CHAPTER 55
Low Blood Pressure
Low blood pressure (hypotension) is blood pressure low enough to cause symptoms such as dizziness and fainting.
Various drugs and disorders can cause the body’s system for maintaining blood pressure to malfunction.
When blood pressure is too low, the brain malfunctions and fainting may occur.
Normally, the body maintains the pressure of blood in the arteries within a narrow range. If blood pressure is too high, it can damage a blood vessel and even rupture it, causing bleeding or other complications. If blood pressure is too low, not enough blood reaches all parts of the body. As a result, cells do not receive enough oxygen and nutrients, and waste products are not adequately removed. Very low blood pressure can be life threatening because it can lead to shock (see page 350). Healthy people who have blood pressure that is low but still in the normal range (when measured at rest) tend to live longer than people who have higher normal blood pressure.
The body has several compensatory mechanisms that control blood pressure (see page 334). They involve changing the diameter of veins and small arteries (arterioles), the amount of blood pumped from the heart (cardiac output), and the volume of blood in the blood vessels. These mechanisms return blood pressure to normal after it increases or decreases during normal activities, such as exercise or sleep.
Veins can widen (dilate) and narrow (constrict) to change how much blood they can hold (capacity). When veins constrict, their capacity to hold blood is reduced, allowing more blood to return to the heart from which it is pumped into the arteries. As a result, blood pressure increases. Conversely, when veins dilate, their capacity to hold blood is increased, allowing less blood to return to the heart. As a result, blood pressure decreases.
Arterioles can also dilate and constrict. The more constricted arterioles are, the greater their resistance to blood flow and the higher the blood pressure. Constriction of arterioles increases blood pressure because more pressure is needed to force blood through the narrower space. Conversely, dilation of arterioles reduces resistance to blood flow, thus reducing blood pressure.
The more blood pumped from the heart per minute (that is, the larger the cardiac output), the higher the blood pressure—as long as resistance to blood flow in the arteries remains constant. The body can change the amount of blood pumped during each heartbeat by making each contraction weaker or stronger.
The higher the volume of blood in the blood vessels, the higher the blood pressure—as long as resistance to blood flow in the arteries remains constant. To increase or decrease blood volume, the kidneys can vary the amount of fluid excreted in urine.
The compensatory mechanisms are activated by specialized cells that act as sensors, called baroreceptors. Located within arteries, these sensors constantly monitor blood pressure. Those in the large arteries of the neck and chest are particularly important. When sensors detect a change in blood pressure, they trigger a change in one of the compensatory mechanisms and so maintain a steady blood pressure. Nerves carry signals from these sensors and the brain to several key organs, which control the compensatory mechanisms:
The heart is signaled to change the rate and force of heartbeats (thus changing the amount of blood pumped). This change is one of the first, and it corrects low blood pressure quickly.
The arterioles are signaled to constrict or dilate (thus changing the resistance of blood vessels).
The veins are signaled to constrict or dilate (thus changing their capacity to hold blood).
The kidneys are signaled to change the amount of fluid excreted (thus changing the volume of blood in blood vessels). This change takes a long time to produce results and thus is the slowest mechanism for blood pressure control.
For example, when a person is bleeding, blood volume and thus blood pressure decrease. In such cases, sensors activate the compensatory mechanisms to prevent blood pressure from decreasing too much: The heart rate increases, increasing the amount of blood pumped; the veins constrict, reducing their capacity to hold blood; and the arterioles constrict, increasing their resistance to blood flow. If the bleeding is stopped, fluids from the rest of the body move into the blood vessels to begin restoring blood volume and thus blood pressure. The kidneys decrease their production of urine. Thus, they help the body retain as much fluid as possible to return to the blood vessels. Eventually, the bone marrow and spleen produce new blood cells, and blood volume is fully restored.
Nonetheless, these compensatory mechanisms have limitations. For example, if a person loses a lot of blood quickly, these mechanisms cannot compensate quickly enough, blood pressure falls, and organs may begin to malfunction (shock).
