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What Is Hypotension?

Hypotension (HI-po-TEN-shun) is abnormally 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" refers to blood pressure when the heart beats while pumping blood. "Diastolic" refers to blood pressure when the heart is at rest between beats.

You most often will see blood pressure numbers written with the systolic number above or before the diastolic number, 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.

Overview

Blood pressure doesn't stay the same all the time. It lowers as you sleep and rises when you wake up. Blood pressure also rises when you're excited, nervous, or active.

Your body is very sensitive to changes in blood pressure. For example, if you stand up quickly, your blood pressure may drop for a short time. Your body adjusts your blood pressure to make sure enough blood and oxygen are flowing to your brain, kidneys, and other vital 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 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 abnormally low blood pressure. As a result, less blood and oxygen flow to the body's organs.

For the most part, hypotension is a medical concern only if it causes signs or symptoms or is linked to a serious condition, such as heart disease. Signs and symptoms of hypotension may include dizziness, fainting, cold and sweaty skin, fatigue (tiredness), blurred vision, or nausea (feeling sick to your stomach).

In extreme cases, hypotension can lead to shock.

Outlook

In a healthy person, low blood pressure without signs or symptoms usually isn't a problem and needs no treatment. If it causes signs or symptoms, your doctor will try to find and treat the condition that's causing it.

Hypotension can be dangerous. It can make you 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 usually have no signs or symptoms and need no treatment. Their low blood pressure is normal for them.

Other types of hypotension occur if blood pressure suddenly drops too low. The signs and symptoms range from mild to severe.

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

Orthostatic Hypotension

This type of hypotension occurs when standing up from a sitting or lying down position. You may feel dizzy or light-headed, or you may even faint.

Orthostatic hypotension occurs if your body isn't able to adjust blood pressure and blood flow fast enough for the change in position. The drop in blood pressure usually lasts only for 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. This type of hypotension can be a symptom of another medical condition. Thus, treatment often focuses on treating underlying conditions.

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 hypotension mostly affects older adults. People who have high blood pressure or a central nervous system disorder, such as Parkinson's disease, also are at increased risk for postprandial hypotension.

Neurally Mediated Hypotension

With neurally mediated hypotension (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. NMH also can occur as the result of an unpleasant, upsetting, or scary situation.

NMH affects children and young adults more often than people in other age groups. Children often outgrow NMH.

Severe Hypotension Linked to Shock

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 well. Blood pressure drops much lower in shock than in other types of hypotension.

Many factors can cause shock. Examples include 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?

Conditions or factors 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 if 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 cause dehydration.

Orthostatic hypotension also may occur during pregnancy, but it usually goes away after 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 of orthostatic hypotension, including:

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

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

Medicines for conditions such as anxiety, depression, erectile dysfunction, and central nervous system disorders also can increase your risk of 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 for a long time. "Immobile" means you can't move around very much.

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 NMH, 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, call 9–1–1.

Some severe infections can cause shock. This is known as septic shock. It can occur if bacteria enter the bloodstream. The bacteria release a toxin (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.

A heart attack, pulmonary embolism, or an ongoing arrhythmia (ah-RITH-me-ah) that disrupts heart function can cause this type of shock.

A sudden and extreme relaxation of the arteries linked to a 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 hypotension.

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 diuretics ("water pills") or other high blood pressure medicines—are at increased risk for hypotension. Certain conditions also increase the risk for hypotension. Examples include central nervous system disorders (such as Parkinson's disease) and some heart conditions.

Other risk factors for hypotension include being immobile (not being able to move around very much) for long periods, being out in the heat for a long time, and pregnancy. Hypotension during pregnancy is normal and usually goes away after birth.




What Are the Signs and Symptoms of Hypotension?

Orthostatic Hypotension and Neurally Mediated Hypotension

The signs and symptoms of orthostatic hypotension and neurally mediated hypotension (NMH) are similar. They include:

  • Dizziness or light-headedness
  • Blurry vision
  • Confusion
  • Weakness
  • Fatigue (feeling tired)
  • Nausea (feeling sick to your stomach)

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

The signs and symptoms of NMH occur after standing for a long time or in response to an unpleasant, upsetting, or scary situation. 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 and oxygen flow to the body's major organs, including the brain. The early signs and symptoms of reduced blood flow to the brain include light-headedness, 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 often is 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 relaxation of blood vessels causes shock (such as in vasodilatory shock), a person feels warm and flushed at first. Later, the skin becomes cold and sweaty, and the person feels very sleepy.

Shock is an emergency and must be treated right away. If a person has signs or symptoms of shock, call 9–1–1.




How Is Hypotension Diagnosed?

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

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

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), or neurologists (brain and nerve specialists).

Diagnostic Tests

Shock is a life-threatening condition that requires emergency treatment. For other types of hypotension, your doctor may recommend tests to find out how your blood pressure responds in certain situations.

The test 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 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 your heart's electrical activity. It shows how fast your heart is beating and whether its rhythm is steady or irregular. An EKG also shows the strength and timing of electrical signals as they pass through each part of your heart.

Holter and Event Monitors

Holter and event monitors are medical devices that record your heart's electrical activity. These monitors are similar to an EKG. However, a standard EKG only records your 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 for longer periods than a standard EKG.

