more often than people in other age groups. Children often outgrow NMH.
Severe Hypotension Linked to Shock

People may say a person has "gone into shock" as a result of an upsetting event. But to doctors, the word "shock" has a different meaning.

Shock is a life-threatening condition in which blood pressure drops so low that the brain, kidneys, and other vital organs can't get enough blood to work properly. Blood pressure drops much lower in shock than in other types of hypotension.

Many factors can cause shock, such as major blood loss, certain severe infections, severe burns and allergic reactions, and poisoning. Shock can be fatal if it's not treated right away.

Other Names for Hypotension

  • Low blood pressure
  • Neurally mediated hypotension
  • Neurogenic orthostatic hypotension
  • Orthostatic hypotension
  • Postprandial hypotension
  • Postural hypotension
  • Shock


What Causes Hypotension?

Factors or conditions that disrupt the body's ability to control blood pressure cause hypotension. The different types of hypotension have different causes.

Orthostatic Hypotension

Orthostatic hypotension has many causes. Sometimes two or more factors combine to cause this type of low blood pressure.

Dehydration (de-hi-DRA-shun) is the most common cause of orthostatic hypotension. Dehydration occurs when the body loses more water than it takes in. You may become dehydrated if you don't drink enough fluids or if you sweat a lot during physical activity. Fever, vomiting, and severe diarrhea also can lead to dehydration.

Orthostatic hypotension may occur during pregnancy, but it generally goes away after the birth.

Because an older body doesn't manage changes in blood pressure as well as a younger body, getting older also can lead to this type of hypotension.

Postprandial hypotension (a type of orthostatic hypotension) mostly affects older adults. Postprandial hypotension is a sudden drop in blood pressure after a meal.

Certain medical conditions can raise your risk for orthostatic hypotension, including:

  • Heart conditions, such as heart attack, heart valve disease, bradycardia (a very low heart rate), and heart failure. These conditions prevent the heart from pumping enough blood to the body.
  • Anemia (uh-NEE-me-eh).
  • Severe infections.
  • Endocrine conditions, such as thyroid disorders, Addison's disease, low blood sugar, and diabetes.
  • Disorders of the central nervous system, such as Parkinson's disease.
  • Pulmonary embolism.

Some medicines used to treat high blood pressure and heart disease can raise your risk for orthostatic hypotension. These medicines include:

  • Diuretics, or "water pills"
  • Calcium channel blockers
  • Angiotensin-converting enzyme (ACE) inhibitors
  • Angiotensin II receptor blockers
  • Nitrates
  • Beta blockers

Medicines used to treat conditions such as anxiety, depression, erectile dysfunction, and central nervous system disorders (like Parkinson's disease) also can increase your risk for orthostatic hypotension.

Other substances, when taken with high blood pressure medicines, also can lead to orthostatic hypotension. These substances include alcohol, barbiturates, and some prescription and over-the-counter medicines.

Finally, other factors or conditions that can trigger orthostatic hypotension include being out in the heat or being immobile (not being able to move around very much) for a long time.

Neurally Mediated Hypotension

Neurally mediated hypotension (NMH) occurs when the brain and heart don't communicate with each other properly.

For example, when you stand for a long time, blood begins to pool in your legs. This causes your blood pressure to drop. In NHM, the body mistakenly tells the brain that blood pressure is high. In response, the brain slows the heart rate. This makes blood pressure drop even more, causing dizziness and other symptoms.

Severe Hypotension Linked to Shock.

Many factors and conditions can cause severe hypotension linked to shock. Some of these factors also can cause orthostatic hypotension. In shock, though, blood pressure drops very low and doesn't return to normal on its own.

Shock is an emergency and must be treated right away. If a person has signs or symptoms of shock.

Certain severe infections can cause shock. This is known as septic shock. It can occur when bacteria enter the bloodstream. The bacteria release a toxin (a poison) that leads to a dangerous drop in blood pressure.

