Subnormal arterial blood pressure. Hypotension is the medical term for low blood pressure.
Other Names: Low blood pressure, postprandial hypotension, orthostatic hypotension, and neurally mediated hypotension (NMH)
Types: Arterial hypotension, idiopathic orthostatic hypotension, induced hypotension, intracranial hypotension, orthostatic hypotension, and postural hypotension.
The heart is a muscle that pumps blood around the body continuously. Blood that is low in oxygen is pumped towards the lungs, where oxygen supplies are replenished. The heart pumps this oxygen-rich blood around the body to supply our muscles and cells. The pumping of blood generates pressure - blood pressure.
When we measure blood pressure, we gauge two different types of pressure:
Systolic pressure - the blood pressure when the heart contracts, specifically the moment of maximum force of the contraction, which occurs when the left ventricle of the heart contracts.
Diastolic pressure - the blood pressure between heartbeats, when the heart is resting and opening up, (dilating).
Normal blood pressure in adults is around 120/80 mmHg. Hypotension is blood pressure that's lower than 90/60 mmHg.
There are several types of hypotension. One type, chronic asymptomatic hypotension, happens in people who always have low blood pressure. They have no symptoms and need no treatment. Their low blood pressure is normal for them.
Other types of hypotension happen only sometimes, when blood pressure suddenly drops too low. The symptoms and effects on the body can be mild or severe. The three main types of this kind of hypotension are orthostatic hypotension, neurally mediated hypotension (NMH), and severe hypotension associated with shock.
Acute: Acute hypotension is a sudden drop in your BP that may be life-threatening. With acute hypotension, your SBP drops below 90 millimeters of mercury (mmHg), or your SBP drops 40 mmHg or more.
Constitutional: Constitutional hypotension means your BP is lower than it should be most or all of the time. Constitutional hypotension is a chronic (long-term) condition that occurs with no known medical cause. For men with constitutional hypotension, the SBP is lower than 110 mmHg. For women, the SBP is lower than 100 mmHg.
Orthostatic: Orthostatic hypotension (OH) occurs when your BP drops as you change positions. OH is also called postural hypotension. OH normally occurs when you stand up from a sitting or lying position. With OH, your SBP drops at least 20 mmHg, or your DBP drops at least 10 mmHg. Your BP may drop right after standing, or within three minutes of standing. If your BP drops after you have been standing for more than three minutes, you may have delayed OH.
Postprandial: Postprandial (after eating) hypotension means your BP becomes too low after eating a meal. Your BP may drop within two hours after eating, and is more common when eating meals high in carbohydrates. Carbohydrates are found in starchy foods, such as potatoes and foods with sugar. With postprandial hypotension, your SBP drops at least 20 mmHg, or your SBP drops lower than 90 mmHg.
Symptoms include: Blurry vision
, confusion, dizziness
, fainting (syncope), and lightheadedness, sleepiness, and weakness.
Other symptoms include excessive transpiration, palpitations, tingling sensation, cold, pallor, and sexual inappetence. Low blood pleasure can even cause shortness of breath and chest pain.
Causes and Risk Factors:
Causes of low blood pressure due to low blood volume
Dehydration: Moderate to severe dehydration may cause orthostatic hypotension (manifest by light-headedness, dizziness or fainting upon standing). Protracted and severe dehydration can lead to shock, kidney failure, confusion, acidosis (too much acid in the blood), coma, and even death.
- Moderate or severe bleeding can quickly deplete an individual's body of blood, leading to low blood pressure or orthostatic hypotension.
- Severe inflammation of organs inside the body such as acute pancreatitis can cause low blood pressure. In acute pancreatitis, fluid leaves the blood to enter the inflamed tissues around the pancreas as well as the abdominal cavity, depleting the volume of blood.
Causes of low blood pressure due to heart disease
Weakened heart muscle can cause the heart to fail and reduce the amount of blood it pumps. One common cause of weakened heart muscle is the death of a large portion of the heart's muscle due to a single, large heart attack or repeated smaller heart attacks.
- Pulmonary embolism is a condition in which a blood clot in a vein (a condition called deep vein thrombosis) breaks off and travels to the heart and eventually the lung. A large blood clot can block the flow of blood into the left ventricle from the lungs and severely diminish the ability of the heart to pump blood.
- A slow heart rate (bradycardia) can decrease the amount of blood pumped by the heart. The resting heart rate for a healthy adult is between 60 and 100 beats/minute. Bradycardia (resting heart rates slower than 60 beats/minute) does not always cause low blood pressure. But in many patients bradycardia can lead to low blood pressure, light-headedness, dizziness, and even fainting.