Causes
Various disorders and drugs can cause the compensatory mechanisms to malfunction, and low blood pressure may result. For example, cardiac output may be reduced as a result of heart disease, such as a heart attack (myocardial infarction), a heart valve disorder, an extremely rapid heartbeat (tachycardia), a very slow heartbeat (bradycardia), or another abnormal heart rhythm (arrhythmia). These disorders impair the heart’s pumping ability. Arterioles may be dilated by toxins produced by bacteria during a bacterial infection. Blood volume can be reduced as a result of dehydration, bleeding, or kidney disorders. Some kidney disorders impair the kidneys’ ability to return fluid to the blood vessels, resulting in the loss of large amounts of fluid in the urine. (Conversely, kidney failure, in which the kidneys cannot remove fluid from the blood, may result in overhydration that leads to high blood pressure.) The ability of the nerves to conduct signals between sensors and the organs that control the compensatory mechanisms may be impaired by neurologic disorders (a condition called autonomic nervous system failure). In addition, as people age, compensatory mechanisms respond to changes in blood pressure more slowly.
Symptoms
When blood pressure is too low, the first organ to malfunction is usually the brain. The brain malfunctions first because it is located at the top of the body and blood flow must fight gravity to reach the brain. Consequently, most people with low blood pressure feel dizzy or light-headed, particularly when they stand, and some may even faint. People who faint fall to the floor, usually bringing the brain to the level of the heart. As a result, blood can flow to the brain without having to fight gravity, and blood flow to the brain increases, helping protect it from injury. However, if blood pressure is low enough, brain damage can still occur.
Low blood pressure occasionally causes shortness of breath or chest pain due to an inadequate blood supply to the heart muscle (angina).
All organs begin to malfunction if blood pressure becomes sufficiently low and remains low. This condition is called shock (see page 350).
The disorder causing low blood pressure may produce many other symptoms, which are not due to low blood pressure itself. For example, an infection may produce a fever.
Some symptoms occur when the body’s compensatory mechanisms try to increase blood pressure that is low. For example, when arterioles constrict, blood flow to the skin, feet, and hands decreases. These areas may become cold and turn blue. When the heart beats more quickly and more forcefully, a person may feel palpitations (awareness of heartbeats).
Fainting
Fainting (syncope) is a sudden, brief loss of consciousness.
Fainting occurs if brain function is disturbed.
Dizziness and light-headedness are common, but other symptoms can occur depending on the cause of fainting.
Doctors may use tilt-table testing and tests of heart function to try to determine the cause of fainting.
Usually, lying flat causes the person to regain consciousness, but underlying disorders may need to be treated.
Fainting is a symptom of an inadequate supply of oxygen and other nutrients to the brain, usually caused by a temporary decrease in blood flow. Blood flow to the brain can decrease whenever the body cannot quickly compensate for a fall in blood pressure.
SOME CAUSES OF LOW BLOOD PRESSURE
| CHANGE IN COMPENSATORY MECHANISM | CAUSES |
| Decrease in cardiac output | Abnormal heart rhythms Heart muscle damage or malfunction (such as that due to a heart attack or viral infection) Heart valve disorders Pulmonary embolism |
| Dilation of blood vessels | Alcohol Some allergic reactions Some antidepressants, such as amitriptyline Antihypertensive drugs that dilate blood vessels (such as calcium channel blockers, angiotensin-converting enzyme inhibitors, and angiotensin II receptor blockers) Nitrates Bacterial infections Exposure to heat Nerve damage (such as that due to diabetes, amyloidosis, or spinal cord injuries) |
| Decrease in blood volume | Diarrhea Diuretics (such as furosemide and hydrochlorothiazide) Excessive bleeding Excessive sweating Excessive urination (a common symptom of untreated diabetes or Addison’s disease) |
| Blockage of blood flow back to the heart | During pregnancy, pressure on the inferior vena cava (the main vein that carries blood from the legs) from the uterus when women lie in certain positions Increased abdominal pressure when straining to move bowels or pass urine or when lifting heavy weights |
| Inhibition of the brain centers that control blood pressure | Alcohol Antidepressants Antihypertensive drugs such as methyldopa and clonidine Barbiturates |
| Impairment of the autonomic nervous system | Amyloidosis Diabetes Multiple system atrophy (Shy-Drager syndrome) Parkinson’s disease |
Causes
A person cannot lose consciousness unless there is a general disturbance of brain function. This disturbance usually involves a reduction in blood flow to the brain. Blood flow to the brain can be reduced by a heart disorder or, more commonly, by something that interferes with the normal return of blood to the heart, which necessarily reduces blood flow to the brain (and the rest of the body). Rarely, blood flow to the brain is reduced by a disorder of the blood vessels at the base of the brain. Although seizures—a brain disorder—can cause loss of consciousness, they are not considered fainting. People and their doctors may not be able to differentiate between fainting and seizures without careful testing.
