What a Sudden Drop in Blood Pressure Means

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A sudden drop in blood pressure, also called hypotension, can occur for any number of reasons. Some may be of no real concern, while others may be a sign of a potentially life-threatening condition.

This article will cover the various causes of low blood pressure, possible symptoms, and treatment options.

A woman having her blood pressure taken
Jose Luis Pelaez Inc. / Getty Images

Symptoms

Blood pressure is measured in millimeters of mercury (mmHg). Hypotension is usually defined as a systolic (upper) value of 90 mmHg and a diastolic (lower) value of 60 mmHg. Normal blood pressure is considered 120/80 mmHg or below.

However, blood pressure that's too far below that number can lead to problems. Generally speaking, the lower and faster the blood pressure drops, the more severe the symptoms will be. The extent of the drop in pressure also plays a role.

For example, if you have high blood pressure (hypertension) and the pressure suddenly drops to below 90/60 mmHg, you are more likely to experience noticeable symptoms than if it were to drop from, say, 110/70 mmHg.

Sudden (also called acute) drops in blood pressure can cause symptoms ranging from mild lightheadedness and fatigue to severe heart rhythm problems and respiratory distress.

Common Symptoms

When blood pressure drops suddenly, blood flow to the body decreases. This starves the body of the oxygen and nutrients that it needs to function. The lack of blood flow to the brain especially triggers symptoms.

Common signs include:

  • Lightheadedness
  • Dizziness
  • Nausea
  • Fatigue
  • Sleepiness
  • Difficulty concentrating
  • Blurred vision
  • Fainting

Other symptoms that can occur include chest pain, shortness of breath, irregular heartbeat, hives, fever, indigestion, and vomiting. These tend to be associated with the condition that caused the drop in the first place.

Severe Symptoms

Extreme hypotension can severely deprive the brain and vital organs of oxygen and nutrients, leading to shock. Shock can progress rapidly. Symptoms include:

  • Extreme weakness
  • Extreme anxiety
  • Rapid heart rate
  • Weak pulse
  • Rapid, shallow breathing
  • Profuse sweating
  • Increased thirst
  • Cold, clammy skin
  • Confusion

Call 911 or go to your nearest emergency room if signs of shock develop. If left untreated, shock can lead to permanent organ damage, cardiac arrest, and even death.

Causes

There are several possible causes of hypotension. Some of them can overlap, making the diagnosis more difficult. Causes include:

Hypovolemia

Hypovolemia is a term used to describe reduced blood volume. This is the most common cause of hypotension. It can occur if you are not getting enough fluids or if your body is losing too much fluid.

Common causes of hypovolemia include:

  • Dehydration
  • Blood loss, leading to hemorrhagic shock
  • Starvation or fasting
  • Severe diarrhea or vomiting
  • Heatstroke
  • Excessive use of diuretics ("water pills")
  • Kidney failure
  • Severe pancreatitis (causing the leakage of fluid into the abdominal cavity)

Hypovolemic shock occurs when you lose more than 20% of your blood volume for any reason. A loss at this level makes it impossible for the heart to pump a sufficient amount of blood through the body.

Decreased Cardiac Output

Even if your blood volume is normal, there are conditions that can reduce the body's ability to pump blood. This condition is known as decreased cardiac output.

It can occur as a result of a heart problem, endocrine (hormonal) dysfunction, and certain medications. Sudden changes in cardiac output can cause a sudden drop in blood pressure.

Causes of decreased cardiac output include.

Vasodilation

Vasodilation describes the sudden widening of blood vessels. As the blood vessels get wider, blood pressure continues to drop.

Common causes of vasodilation include:

  • Vasodilating drugs: Drugs in this category include calcium channel blockers, angiotensin II receptor blockers, nitroglycerin, nitrous oxide, Rogaine (minoxidil), and Viagra (sildenafil).
  • Dysautonomia: A condition in which which the autonomic nervous system malfunctions, affecting the heart, bladder, intestines, blood vessels, and other organs
  • Sepsis: A life-threatening reaction to an infection
  • Anaphylaxis: A severe, whole-body allergy that can lead to anaphylactic shock
  • Acidosis: A condition in which blood acids are elevated
  • Neurogenic shock: Shock caused by a brain or spinal cord injury

Hypotensive Syndromes

A hypotensive syndrome is the term used when more than one factor causes a sudden drop in blood pressure. Usually the person has an underlying condition that is then triggered by doing something such as standing up after sitting or experiencing severe emotional distress.

Hypotensive syndromes tend to come on suddenly, sometimes with dramatic symptoms, including extreme dizziness and unconsciousness.

