What is considered low blood pressure (hypotension)? Specifically, what are the generally accepted systolic and diastolic blood pressure ranges that define hypotension in adults? Are these ranges the same for all adults, or do factors like age, fitness level, and pre-existing conditions (like diabetes or heart conditions) influence what is considered “low” for an individual? Furthermore, what are some of the common symptoms associated with low blood pressure, and when should someone experiencing these symptoms seek medical attention?

Answer

Hypotension, or low blood pressure, is generally considered to be present when blood pressure readings consistently fall below 90/60 mmHg (millimeters of mercury). This means a systolic pressure (the top number, measuring pressure when the heart beats) of less than 90 mmHg or a diastolic pressure (the bottom number, measuring pressure when the heart rests between beats) of less than 60 mmHg.

However, the definition of hypotension is not solely based on a specific number. What is considered "low" for one person might be normal for another. Some individuals, particularly athletes or those who are physically fit, may naturally have lower blood pressure without experiencing any symptoms or health problems. In these cases, low blood pressure is not a cause for concern.

The key factor in determining whether low blood pressure is problematic is the presence of symptoms. If low blood pressure is accompanied by symptoms, it may indicate an underlying medical condition or a problem with the body’s ability to maintain adequate blood flow to vital organs.

Common Symptoms Associated with Hypotension:

• Dizziness or lightheadedness: This is one of the most frequent symptoms and often occurs when standing up quickly (orthostatic hypotension).
• Fainting (syncope): A sudden loss of consciousness due to insufficient blood flow to the brain.
• Blurred or distorted vision: Reduced blood flow to the eyes can affect vision.
• Nausea: Hypotension can sometimes lead to feelings of nausea.
• Fatigue: Low blood pressure can cause a general feeling of tiredness or weakness.
• Difficulty concentrating: Insufficient blood flow to the brain can impair cognitive function.
• Cold, clammy, pale skin: Reduced blood flow to the extremities can cause these symptoms.
• Rapid, shallow breathing: The body may attempt to compensate for low blood pressure by increasing the respiratory rate.
• Dehydration and unusual thirst: Hypotension can be caused by or exacerbated by dehydration.

Types of Hypotension:

There are several different types of hypotension, each with its own causes and characteristics:

• Orthostatic Hypotension (Postural Hypotension): This occurs when blood pressure drops suddenly upon standing up from a sitting or lying position. It is common and often temporary. Causes include dehydration, prolonged bed rest, certain medications, and underlying neurological conditions.
• Postprandial Hypotension: This type of hypotension occurs after eating. It is more common in older adults, especially those with high blood pressure or autonomic nervous system disorders. After eating, blood flow increases to the digestive system, which can lead to a drop in blood pressure elsewhere in the body.
• Neurally Mediated Hypotension (NMH): This occurs due to a miscommunication between the heart and the brain. It often happens after standing for long periods.
• Severe Hypotension Related to Shock: This is a dangerous condition caused by a significant drop in blood pressure due to conditions such as:
  • Hypovolemic shock: Caused by severe blood loss (internal or external) or fluid loss (dehydration).
  • Cardiogenic shock: Caused by the heart’s inability to pump enough blood to meet the body’s needs, often due to a heart attack or heart failure.
  • Septic shock: Caused by a severe infection that leads to widespread inflammation and vasodilation (widening of blood vessels).
  • Anaphylactic shock: A severe allergic reaction that causes a sudden drop in blood pressure and difficulty breathing.

Causes of Hypotension:

Numerous factors can contribute to low blood pressure, including:

• Medications: Diuretics (water pills), alpha-blockers, beta-blockers, ACE inhibitors, angiotensin II receptor blockers (ARBs), tricyclic antidepressants, and medications for Parkinson’s disease can lower blood pressure.
• Heart problems: Bradycardia (slow heart rate), heart valve problems, heart attack, and heart failure can impair the heart’s ability to pump blood effectively.
• Endocrine problems: Hypothyroidism (underactive thyroid), adrenal insufficiency (Addison’s disease), low blood sugar (hypoglycemia), and, in some cases, diabetes can contribute to hypotension.
• Dehydration: Insufficient fluid intake can reduce blood volume and lower blood pressure.
• Blood loss: Significant blood loss, whether from injury or internal bleeding, can lead to a drop in blood pressure.
• Severe infection (sepsis): Sepsis can cause widespread vasodilation and a dangerous drop in blood pressure.
• Severe allergic reaction (anaphylaxis): Anaphylaxis can cause a sudden and severe drop in blood pressure.
• Nutritional deficiencies: Lack of vitamin B12 and folate can cause anemia, which can contribute to low blood pressure.
• Pregnancy: Blood pressure often decreases during pregnancy due to hormonal changes and increased blood volume.
• Prolonged bed rest: Extended periods of inactivity can weaken the cardiovascular system and lead to low blood pressure.
• Autonomic nervous system disorders: Conditions like Parkinson’s disease and diabetic neuropathy can affect the autonomic nervous system, which regulates blood pressure.

Diagnosis of Hypotension:

Diagnosing hypotension typically involves:

• Blood pressure measurement: Taking blood pressure readings at different times of the day and in different positions (lying down, sitting, standing) to assess for orthostatic hypotension.
• Medical history and physical examination: The doctor will ask about symptoms, medical history, and medications. A physical exam helps identify potential underlying causes.
• Blood tests: These can help rule out anemia, endocrine problems, infections, and other conditions that can cause hypotension.
• Electrocardiogram (ECG or EKG): This test measures the electrical activity of the heart and can help identify heart problems that may be contributing to low blood pressure.
• Tilt table test: This test is used to evaluate neurally mediated hypotension. The patient lies on a table that is tilted to simulate the change in position from lying down to standing. Blood pressure and heart rate are monitored during the test.

Treatment of Hypotension:

Treatment for hypotension depends on the underlying cause and the severity of symptoms. In many cases, lifestyle modifications can help manage low blood pressure:

• Increase fluid intake: Drinking plenty of water can help increase blood volume.
• Increase salt intake: Salt helps retain fluid in the bloodstream and can raise blood pressure. However, this should be done under the guidance of a doctor, especially for individuals with heart failure or kidney disease.
• Wear compression stockings: These can help improve blood circulation in the legs and prevent blood from pooling.
• Avoid prolonged standing or sitting: Take breaks and move around to prevent blood from pooling in the legs.
• Stand up slowly: To avoid orthostatic hypotension, rise slowly from a lying or sitting position.
• Avoid alcohol: Alcohol can dilate blood vessels and lower blood pressure.
• Eat small, frequent meals: This can help prevent postprandial hypotension.
• Adjust medications: If medications are contributing to low blood pressure, the doctor may adjust the dosage or switch to a different medication.

In some cases, medications may be prescribed to treat hypotension:

• Fludrocortisone: This medication helps the body retain sodium and fluid, which can increase blood pressure.
• Midodrine: This medication constricts blood vessels, which can raise blood pressure.

When to Seek Medical Attention:

It’s important to seek medical attention if you experience persistent symptoms of low blood pressure, such as dizziness, lightheadedness, fainting, blurred vision, nausea, or fatigue. It is especially important to seek immediate medical attention if you experience:

• Chest pain
• Shortness of breath
• Severe dizziness or fainting
• Rapid or irregular heartbeat
• Confusion
• Difficulty speaking