Hypotension is the medical term for low blood pressure. Blood pressure is the force of blood pushing against the walls of arteries (blood vessels). Each time the heart beats, it pumps blood through blood vessels, supplying the body's muscles, organs, and tissues with the oxygen and nutrients that they need to function. Throughout the day, an individual's blood pressure rises and falls many times in response to various factors. For instance, stress typically increases blood pressure, and patients generally have lower blood pressure during sleep.
Blood pressure is represented as two numbers: systolic pressure over diastolic pressure. These numbers are measured in millimeters of mercury (mmHg). Systolic pressure indicates the amount of pressure that the heart produces when it is pumping blood throughout the body. Diastolic pressure indicates the amount of pressure in the arteries when the heart is resting between beats.
Normal blood pressure is considered lower than 120/80 millimeters of mercury. Many experts consider 115/75 millimeters of mercury to be optimal. It is important to note that this target blood pressure may be different for people with chronic illnesses, such as diabetes. If a person's blood pressure it less than 90/60 millimeters of mercury, it is considered lower than normal. Having just one number in the low range is considered low.
Unlike high blood pressure, most doctors diagnose low blood pressure based on the symptoms rather than the value. This is because low blood pressure without symptoms is not generally a cause for concern. In fact, many athletes have low blood pressure and have a decreased risk of developing heart disease. Symptoms of low blood pressure occur when the blood flow is so low that the vital organs (such as the brain, heart, and kidneys) are unable to get enough oxygen and nutrients from the blood to function normally. Health problems are most likely to occur if blood pressure drops suddenly in response to an underlying medical problem, such as a severe allergic reaction or widespread infection.
There are many potential causes of hypotension, such as allergic reactions, excessive blood loss, endocrine problems, dehydration, heart problems, medications, nutritional deficiencies, pregnancy, and septicemia and septic shock. Because there are so many different causes of hypotension, it can occur in almost anyone.
Treatment is rarely needed if hypotension does not cause any signs or symptoms. If symptoms are present, treatment depends on the underlying cause. If it is unclear what is causing symptoms of hypotension, treatment focuses on raising blood pressure. Blood pressure may be increased with diet and lifestyle changes, as well as with medications.

Related Terms

Anaphylactic shock, anaphylaxis, anemia, blood pressure, blood vessels, diastolic pressure, ECG, echo, echocardiogram, EKG, electrocardiogram, neutrally mediated hypotension, orthostatic hypotension, postprandial hypotension, postural hypotension, stress test, systolic pressure, tilt-table test, valsalva maneuver.

types of low blood pressure

Postural or orthostatic hypotension: Postural, or orthostatic, hypotension occurs when there is a sudden drop in blood pressure when a person stands up after sitting or lying down. Depending on the underlying cause, postural hypotension may be a temporary or persistent condition. Some people may only experience symptoms a few times, while others may experience long-term symptoms.
Normally, when a person stands up, the body increases its heart rate and constricts (narrows) the blood vessels. This prevents blood from pooling in the legs and ensures that the brain receives enough blood. In patients with postural hypotension, the heart rate does not increase and blood vessels do not constrict when they stand. As a result, blood pressure falls and people experience dizziness, lightheadedness, blurred vision, and sometimes fainting.
There are many possible causes of postural hypotension, including prolonged bed rest, pregnancy, dehydration, diabetes, heart problems, excessive heat, burns, large varicose veins, and some brain disorders. Several medications, including antidepressants, drugs used to treat Parkinson's disease, drugs used to treat high blood pressure, and drugs used to treat erectile dysfunction (ED), may lead to postural hypotension. Examples of these medications include beta blockers, calcium channel blockers, angiotensin-converting enzyme (ACE) inhibitors, and diuretics.
Although postural hypotension can occur in young, otherwise healthy adults, it occurs most often in older adults. In fact, as many as 20% of people older than 65 years of age have postural hypotension.
Postprandial hypotension: Postprandial hypotension refers to a sudden drop in blood pressure after eating. This type of hypotension affects older adults almost exclusively.
After eating, an increased amount of blood flows to the digestive tract. Normally, the body increases its heart rate and constricts certain blood vessels in order to maintain regular blood pressure. This process does not work properly in patients with postprandial hypotension. Because their blood vessels do not constrict, people may feel dizzy or lightheaded after eating. Symptoms may even cause some people to fall or faint.
Postprandial hypotension is most likely to occur in people who have high blood pressure because increased blood pressure may damage the blood vessels. It is also common among people with nervous system disorders such as Parkinson's disease. Nervous system disorders may prevent the brain from signaling the blood vessels to constrict properly.
Neurally mediated hypotension: Neurally mediated hypotension occurs when there is a miscommunication between the brain and the heart. This type of hypotension occurs after standing relatively stationary for extended periods of time.
This condition is caused by faulty nerves in the heart that do not communicate properly with the brain. After standing for a long time, blood starts to pool in the legs. Normally, a person's body increases blood pressure in order to ensure that the brain receives enough blood. In people with neurally mediated hypotension, the nerves in the heart signal the brain that the blood pressure is too high, rather than too low. As a result, the brain decreases the heart rate, which reduces the blood pressure even more. More blood pools in the legs and less blood reaches the brain. This causes symptoms of dizziness, lightheadedness, and sometimes fainting.
Studies have shown that neutrally mediated hypotension is often a symptom of chronic fatigue syndrome (CFS). For unknown reasons, neurally mediated hypotension occurs most often in young people.
Multiple system atrophy with orthostatic hypotension: Some people experience multiple system atrophy with orthostatic hypotension, also called Shy-Drager syndrome. This is a rare type of hypotension that leads to progressive damage to the autonomic nervous system, which controls involuntary functions, such as blood pressure, breathing, digestion, and heart rate. Parts of the brain that control these function slowly deteriorate and shrink.
Researchers have not discovered what causes the nervous system damage in patients with this type of hypotension. It has been suggested, but not proven, that it may be inherited.
This type of hypotension is characterized by severe orthostatic hypotension along with very high blood pressure when lying down. Additional symptoms may include slowed movements, decreased coordination, problems with speech, muscle tremors, and urinary incontinence.
There is currently no cure or effective treatment for this type of hypotension. Most patients die from the condition seven to 10 years after they are diagnosed.