Some common hypotensive syndromes include:

  • Neurogenic orthostatic hypotension (NOH) is when a change in body position, such as rising from a chair or bed, causes a dramatic drop in blood pressure. NOH is caused by an underlying neurologic disorder that affects the autonomic nervous system. It is common with neurodegenerative disorders like Parkinson's disease and Lewy body dementia as well as diabetic nerve damage.
  • Orthostatic hypotension (OH) has the same symptoms as NOH. It is brought on by non-neurologic causes such as decreased cardiac output and extreme vasodilation. Drugs such as diuretics, tricyclic antidepressants, and medications for high blood pressure can also cause OH.
  • Supine hypotensive syndrome occurs in later pregnancy when the weight of the baby presses down on two of the largest blood vessels in the body, the aorta and the inferior vena cava. This decreases the flow of blood to the heart.
  • Postprandial hypotension occurs after eating. Blood is diverted to the intestines to help digestion. This temporarily robs the brain of blood and oxygen. It is most common in the elderly and generally occurs within 30 to 75 minutes of eating.
  • Vasovagal syncope is an overreaction to certain triggers, such as the sight of blood or extreme emotional distress. This leads to a steep drop in blood pressure and fainting (syncope). It is caused by the overactivation of the vagus nerve, which relays nerve signals from the heart, liver, lungs, and gut to the brain.
  • Situational reflex syncope affects the vagus nerve. It can occur when physical stress is placed directly on the nerve. Straining during a bowel movement, lifting a heavy weight, or standing for too long in one place can cause this to happen. Urinating after taking a vasodilating drug like Cialis (tadalafil) can also trigger reflex syncope.
  • Carotid artery syncope involves the compression of the internal carotid artery of the neck. Wearing a tight collar, shaving, or turning the head can cause a sudden drop in blood pressure, especially in older people or those with carotid artery stenosis.

Recap

In people with certain diseases or conditions, doing something as simple as rising from a chair or turning the head can trigger a sudden drop in blood pressure. This is known as a hypotensive syndrome.

Diagnosis

A blood pressure cuff called a sphygmomanometer can tell you how low your blood pressure is, but it can't tell you what caused the sudden drop.

For this, the doctor will need to review your medical history, family history, current symptoms, and medications. Then they will perform some of the following tests to figure out the cause:

  • Valsalva maneuver: An in-office test used to diagnose orthostatic hypotension. You blow hard through pursed lips to see how it affects your blood pressure and heart rate.
  • Blood tests: Blood test results can reveal conditions associated with acute hypotension. These include diabetes, anemia, hypoglycemia, thyroid problems, kidney problems, and hormonal imbalances.
  • Urinalysis: A urine test can help diagnose kidney disease.
  • Electrocardiogram (ECG): An ECG measures electrical activity in the heart to detect rhythm disorders, heart failure, and other cardiovascular problems.
  • Echocardiogram: This test uses sound waves to create video images of the heart to detect structural defects like heart valve leakage.
  • Imaging tests: Computed tomography (CT), magnetic resonance imaging (MRI), and X-rays are used to detect internal bleeding, structural heart problems, kidney problems, or a brain or spinal cord injury.
  • Tilt table testing: This measures heart function and blood pressure as the body is tilted at different angles on an adjustable table. It is mostly used to diagnose postural hypotension.
  • Stress testing: A stress test measures a person's heart function and blood pressure while they are running on a treadmill or pedaling a stationary bike. It is primarily used to diagnose coronary artery disease.

Treatment

The treatment of acute hypotension varies based on the underlying cause. If the condition is not a medical emergency, you should either sit or lie down immediately and raise your feet above heart level. If you are dehydrated, you should replenish lost fluids and seek immediate medical attention if the symptoms are severe.

If hypovolemic or hemorrhagic shock is involved, you may be given an intravenous (IV) saline solution or a blood transfusion. Septic shock may require IV antibiotics, while anaphylactic shock requires epinephrine (adrenaline).

If hypotension is related to extreme vasodilation or decreased cardiac output, medications such as vasodilators (like midodrine) or drugs to stimulate the heart (like digitalis) may be prescribed to improve heart function and output.

People with severe postural hypotension may benefit from the use of the anti-inflammatory steroid fludrocortisone.

Compression socks are often prescribed for people with orthostatic hypotension to prevent the pooling of blood in the legs. Wearing them keeps more blood in the upper body.

Summary

A sudden drop in blood pressure can occur for a variety of reasons. Some of these are not serious. In some cases, though, it may be a sign of something more serious, and even life-threatening. Serious underlying causes usually have other symptoms.

Hypotension can often be treated successfully. The underlying cause, on the other hand, may require extensive treatment by a specialist, such as a cardiologist, neurologist, or endocrinologist.

A Word From Verywell

It is important not to ignore signs of hypotension. This is especially true if the drop is sudden and severe. By seeing a doctor and pinpointing the cause of acute hypotension, you can be treated appropriately and avoid any long-term harm to your health.

Frequently Asked Questions

  • What is orthostatic hypotension?

    Orthostatic hypotension is a sudden drop in blood pressure that occurs when you change your posture: rising from a lying position, standing from a seated position. It usually occurs as soon as you change your position, but it may happen several moments later.

  • What should you do if your blood pressure suddenly drops?

    In cases of sudden hypotension, sit down or lie down immediately and raise your feet above the level of your heart. If the incident is caused by shock, you may need to be given medication to increase blood pressure or treat an underlying illness. If a person loses consciousness due to low blood pressure, get emergency assistance immediately.

  • What is a low blood pressure reading?

    Low blood pressure occurs when the systolic blood pressure (the top number) is lower than 90 or diastolic blood pressure (the bottom number) is lower than 60.

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