- An abnormally fast heart rate (tachycardia) also can cause low blood pressure. The most common example of tachycardia causing low blood pressure is atrial fibrillation. Atrial fibrillation is a disorder of the heart characterized by rapid and irregular electrical discharges from the muscle of the heart (instead of the SA node), causing the ventricles to contract irregularly and (usually) rapidly. The rapidly contracting ventricles do not have enough time to fill maximally with blood before the each contraction, and the amount of blood that is pumped decreases, in spite of the faster heart rate.
- Side effects from certain medications, especially diuretics or other high blood pressure medications, like beta blockers. Medicines used to treat erectile dysfunction and certain psychiatric disorders can also cause low blood pressure.
Some medications you may take can also cause low blood pressure, including:
- Beta blockers.
- Drugs for Parkinson's disease.
- Tricyclic antidepressants.
- Sildenafil particularly in combination with another heart medication, nitroglycerine.
Hormone problems such as adrenal insufficiency or thyroid disease (overactive or underactive thyroid).
- Problems with the nervous system especially disorders of the autonomic nervous system, including POTS and vasovagal syncope can cause low blood pressure after extended periods of standing.
- Deficiencies of essential nutrients, such as folic acid, can cause the number of red blood cells to decrease (anemia) and cause hypotension.
Age. Orthostatic hypotension most often occurs in the elderly.
- Alcohol and drug abuse: Drinking too much alcohol, too often, may increase your risk for hypotension. Using street drugs, such as marijuana, may also increase your risk for hypotension.
- Low body weight: Weighing less than you should for your height increases your risk for hypotension.
- Hemodialysis: Hemodialysis treatments remove extra fluid from your body when you have kidney failure. If too much fluid is removed from your body, your blood pressure may drop lower than it should.
- Medical problems: Diseases, such as diabetes, Parkinson's disease, and Alzheimer's disease, increase your risk for ANS problems and hypotension.
As the hypotension is related to many underlying problems, the goal in testing for low blood pressure is to find the underlying cause. This helps determine the correct treatment and identify any heart, brain or nervous system problems that may cause lower than normal readings. To reach a diagnosis your doctor may recommend one or more of the following tests:
Blood Tests: These can provide information about your overall health as well as whether you have low blood sugar (hypoglycemia), high blood sugar (hyperglycemia or diabetes) or a low number of red blood cells (anemia), all of which can cause lower than normal blood pressure.
Echocardiogram: This noninvasive exam, which includes an ultrasound of your chest, shows detailed images of your heart's structure and function. Ultrasound waves are transmitted, and their echoes are recorded with a device called a transducer that's held outside your body. A computer uses the information from the transducer to create moving images on a video monitor.
Electrocardiogram (ECG): This noninvasive test which detects irregularities in your heart rhythm, structural abnormalities in your heart, and problems with the supply of blood and oxygen to your heart muscle.
Stress test: Some heart problems that can cause low blood pressure are easier to diagnose when your heart is working harder than when it's at rest. During a stress test, you'll exercise, such as walking on a treadmill. You may be given medication to make your heart work harder if you're unable to exercise. When your heart is working harder, your heart will be monitored with electrocardiography or echocardiography. Your blood pressure also may be monitored.
Valsalva maneuver: This noninvasive test checks the functioning of your autonomic nervous system by analyzing your heart rate and blood pressure after several cycles of a type of deep breathing. You take a deep breath and then force the air out through your lips, as if you were trying to blow up a stiff balloon.
Tilt table test: If you have low blood pressure on standing, or from faulty brain signals your doctor may suggest a tilt table test, which evaluates how your body reacts to changes in position. During the test, you lie on a table that's tilted to raise the upper part of your body, which simulates the movement from horizontal to a standing position.
Treatment depends on the type of hypotension you have and how severe your signs and symptoms are. The goals of treatment are to relieve signs and symptoms and manage any underlying conditions causing the hypotension.
If you have symptoms, the best 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, 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 by following ways:
Drinking plenty of fluids, like water.
- Drinking little or no alcohol.
- Standing up slowly.
- Not crossing your legs while sitting.
- Gradually sitting up for longer periods if you've been immobile for a long time due to a medical condition.
- Eating small, low-carbohydrate meals if you have postprandial hypotension.
Those with NMH (neurally mediated hypotension) should avoid triggers, such as standing for a long period of time. Other treatments involve drinking plenty of fluids and increasing the amount of salt in your diet. In severe cases, medicines such as fludrocortisone may be prescribed.
Your response to treatment depends on your age, overall health, and strength. It also depends on how easily you can stop, start, or change medicines.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.