Low blood pressure (hypotension) would seem to be something to strive for. However, for many people, low blood pressure can cause symptoms of dizziness and fainting. In severe cases, low blood pressure can be life-threatening.
Although blood pressure varies from person to person, a blood pressure reading of 90 millimeters of mercury (mm Hg) or less systolic blood pressure (the top number in a blood pressure reading) or 60 mm Hg or less diastolic blood pressure (the bottom number) is generally considered low blood pressure.
The causes of low blood pressure can range from dehydration to serious medical or surgical disorders. Low blood pressure is treatable, but it’s important to find out what’s causing your condition so that it can be properly treated.
Everyone’s blood pressure drops at one time or another, often without adverse reaction. Certain conditions can cause prolonged period of hypotension that can become dangerous if left untreated. These include:
- pregnancy (due to an increase in demand for blood from both mother and the growing fetus)
- large amounts of blood loss through injury
- impaired circulation caused by heart attacks or faulty heart valves
- weakness and a state of shock that sometimes accompany dehydration
- anaphylactic shock, a severe form of allergic reaction
- infections of the bloodstream
- endocrine disorders such as diabetes, adrenal insufficiency, and thyroid disease
Medications might also cause a drop in blood pressure. Beta-blockers and nitroglycerin, used to treat heart disease, are common culprits. Diuretics, tricyclic antidepressants, and erectile dysfunction drugs can also cause hypotension.
Some people have low blood pressure for unknown reasons. This form of hypotension, called chronic asymptomatic hypotension, usually does not cause harm.
Studies on the incidence and pathophysiology of hypotension in fulminant hepatic failure showed that 82 out of 94 patients developed arterial hypotension with a systolic blood pressure of less than 80 mmHg. Such episodes accounted for 16% of the total time spent in grade IV coma. Factors such as haemorrhage, cardiac or respiratory abnormalities, extracorporeal perfusion, or hypotension which occurred during the terminal stages of the illness, could be implicated for only 40% of this time, leaving 60% as unexplained. Further investigation of these unexplained factors showed that peripheral vasodilatation rather than primary heart failure was responsible, and in all but three patients construction of ventricular function curves showed a normal ventricular response to volume expansion with a corresponding increase in blood pressure. A small, but significant, slowing of the heart rate occurred during these periods of unexplained hypotension. This, together with the association that was found between the occurrence of hypotension and cerebral oedema with coning, suggests that central vasomotor depression may be important in its pathogenesis.
- Dimming or blurring of vision
- Cold, clammy skin
- Pale skin
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
A primary care doctor or specialist may diagnose and treat hypotension. The type of specialist most commonly involved is a cardiologist (heart specialist).
Other specialists also may be involved, such as surgeons, nephrologists (kidney specialists), or neurologists (brain and nerve specialists).
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.
During a blood test, a small amount of blood is taken from your body. It’s usually drawn from a vein in your arm using a needle. The procedure is quick and easy, although it may cause some short-term discomfort.
Blood tests can show whether anemia or low blood sugar is causing your hypotension.
An EKG is a simple test that detects and records your heart’s electrical activity. It shows how fast your heart is beating and whether its rhythm is steady or irregular. An EKG also shows the strength and timing of electrical signals as they pass through each part of your heart.
Holter and Event Monitors
Holter and event monitors are medical devices that record your heart’s electrical activity. These monitors are similar to an EKG. However, a standard EKG only records your heartbeat for a few seconds. It won’t detect heart rhythm problems that don’t occur during the test.
Holter and event monitors are small, portable devices. You can wear one while you do your normal daily activities. This allows the monitor to record your heart for longer periods than a standard EKG.
Echocardiography (echo) is a test that uses sound waves to create a moving picture of your heart. The picture shows how well your heart is working and its size and shape.
There are several types of echo, including stress echo. This test is done as part of a stress test (see below). Stress echo usually is done to find out whether you have decreased blood flow to your heart, a sign of coronary heart disease (also called coronary artery disease).
Some heart problems are easier to diagnose when your heart is working hard and beating fast. During stress testing, you exercise (or are given medicine if you’re unable to exercise) to make your heart work hard and beat fast while heart tests are done.
These tests may include nuclear heart scanning, echo, and positron emission tomography (PET) scanning of the heart.
This is a simple test for the part of your nervous system that controls functions such as your heartbeat and the narrowing and widening of your blood vessels. If something goes wrong with this part of the nervous system, blood pressure problems may occur.
During this test, you take a deep breath and then force the air out through your lips. You will do this several times. Your heart rate and blood pressure will be checked during the test.
Low blood pressure that either doesn’t cause signs or symptoms or causes only mild symptoms, such as brief episodes of dizziness when standing, rarely requires treatment.
If you have symptoms, the most appropriate treatment depends on the underlying cause, and doctors usually try to address the primary health problem — dehydration, heart failure, diabetes or hypothyroidism, for example — rather than the low blood pressure itself.
When low blood pressure is caused by medications, treatment usually involves changing the dose of the medication or stopping it entirely.
If it’s not clear what’s causing low blood pressure or no effective treatment exists, the goal is to raise your blood pressure and reduce signs and symptoms. Depending on your age, health status and the type of low blood pressure you have, you can do this in several ways:
- Use more salt. Experts usually recommend limiting the amount of salt in your diet because sodium can raise blood pressure, sometimes dramatically. For people with low blood pressure, that can be a good thing.
But because excess sodium can lead to heart failure, especially in older adults, it’s important to check with your doctor before increasing the salt in your diet.
- Drink more water. Although nearly everyone can benefit from drinking enough water, this is especially true if you have low blood pressure.
Fluids increase blood volume and help prevent dehydration, both of which are important in treating hypotension.
- Wear compression stockings. The same elastic stockings commonly used to relieve the pain and swelling of varicose veins may help reduce the pooling of blood in your legs.
- Medications. Several medications, either used alone or together, can be used to treat low blood pressure that occurs when you stand up (orthostatic hypotension).
For example, the drug fludrocortisone is often used to treat this form of low blood pressure. This drug helps boost your blood volume, which raises blood pressure.
Doctors often use the drug midodrine (Orvaten) to raise standing blood pressure levels in people with chronic orthostatic hypotension. It works by restricting the ability of your blood vessels to expand, which raises blood pressure.