Problems With the Heart’s Pumping: Fainting may occur if the heart cannot pump enough blood to maintain a normal blood pressure. For example, an abnormal heart rhythm or a heart valve disorder may impair the heart’s pumping ability. People with such disorders may feel fine when resting. However, they feel faint or actually faint when exercising because the heart cannot pump enough blood to meet the body’s increased demand for oxygen. This type of fainting is called exertional or effort syncope. People with these disorders may also faint after exercising. During exercise, the increase in heart rate may enable the heart to pump enough blood to maintain adequate blood pressure, although just barely. When exercise stops, the heart rate (and the amount of blood pumped) begins to decrease. However, the blood vessels in muscles, which dilate (widen) during exercise to move more blood to and from the muscles, remain dilated. (The arterioles in muscles remain dilated to help supply oxygen and nutrients to muscle tissue, and the veins remain dilated to remove metabolic waste products produced during exercise.) The decrease in the amount of blood pumped out combined with dilation of the arterioles and veins causes blood pressure to fall, and fainting results.
An abnormality of the heart called hypertrophic cardiomyopathy (see page 363) can also cause fainting that usually occurs during exercise. Severe narrowing (stenosis) of the aortic valve can have the same effect. These disorders may occur in younger people as well as older people, particularly those who have high blood pressure. If untreated, they can lead to death.
Low Volume of Blood: Fainting may occur if the blood volume is too low. An obvious cause of low blood volume is bleeding. Another cause is dehydration, which may be due to diarrhea, excessive sweating, inadequate intake of fluids, or excessive urination (which is a common symptom of untreated diabetes—see page 1005—or Addison’s disease—see page 999). In older people, the use of diuretics is a common cause of dehydration, particularly during warm weather or during an illness when obtaining or drinking enough fluids may be difficult. (Diuretics help the kidneys eliminate salt and water by increasing urine formation and thus decrease fluid volume in the body.)
Vagus Nerve Stimulation: Fainting may occur if the vagus nerve, which supplies the neck, chest, and intestine, is stimulated. When stimulated, the vagus nerve slows the heart. Such stimulation also causes nausea and cool, clammy skin. This type of fainting is called vasovagal (vasomotor) syncope. The vagus nerve is stimulated by pain, fear, other distress (such as that due to the sight of blood), vomiting, a large bowel movement, and urination. Fainting during or immediately after urination is called micturition syncope. Rarely, vigorous swallowing causes fainting due to stimulation of the vagus nerve.
Reduced Blood Flow: Fainting may also occur if straining reduces the amount of blood flowing back to the heart. Fainting due to coughing (cough syncope) usually results from such straining. Fainting after urination (micturition syncope) or after a bowel movement is partly due to straining (in addition to stimulation of the vagus nerve). Older men who must strain to empty their bladder because of a large prostate gland are particularly susceptible. Fainting when lifting weights (weight lifter’s syncope) results from the strain of trying to lift or push heavy weights without breathing adequately during the exercise.
Problems With Blood Pressure: Fainting that occurs when a person sits or stands up too quickly is called orthostatic (postural) syncope. It is particularly common among older people. It is caused by orthostatic hypotension (see page 348). In orthostatic hypotension, the compensatory mechanisms, particularly the constriction of blood vessels and the increase in heart rate, do not adequately restore blood pressure when a person stands and gravity causes blood to pool in the leg veins. A related form of fainting, called parade ground syncope, occurs when people stand still for a long time on a hot day. If the leg muscles are not used, blood is not pumped back to the heart. As a result, blood pools in the leg veins, and blood pressure falls.
In older people, an excessive decrease in blood pressure after eating a meal (postprandial hypotension—see page 349) may cause fainting.
Other Problems: Fainting may result from very rapid breathing (hyperventilation, or overbreathing), which may be due to anxiety. This type of fainting is called hyperventilation syncope. Hyperventilation removes large amounts of carbon dioxide from the body. The decreased level of carbon dioxide causes blood vessels in the brain to constrict, and the person may feel faint or actually faint.
Rarely, fainting results from a mild stroke in which blood flow to a certain part of the brain (at the base) suddenly decreases. Fainting due to a stroke is more common among older people. Many other disorders, such as a deficiency of red blood cells (anemia), lung disorders, a decreased blood sugar level (hypoglycemia), and diabetes can cause fainting, especially if the compensatory mechanisms are also impaired.