A severe loss of blood or fluids from the body also can cause shock. This is known as hypovolemic (HI-po-vo-LE-mik) shock. Hypovolemic shock can happen as a result of:

  • Major external bleeding (for example, from a severe cut or injury)
  • Major internal bleeding (for example, from a ruptured blood vessel or injury that causes bleeding inside the body)
  • Major loss of body fluids from severe burns
  • Severe swelling of the pancreas (an organ that produces enzymes and hormones, such as insulin)
  • Severe diarrhea
  • Severe kidney disease
  • Overuse of diuretics

A major decrease in the heart's ability to pump blood also can cause shock. This is known as cardiogenic (KAR-de-o-JEN-ik) shock. Heart attack, pulmonary embolism, or arrhythmia (an irregular heartbeat) can cause this type of shock.

A sudden and extreme widening of the arteries and drop in blood pressure also can cause shock. This is known as vasodilatory (VA-so-DI-la-tory) shock. It can occur due to:

  • A severe head injury
  • A reaction to certain medicines
  • Liver failure
  • Poisoning
  • A severe allergic reaction (called anaphylactic (AN-a-fi-LAK-tik) shock)
Who Is At Risk for Hypotension?

Hypotension can affect people of all ages. However, people in certain age groups are more likely to have certain types of low blood pressure.

Older adults are more likely to have orthostatic and postprandial hypotension. Children and young adults are more likely to have neurally mediated hypotension.

People who take certain medicines, such as high blood pressure medicines, are at higher risk for low blood pressure. People who have central nervous system disorders (such as Parkinson's disease) or some heart conditions also are at higher risk for low blood pressure.

Other risk factors for hypotension include being immobile (not being able to move around very much) for long periods and pregnancy. Hypotension during pregnancy is normal and goes away after birth.

What Are the Signs and Symptoms of Hypotension?

Orthostatic Hypotension

The signs and symptoms of orthostatic hypotension may happen within a few seconds or minutes of standing up after you've been sitting or lying down. You may feel that you're going to faint, or you may actually faint. Signs and symptoms include:

  • Dizziness or feeling lightheaded
  • Blurry vision
  • Confusion
  • Weakness
  • Nausea (feeling sick to your stomach)

These signs and symptoms go away if you sit or lie down for a few minutes until your blood pressure adjusts to normal.

Neurally Mediated Hypotension

The signs and symptoms of neurally mediated hypotension (NMH) are similar to those of orthostatic hypotension. They occur after standing for a long time or in response to an unpleasant, upsetting, or scary experience.

The drop in blood pressure with NMH doesn't last long and often goes away after sitting down.

Severe Hypotension Linked to Shock

In shock, not enough blood flows to the major organs, including the brain.

The early signs and symptoms of reduced blood flow to the brain include lightheadedness, sleepiness, and confusion. In the earliest stages of shock, it may be hard to detect any signs or symptoms. In older people, the first symptom may only be confusion.

Over time, as shock worsens, a person won't be able to sit up without passing out. If the shock continues, the person will lose consciousness. Shock is often fatal if not treated right away.

Other signs and symptoms of shock vary, depending on what's causing the shock. When low blood volume (from major blood loss, for example) or poor pumping action in the heart (from heart failure, for example) causes shock:

  • The skin becomes cold and sweaty. It often looks blue or pale. If pressed, the color returns to normal more slowly than usual. A bluish network of lines appears under the skin.
  • The pulse becomes weak and rapid.
  • The person begins to breathe very quickly.

When extreme widening or stretching of blood vessels (such as in septic shock) causes shock, a person feels warm and flushed at first. Later, the skin becomes cold and clammy, and the person feels very sleepy.

How Is Hypotension Diagnosed?

Hypotension is diagnosed based on your medical history, a physical exam, and results from tests. Your doctor will want to know:

  • The type of low blood pressure you have and how severe it is
  • Whether an underlying condition is causing the low blood pressure

Specialists Involved

A primary care doctor or specialist may diagnose and treat hypotension. The type of specialist most commonly involved is a cardiologist (heart specialist).

