Hypotension

Hypotension is abnormally low blood pressure.​

Blood pressure is the force of your blood pushing against the walls of your arteries. Each time your heart beats, it pumps out blood into the arteries.

Your blood pressure is highest when your heart beats, pumping the blood. This is called systolic pressure. When your heart is at rest, between beats, your blood pressure falls. This is the diastolic pressure. Your blood pressure reading uses these two numbers. Usually they're written one above or before the other, such as 120/80. If your blood pressure reading is 90/60 or lower, you have low blood pressure.

Some people have low blood pressure all the time. They have no symptoms and their low readings are normal for them. In other people, blood pressure drops below normal because of a medical condition or certain medicines. Some people may have symptoms of low blood pressure when standing up too quickly. Low blood pressure is a problem only if it causes dizziness, fainting or in extreme cases, shock.

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.

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. 

Dehydration is the most common cause of orthostatic hypotension. 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:

  • 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.
  • Severe infections.
  • Endocrine conditions, such as thyroid disorders, Addison's disease, low blood sugar, and diabetes.
  • Central nervous system disorders, such as Parkinson's disease.
  • Pulmonary embolism.

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

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.

Other Causes 

Some severe infections can cause shock. This is known as septic shock.

A severe loss of blood or fluids from the body also can cause shock. This is known as hypovolemic 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 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 shock. It can occur due to:

  • A severe head injury
  • A reaction to certain medicines
  • Liver failure
  • Poisoning

A severe allergic reaction, called anaphylactic shock.

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
  • Nausea

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.

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

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

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.

Treatment depends on the type of hypotension you have and the severity of your signs and symptoms. 

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. 
  • 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.

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
  • 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.

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.

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.

 

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.

Other signs and symptoms of shock include cold and sweaty skin, a weak and rapid pulse, and rapid breathing.