Certain drugs may cause fainting. They include many of those used to treat high blood pressure, angina, and heart failure. Doses of these drugs must be carefully adjusted to prevent blood pressure from decreasing too much.
Symptoms
Dizziness or light-headedness may precede fainting, especially if the person is standing. After the person falls, blood pressure increases, partly because the person is lying down (and blood can flow to the brain without having to fight gravity) and often because the cause of fainting has passed. However, getting up too quickly may make the person faint again.
When the cause is an abnormal heart rhythm (arrhythmia), fainting usually begins and ends suddenly. Sometimes the person feels palpitations (awareness of heartbeats) just before fainting.
Vasovagal syncope may occur when a person is sitting or standing. It is often preceded by nausea, weakness, yawning, blurring of vision, and sweating. The skin may become cool and clammy. The person becomes ghostly pale, the pulse becomes very slow, and the person faints.
Fainting that begins gradually with warning symptoms and also disappears gradually suggests changes in the blood, such as a decreased level of sugar (hypoglycemia) or carbon dioxide (hypocapnia). Hypocapnia is often preceded by a pins-and-needles sensation in the fingertips and around the lips.
Diagnosis
Doctors try to determine the cause of fainting because some causes are more serious than others. Heart disease, such as an abnormal heart rhythm or narrowing (stenosis) of the aortic valve, can be fatal. Other causes are much less worrisome.
Sometimes the nature of the symptoms suggests a cause to the doctor. Descriptions from witnesses of the fainting episode may be helpful. Of concern is fainting that occurs without any warning symptoms (particularly during exertion), is accompanied by shortness of breath or chest pain, results in injury, or occurs in a person with an abnormal finding during an examination of the heart or nervous system. Doctors also need to know whether the person has any disorders and whether the person is taking any prescription or over-the-counter drugs.
If the fainting occurs during emotionally stressful situations or is preceded by symptoms of vasovagal syncope (such as nausea, sweating, cool and clammy skin, and paleness), fainting usually is not serious, and extensive diagnostic procedures and treatment are rarely necessary.
Doctors will often obtain an electrocardiogram (ECG), which records the electrical activity of the heart and can detect an underlying heart disorder. Continuous ECG may be required to determine the cause of fainting. For this procedure, the person wears a small battery-powered device (Holter monitor). It records the heart’s electrical activity for 24 hours or more as the person engages in normal daily activities (see page 327). If an irregular heart rhythm coincides with a fainting episode, it is probably—but not necessarily—the cause.
Other procedures, such as echocardiography, which uses ultrasound waves to produce an image of the heart (see page 328), can detect whether the heart has a structural or functional abnormality. Blood tests may show that the person has hypoglycemia or anemia.
SPOTLIGHT ON AGING
Low blood pressure may be caused by many disorders that affect the heart. Because many heart disorders are common among older people, older people are also more likely to have low blood pressure.
A heart muscle that is weakened because of a heart attack can pump less blood, leading to low blood pressure. Infections, heart valve disorders, and drugs that damage the heart may also decrease the pumping ability. Pericarditis causes fluid to build up within the sac surrounding the heart (the pericardium), compressing the heart and restricting its ability to pump blood.
An abnormally slow or an abnormally fast heart rate can cause low blood pressure. If the heart rate is slow (bradycardia), the heart does not pump sufficient blood to the body. If the heart rate is fast, as happens in atrial fibrillation, the ventricles do not have time to fill completely with blood before each heartbeat and cannot pump enough blood to the body.
Some drugs, such as calcium channel blockers and angiotensin-converting enzyme inhibitors that are used to treat heart disorders, diuretics, and drugs for Parkinson’s disease, may also lower blood pressure.
Orthostatic hypotension is particularly common among older people who take drugs to treat high blood pressure. Older people are also more likely to experience low blood pressure and loss of consciousness during urination (micturition syncope) and after eating (postprandial hypotension).
The body has many mechanisms to help prevent low blood pressure, but these mechanisms work less well in older people.
Loss of consciousness due to a seizure (see page 709) is distinguished from fainting because the causes and treatment are different. To distinguish between the two, doctors may use electroencephalography (EEG), which records the brain’s electrical activity (see page 636). Also, after a seizure, recovery from unconsciousness is much slower, causing drowsiness that usually lasts for at least 10 minutes.