Other specialists also may be involved, such as surgeons, nephrologists (kidney specialists), neurologists (brain and nerve specialists), or others.

Diagnostic Tests

When a person is in shock, someone should call 9-1-1 right away because emergency treatment is needed.

For other types of hypotension, your doctor may order tests to find out how your blood pressure responds in certain situations. The results will help your doctor understand why you're fainting or having other symptoms.

Blood Tests

During a blood test, a small amount of blood is taken from your body. It's usually drawn from a vein in your arm using a thin needle. The procedure is quick and easy, although it may cause some short-term discomfort.

Blood tests can show whether anemia or low blood sugar is causing your hypotension.

EKG (Electrocardiogram)

An EKG is a simple test that detects and records the heart's electrical activity. It shows how fast the heart is beating and the heart's rhythm (steady or irregular). An EKG also shows the strength and timing of electrical signals as they pass through each part of the heart.

Holter and Event Monitors

Holter and event monitors are medical devices that record the heart's electrical activity. These monitors are similar to an EKG. However, a standard EKG only records the heartbeat for a few seconds. It won't detect heart rhythm problems that don't occur during the test.

Holter and event monitors are small, portable devices. You can wear one while you do your normal daily activities. This allows the monitor to record your heart longer than an EKG can.

Echocardiography

Echocardiography is a test that uses sound waves to create a moving picture of your heart. The picture shows how well your heart is working and its size and shape.

There are several different types of echocardiography, including a stress echocardiogram, or "stress echo." This test is done as part of a stress test (see below). A stress echo usually is done to find out whether you have decreased blood flow to your heart, a sign of coronary artery disease.

Stress Test

Some heart problems are easier to diagnose when your heart is working hard and beating fast. During stress testing, you exercise (or are given medicine if you're unable to exercise) to make your heart work hard and beat fast while heart tests are done.

These tests may include nuclear heart scanning, echocardiography, and magnetic resonance imaging (MRI) and positron emission tomography (PET) scanning of the heart.

Valsalva Maneuver

This is a simple test of the part of your nervous system that controls functions such as your heartbeat and the narrowing and widening of your blood vessels. If something goes wrong with this part of the nervous system, blood pressure problems may occur.

During this test you take a deep breath and then force the air out through your lips. You will do this several times. Your heart rate and blood pressure will be checked during the test.

Tilt Table Test

This test is used if you have fainting spells for no known reason. For the test, you lie on a table that moves from a lying down to an upright position. Your doctor checks your reaction to the change in position.

Doctors use a tilt table test to diagnose orthostatic hypotension and neurally mediated hypotension (NMH). People who have NMH usually faint during this test. The test can help your doctor find any underlying brain or nerve condition.

How Is Hypotension Treated?

Treatment depends on the type of hypotension you have and how severe your signs and symptoms are. The goals of treatment are to relieve signs and symptoms and manage any underlying condition(s) causing the hypotension.

Your response to treatment depends on your age, overall health, and strength. It also depends on how easily you can stop, start, or change medicines.

In a healthy person, low blood pressure without signs or symptoms usually needs no treatment.

If you have signs or symptoms of low blood pressure, you should sit or lie down right away. Put your feet above the level of your heart. If your symptoms don't go away quickly, you should seek medical care right away.

Orthostatic Hypotension

There are a number of treatments for orthostatic hypotension. If you have this type of low blood pressure, your doctor may advise making lifestyle changes such as:

  • Drinking plenty of fluids, like water
  • Drinking little or no alcohol
  • Standing up slowly
  • Not crossing your legs while sitting
  • Gradually sitting up for longer periods if you've been immobile (not able to move around much) for a long time due to a medical condition
  • Eating small, low-carbohydrate meals if you have postprandial hypotension (a form of orthostatic hypotension)

Talk to your doctor about using compression stockings. These stockings apply pressure to your lower legs. They help move blood throughout your body.