Echocardiography

Echocardiography (echo) 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 types of echo, including stress echo. This test is done as part of a stress test (see below). Stress echo usually is done to find out whether you have decreased blood flow to your heart, a sign of coronary heart disease (also called 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, echo, and positron emission tomography (PET) scanning of the heart.

Valsalva Maneuver

This is a simple test for 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 the severity of your signs and symptoms. The goal of treatment is to bring blood pressure back to normal to relieve signs and symptoms. Another goal is to manage any underlying condition 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 isn't a problem and needs no treatment.

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

Orthostatic Hypotension

Many treatments are available for orthostatic hypotension. If you have this condition, your doctor may advise making lifestyle changes, such as:

  • Drinking plenty of fluids, such as water or sports drinks that contain nutrients like sodium and potassium.
  • Drinking little or no alcohol.
  • Standing up slowly.
  • Not crossing your legs while sitting.
  • Slowly increasing the amount of time you sit up if you've been immobile for a long time because of a medical condition. The term "immobile" refers to not being able to move around very much.
  • Eating small, low-carbohydrate meals if you have postprandial hypotension (a form of orthostatic hypotension).

Talk with your doctor about using compression stockings. These stockings apply pressure to your lower legs. The pressure helps 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 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, such as standing for long periods. Unpleasant, upsetting, or scary situations also can trigger symptoms.
  • Drinking plenty of fluids, such as water or sports drinks that contain nutrients like sodium and potassium.
  • Increasing your salt intake (as your doctor advises).
  • Learning to recognize symptoms that occur before fainting and taking action to raise your blood pressure. For example, sitting down and putting your head between your knees or lying down can help raise blood pressure.

If medicine is causing your hypotension, your doctor may change the medicine or adjust the dose you take. He or she also may prescribe medicine to treat NMH.

Children who have NHM often outgrow it.

Severe Hypotension Linked to Shock

Shock is a life-threatening emergency. People who have shock need prompt treatment from medical personnel. If a person has signs or symptoms of shock, call 9–1–1 right away.

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

Blood or special fluids are put into the bloodstream to restore blood flow to the organs. Medicines can help 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.




Living With Hypotension

Doctors can successfully treat hypotension. Many people who had the condition and were successfully treated live normal, healthy lives.

If you have hypotension, you can take steps to prevent or limit symptoms, such as dizzy spells and fainting.

If you have orthostatic hypotension, get up slowly after sitting or lying down, or move your legs before changing your position. Eat small, low-carbohydrate meals if you have postprandial hypotension (a form of orthostatic hypotension).

If you have neurally mediated hypotension, try not to stand for long periods. If you do have to stand for a long time, move around and wear compression stockings. These stockings apply pressure to your lower legs. The pressure helps move blood throughout your body.

Drink plenty of fluids, such as water or sports drinks that contain nutrients like sodium and potassium. Also, try to avoid unpleasant, upsetting, or scary situations. Learn to recognize symptoms and take action to raise your blood pressure. Children who have NMH often outgrow it.

Other lifestyle changes also can help you control hypotension. For more information, talk with your doctor and go to "How Is Hypotension Treated?"

Ask your doctor about learning how to measure your own blood pressure. This will help you find out what a normal blood pressure reading is for you. Keeping a record of blood pressure readings done by health providers also can help you learn more about your blood pressure.

Severe hypotension linked to shock is an emergency. Shock can lead to death if it's not treated right away. If you see someone having signs or symptoms of shock, call 9–1–1.

Signs and symptoms of shock include light-headedness, sleepiness, and confusion. Over time, as 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.




Clinical Trials

The National Heart, Lung, and Blood Institute (NHLBI) is strongly committed to supporting research aimed at preventing and treating heart, lung, and blood diseases and conditions and sleep disorders.

NHLBI-supported research has led to many advances in medical knowledge and care. Often, these advances depend on the willingness of volunteers to take part in clinical trials.

Clinical trials test new ways to prevent, diagnose, or treat various diseases and conditions. For example, new treatments for a disease or condition (such as medicines, medical devices, surgeries, or procedures) are tested in volunteers who have the illness. Testing shows whether a treatment is safe and effective in humans before it is made available for widespread use.

By taking part in a clinical trial, you can gain access to new treatments before they're widely available. You also will have the support of a team of health care providers, who will likely monitor your health closely. Even if you don't directly benefit from the results of a clinical trial, the information gathered can help others and add to scientific knowledge.

If you volunteer for a clinical trial, the research will be explained to you in detail. You'll learn about treatments and tests you may receive, and the benefits and risks they may pose. You'll also be given a chance to ask questions about the research. This process is called informed consent.

If you agree to take part in the trial, you'll be asked to sign an informed consent form. This form is not a contract. You have the right to withdraw from a study at any time, for any reason. Also, you have the right to learn about new risks or findings that emerge during the trial.

For more information about clinical trials related to hypotension, talk with your doctor. You also can visit the following Web sites to learn more about clinical research and to search for clinical trials:

For more information about clinical trials for children, visit the NHLBI's Children and Clinical Studies Web page.




Links to Other Information About Hypotension

NHLBI Resources

Non-NHLBI Resources

Clinical Trials

 
November 01, 2010 Last Updated Icon

The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.

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