To confirm a suspected cause, doctors may attempt to re-create a fainting episode under safe conditions. For example, the person may be asked to breathe quickly and deeply. Or, while monitoring the heartbeat with ECG, a doctor may press gently over the carotid sinus (a part of the internal carotid artery containing sensors that monitor blood pressure). This pressure temporarily increases blood pressure inside the carotid sinus, tricking the body into thinking that blood pressure has increased throughout the body. The sinus then sends signals to the brain to reduce blood pressure, and faintness or fainting may result.
Tilt table testing (see page 328) is commonly done to determine the cause of fainting. The person is strapped to a motorized table. Then the table tilts until the person is almost standing. This position is held for up to 45 minutes. Blood pressure and heart rate are continuously monitored during the test. If blood pressure does not decrease, the person is given isoproterenol (a drug that stimulates the heart), and the test is repeated. Use of this drug makes the test more sensitive.
Treatment
Usually, lying flat restores consciousness. Raising the legs can speed recovery by increasing blood flow to the heart and brain. If the person sits up too rapidly or is propped up or carried in an upright position, another fainting episode may occur. Therefore, the person should remain lying down until fully recovered.
A heart rate that is too slow can be corrected by surgically implanting a pacemaker, an electronic device that stimulates heartbeats (see art on page 369). A heart rate that is too rapid can be slowed by using drugs, particularly a beta-blocker (such as atenolol or metoprolol). A defibrillator can be implanted to restore normal rhythm if the heart beats irregularly (see page 368). Other causes of fainting—such as hypoglycemia and anemia—can be treated. If blood volume is very low, fluids may be given intravenously. Surgery may be considered for heart valve disorders.
Orthostatic Hypotension
Orthostatic hypotension is an excessive decrease in blood pressure that occurs when a person stands up, resulting in reduced blood flow to the brain and dizziness or fainting.
Dizziness or light-headedness that occurs when a person sits up or stands abruptly is the most common symptom.
Measuring blood pressure while the person is sitting and standing may reveal orthostatic hypotension.
When the cause cannot be cured, people are taught to stand up gradually and to drink plenty of fluids.
Orthostatic hypotension is particularly common among older people.
Orthostatic hypotension is not a specific disease but an inability to compensate quickly for changes in blood pressure. When a person stands up suddenly, gravity causes about a pint of blood to pool in the veins of the legs and lower body. As a result, the amount of blood returned to the heart and pumped out by the heart is reduced, and blood pressure falls. Normally, the body quickly responds to a decrease in blood pressure: The heart beats faster and more forcefully to increase its output of blood and the arterioles (small arteries) constrict to increase resistance to blood flow (see page 343). If these compensatory mechanisms malfunction or function too slowly—both of which commonly occur in older people—orthostatic hypotension may occur.
Causes
Orthostatic hypotension is caused by conditions that interfere with the compensatory mechanisms that control blood pressure. These conditions include many disorders and drugs as well as normal age-related changes.
Some conditions cause orthostatic hypotension by affecting the heart’s ability to increase its output enough when a person stands. This problem can be caused by heart disease, such as abnormal heart rhythms and heart valve disorders. Also, with aging, the body becomes less able to increase the heart rate (and thus the heart’s output) when a person stands.
Some conditions cause orthostatic hypotension by reducing blood volume. Diuretics, which are used to treat high blood pressure, can reduce blood volume by removing fluid from the body. Diuretics, especially potent ones given in high doses, are a common cause of orthostatic hypotension. Other causes of reduced blood volume include bleeding and an excessive loss of fluid due to severe vomiting, diarrhea, excessive sweating, or excessive urination (which is a common symptom of untreated diabetes or Addison’s disease). Among older people, dehydration during an illness is a common cause of low blood volume leading to orthostatic hypotension. People who are ill may not be able to obtain fluids without assistance. Also, during an illness, the leg muscles are not used regularly. As a result, blood pools in the leg veins and is not pumped back to the heart (see page 433). Because this pooling reduces the amount of blood returning to the heart, it, in effect, reduces blood volume and thus reduces blood pressure.
Some conditions cause orthostatic hypotension by dilating arterioles and veins. Drugs that dilate arterioles (vasodilators) can cause orthostatic hypotension. They include nitrates, calcium channel blockers, angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers, alpha blockers, alcohol, and antidepressants. Disorders such as diabetes, amyloidosis, and spinal cord injuries may damage the nerves that regulate blood vessel diameter. In addition, veins dilate when body temperature increases, for example, because of a warm day, a warm room, or too much clothing. Fever also has this effect.