If medicine is causing your low blood pressure, your doctor may change the medicine or adjust the dose you take.

Several medicines also are used to treat orthostatic hypotension. These medicines, which raise blood pressure, include fludrocortisone and midodrine.

Neurally Mediated Hypotension

If you have neurally mediated hypotension (NMH), you may need to make lifestyle changes. These may include:

  • Avoiding situations that trigger symptoms. For example, don't stand for long periods. Try to avoid unpleasant, upsetting, or scary situations.
  • Drinking plenty of fluids, like water.
  • Increasing your salt intake (as your doctor advises).
  • Learning to recognize symptoms that occur before fainting and taking action to raise blood pressure. For example, sitting down and putting your head between your knees can help raise blood pressure.
If medicine is causing your low blood pressure, your doctor may change the medicine or adjust the dose you take. He or she also may prescribe a medicine to treat NMH.

Children who have NHM often outgrow it.

Treating Severe Hypotension Linked to Shock

Shock is a life-threatening emergency. People who have shock usually need to be treated in a hospital or by emergency medical personnel.

The goals of treating shock are to:

  • Restore blood flow to the organs as quickly as possible to prevent organ damage
  • Find and reverse the cause of shock
Special fluid or blood injected into the bloodstream is often used to restore blood flow to the organs. Medicines can be used to raise blood pressure or make the heartbeat stronger. Depending on the cause of the shock, other treatments, such as antibiotics or surgery, may be needed.

Key Points

  • Hypotension is low blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood.
  • Normal blood pressure in adults is lower than 120/80 mmHg. Hypotension is blood pressure that's lower than 90/60 mmHg.
  • Some people have low blood pressure all the time. They have no signs or symptoms and their low readings are normal for them. In other people, certain conditions or factors cause blood pressure to drop below normal.
  • In a healthy person, low blood pressure without signs or symptoms usually isn't a problem and needs no treatment.
  • The three main types of hypotension that causes signs and symptoms are orthostatic hypotension, neurally mediated hypotension (NMH), and severe hypotension linked to shock.
  • Orthostatic hypotension is low blood pressure that occurs after standing up from a sitting or lying down position. With NMH, blood pressure drops after you've been standing for a long time or due to severe emotional stress. Shock is a life-threatening condition in which blood pressure drops so low that the brain, kidneys, and other vital organs can't get enough blood to work properly. Many factors can cause shock, such as major blood loss, certain severe infections, severe burns and allergic reactions, and poisoning. Shock can be fatal if not treated right away.
  • Factors or conditions that disrupt the body's ability to control blood pressure cause hypotension. The different types of hypotension have different causes.
  • Hypotension can affect people of all ages. Older adults are more likely to have orthostatic and postprandial hypotension. Children and young adults are more likely to have NMH.
  • The signs and symptoms of orthostatic hypotension and NMH include dizziness or feeling lightheaded, blurry vision, confusion, weakness, and nausea (feeling sick to your stomach). You may feel as though you're going to faint, or you may actually faint. Both of these types of hypotension can be dangerous if a person falls because of the dizziness or fainting.
  • Signs and symptoms of shock include lightheadedness, sleepiness, and confusion. Over time, if shock worsens, a person won't be able to sit up without passing out. If the shock continues, the person can lose consciousness. Other signs and symptoms of shock include cold and sweaty skin, a weak and rapid pulse, and rapid breathing. If a person has signs or symptoms of shock, someone should call 9-1-1 right away.
  • Hypotension is diagnosed based on your medical history, a physical exam, and results from tests.
  • Treatment depends on the type of hypotension you have and how severe your signs and symptoms are. The goals of treatment are to relieve signs and symptoms and manage any underlying condition causing the hypotension. Treatments may include lifestyle changes, compression stockings, procedures, and medicines.
  • Doctors often can successfully treat hypotension. Many people who have the disorder live normal, healthy lives.
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