What a Sudden Drop in Blood Pressure Means

In This Article

Sudden drops in blood pressure can occur for any number of reasons, some of which may be incidental and of no real concern, while others may the sign of a potentially life-threatening condition.

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

Sudden drops in blood pressure are often recognized by symptoms ranging from mild lightheadedness and fatigue to severe heart rhythm problems and respiratory distress.

Although low blood pressure (hypotension) is easily diagnosed with a blood pressure cuff (sphygmomanometer), the underlying cause of sudden, severe drops may require extensive investigation, including a physical exam, lab tests, cardiac monitoring, and imaging studies.

Symptoms

Blood pressure is measured by 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 closer to 120/80 mmHg.

Generally speaking, the lower and faster the blood pressure drops, the greater the risk and severity of symptoms. The extent of the drop in pressure also plays a role.

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

Common Symptoms

A sudden drop in blood pressure can manifest with symptoms as the decreased blood flow starves the body of the oxygen and nutrients that it needs to function. Common signs include:

  • Lightheadedness
  • Dizziness
  • Nausea
  • Fatigue
  • Sleepiness
  • Lack of Concentration
  • Blurred Vision
  • Fainting

A plethora of other symptoms may be involved—including chest pain, shortness of breath, irregular heartbeat, hives, fever, indigestion, and vomiting—but 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 and typically manifests with:

  • 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

Sudden hypotension can be broadly categorized by the underlying causes, some of which can overlap, making the diagnosis more difficult.

Hypovolemia

Hypovolemia, a term used to describe reduced blood volume, is the most common cause of hypotension. It results from either excessive loss of fluids or insufficient intake of fluids.

Common causes of hypovolemia include:

  • Dehydration
  • 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)
  • Blood loss, leading to hemorrhagic shock

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 blood volumes are normal, there are conditions that can reduce the body's ability to pump blood. The condition, known as decreased cardiac output, can occur as a result of a heart problem, endocrine (hormonal) dysfunction, and certain medications. Sudden changes in cardiac output can frequently manifest with acute hypotensive symptoms.

Causes of decreased cardiac output include.

Vasodilation

Vasodilation describes the sudden widening of blood vessels due to chemical, neurologic, or immunologic stimuli. With vasodilation, blood pressure will drop in tandem with increases in blood vessel circumference.

Common causes of vasodilation include:

  • Vasodilating drugs: Such as 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: Can lead to septic shock
  • Anaphylaxis: A severe, whole-body allergy that can lead to anaphylactic shock
  • Acidosis: Elevated blood acids
  • Brain or spinal cord injury: Can lead to neurogenic shock

Hypotensive Syndromes

Hypotensive syndromes are interconnected events that bring about a sudden drop in blood pressure. Some of these occur on their own with no underlying disease or long-term consequences. Others occur in response to disease or other external factors.

Hypotensive syndromes tend to come on suddenly with overt and sometimes 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 neurogenerative disorders like Parkinson's disease and Lewy body dementia as well as diabetic nerve damage.
  • Orthostatic hypotension (OH) has the same symptoms as NOH but brought on by non-neurologic causes such as decreased cardiac output, extreme vasodilation, and the chronic use of diuretics, tricyclic antidepressants, and anti-hypertensive drugs. OH and NOH can also be collectively referred to as postural hypotension.
  • 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—decreasing the flow of blood to the heart.
  • Postprandial hypotension occurs after eating when blood is diverted to the intestines to aid in digestion, temporarily robbing 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, leading 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, heart, lungs, and gut to the brain.
  • Situational reflex syncope affects the vagus nerve but is caused when physical stress is placed directly on the nerve. Examples include straining during a bowel movement, lifting a heavy weight, or standing for too long in one place. Urinating after taking a vasodilating drug like Cialis (tadalafil) can also induce reflex syncope.
  • Carotid artery syncope is similar to supine hypotension in that it involves the compression of another major artery, 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 arterial stenosis.

Diagnosis

Hypotension can be readily diagnosed with a blood pressure cuff called a sphygmomanometer. What a sphygmomanometer cannot tell you is the cause of a sudden drop in blood pressure.

For this, the doctor will need to review your medical history, family history, current symptoms, and medication use to draw up a list of possible causes. Among the exams and tests the doctor may order:

  • Valsalva maneuver: An in-office test used to diagnose orthostatic hypotension in which you blow hard through pursed lips to see how it affects your blood pressure and heart rate
  • Blood tests: Used to check for conditions associated with acute hypotension, including diabetes, anemia, hypoglycemia, thyroid problems, kidney impairment, and hormonal imbalances
  • Urinalysis: Used if kidney failure is suspected
  • Electrocardiogram (ECG): Measures electrical activity in the heart to detect rhythm disorders, heart failure, and other cardiovascular disorders
  • Echocardiograms: Uses sound waves to create video images of the heart to detect structural defects like heart valve leakage
  • Imaging tests: X-ray, computed tomography (CT), or magnetic resonance imaging (MRI) used to detect internal bleeding, structural heart problems, kidney problems, or a brain or spinal cord injury
  • Tilt table testing: Measures heart function and blood pressure as the body is tilted into different angles on an adjustable table. It is primarily used to diagnose postural hypotension.
  • Stress testing: Measures a person's heart function and blood pressure while 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 almost invariably requires epinephrine (adrenaline).

If hypotension is related to extreme vasodilation or decreased cardiac output, medications such as vasodilators (like midodrine) or cardiostimulatory drugs (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.

Acute hypotension can usually be treated successfully. The underlying cause, on the other and, may require extensive treatment and the care of a specialist cardiologist, neurologist, or endocrinologist.

A Word From Verywell

It is important not to ignore the signs of hypotension, no matter how subtle they may be. Hypotension may be something you are simply born with or something you can control by hydrating properly. At other times, it may be a sign of something more serious.

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.

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