Fatigue, exercise (which causes blood vessels to dilate), or consumption of a heavy meal (which requires increased blood flow to the intestine) can contribute to orthostatic hypotension.
Symptoms and Diagnosis
Most people with orthostatic hypotension experience some faintness, light-headedness, dizziness, confusion, or blurred vision when they get out of bed abruptly or stand up after sitting for a long time. Symptoms are worse if people are tired, have been exercising, have consumed alcohol, or have eaten a heavy meal. A severe decrease in blood flow to the brain can cause the person to faint and even to have seizures.
These symptoms suggest orthostatic hypotension. The diagnosis can be confirmed if the blood pressure falls significantly when the person stands and returns to normal when the person lies down. Doctors then look for the cause of orthostatic hypotension, because treatment and prognosis depend on the cause.
Treatment
Even when the cause of orthostatic hypotension cannot be treated, certain measures can often reduce or eliminate symptoms. For example, susceptible people should not sit or stand up rapidly or remain standing still for long periods. They should sit or stand up slowly. Wearing fitted elastic stockings up to the waist may help reduce pooling of blood in the leg veins. If orthostatic hypotension results from prolonged bed rest, gradually increasing the time spent sitting up each day may help.
Several measures help maintain blood volume. People with orthostatic hypotension should drink plenty of fluids and little or no alcohol. People who do not have heart failure or high blood pressure are often told to salt their food liberally or to take salt tablets. However, a doctor’s supervision is necessary, because a high-salt diet can lead to heart failure in certain people, particularly older people. For people who have severe symptoms, taking hormones that cause salt to be retained, such as fludrocortisone, can increase blood volume. However, use of such hormones increases the risk of heart failure, particularly for older people and people who have heart disease. Use of fludrocortisone can also cause a loss of potassium, so taking a potassium supplement may be necessary. Midodrine may be taken with fludrocortisone to help prevent blood pressure from falling. Midodrine constricts arterioles, thereby reducing their capacity to hold blood and increasing resistance to blood flow.
If these measures are ineffective, other drugs (such as pindolol and clonidine), which work in various ways, may help relieve orthostatic hypotension in certain people. However, the risk of side effects from these drugs may make their use undesirable, particularly by older people.
Postprandial Hypotension
Postprandial hypotension is an excessive decrease in blood pressure that occurs after a meal.
Dizziness, light-headedness, and falls may occur.
Doctors measure blood pressure before and after a meal to diagnose postprandial hypertension.
Eating small, low-carbohydrate meals frequently may help.
Postprandial hypotension occurs in up to one third of older people but virtually never occurs in younger people. It is more likely to occur in people who have high blood pressure or disorders that impair the brain centers controlling the autonomic nervous system (which regulates internal body processes). Examples of such disorders are Parkinson’s disease, multiple system atrophy (Shy-Drager syndrome), and diabetes.
The intestine requires a large amount of blood for digestion. When blood flows to the intestine after a meal, the heart rate increases and blood vessels in other parts of the body constrict to help maintain blood pressure. However, in some older people, such mechanisms may be inadequate. Blood flows normally to the intestine, but the heart rate does not increase adequately and blood vessels do not constrict enough to maintain blood pressure. As a result, blood pressure falls.
Postprandial hypotension can cause dizziness, light-headedness, faintness, and falls. If an older person experiences these symptoms after eating, doctors measure blood pressure before and after meals to determine if postprandial hypotension is the cause.
People who have symptoms of postprandial hypotension should not take antihypertensive drugs before meals and should lie down after meals. Taking a smaller dose of the antihypertensive drugs and eating small, low-carbohydrate meals more frequently may help reduce the effects of this disorder. For some people, walking after a meal helps improve blood flow, but blood pressure may fall when they stop walking.
Taking certain drugs before a meal may help. For example, nonsteroidal anti-inflammatory drugs (NSAIDs) cause salt to be retained and thus increase blood volume. Caffeine causes blood vessels to constrict. Caffeine should be taken only before breakfast so that sleep is not affected and the person does not become tolerant of caffeine’s effects. For people who have severe symptoms that do not respond to other measures and who are in the hospital, injections of the drug octreotide may help by reducing the amount of blood flowing to the intestine.