Blood pressure and hypertension

Blood pressure is a measurement that reflects the amount of force exerted by the blood on the artery walls as it's pumped from the heart and through the circulatory system.

The upper blood pressure reading (systolic) indicates the pressure within the arteries as the heart pumps blood out of the ventricles (the pumping chambers of the heart). The lower reading (diastolic) indicates the pressure within the arteries when the heart is resting between beats. Because the systolic reading represents the moment of greater pressure, systolic blood pressure is always higher than diastolic blood pressure.


Understanding high blood pressure
Adequate blood pressure is needed to provide blood flow to the major organs and other structures of the body. High blood pressure or hypertension, however, can be a major health concern. It's characterized by an increased resistance to blood flow within the blood vessels. This increased resistance requires the heart to work harder to pump blood. It also damages the arteries and organs they feed. Because there are typically no symptoms, high blood pressure is often referred to as the "silent killer."
Up to 95 percent of people who have high blood pressure have essential hypertension, defined as high blood pressure with no apparent cause. Secondary hypertension is the result of another medical condition. For example, kidney disease, thyroid disease and pregnancy complications can lead to secondary hypertension. In other cases, secondary hypertension is caused by certain medications, including decongestants, oral contraceptives and nicotine products. Certain narcotic drugs, such as cocaine, can also cause abrupt and severe elevation of blood pressure.

Risk factors
An estimated 50 million Americans, or roughly one in four adults, have above normal blood pressure levels. Risk factors include having a family history of hypertension, having diabetes, and being African American. Certain lifestyle factors -- such as smoking, being overweight, being largely sedentary, and consuming excess fat, sodium and alcohol -- may contribute to age-related rises in blood pressure. Perhaps the largest risk factor for developing high blood pressure, however, is age.

Important considerations
In addition to age and weight, blood pressure can vary as a result of the following factors:

Sex: From adolescence through middle age, males are more likely to have high blood pressure than females of the same age. The opposite is true later in life, however.
Time of day: Blood pressure is usually lowest just before waking in the morning.
Activity level: Strenuous activity increases blood pressure temporarily.
Psychological factors: Nervousness and anxiety can also increase blood pressure.

Understanding low blood pressure
Low blood pressure can develop with certain conditions, including endocrine or nerve disorders, volume depletion or sepsis (overwhelming infection). Prolonged bedrest may have the same effect.
Low blood pressure can also be caused by a decrease in blood volume related to hemorrhaging (heavy bleeding) or dehydration (as may occur with vomiting, diarrhea, poor fluid intake or excessive sweating).

In other cases, low blood pressure is related to treatment for high blood pressure.


Signs/symptoms
High blood pressure
Most people who have high blood pressure usually have no symptoms, even with their blood dangerously high. In some cases, people who have dangerously high blood pressure experience:

headache
fatigue or a general feeling of discomfort
lightheadedness or dizziness
shortness of breath
visual disturbances
nausea or vomiting
neurological changes (such as weakness, numbness or tingling)
confusion
chest pain
swelling
If you experience any of these symptoms, contact your doctor or seek medical attention promptly. Because high blood pressure usually has no symptoms, it's extremely important to follow through with regular, routine exams or take advantage of blood pressure screening programs.

Low blood pressure
If you're minimally active or sedentary, low blood pressure may not cause any symptoms. When blood flow to the brain and vital organs isn't adequate, symptoms may include:

lightheadedness, especially when standing
fainting
clouded or changed vision
fatigue with minimal exertion
If you experience any of these symptoms, contact your doctor or seek medical attention promptly. For most people, low blood pressure isn't considered problematic until symptoms appear. If you don't have symptoms but are concerned your blood pressure is too low, talk to your doctor.


Measuring blood pressure
To measure your blood pressure, a blood pressure cuff will be placed around your arm, just above the elbow. Then, air will be pumped into the cuff. The systolic and diastolic readings are measured through characteristic sounds heard through a stethoscope placed over the brachial artery (under the cuff) as the air is released.
Note: Blood pressure readings can vary with position, such as sitting, standing and lying down. A cuff that's too small for your arm can result in a falsely high reading.

If you monitor your blood pressure at home, the American Heart Association recommends learning proper technique from a health care professional. Then, follow these general guidelines:

Know your typical readings, as well as what your doctor considers your optimal range. Also know when your doctor wants to be notified.

Record the time of day of each reading.

Avoid smoking and consuming caffeine for at least 30 minutes before you take your blood pressure, and rest for five minutes before the reading.

Make sure your bare arm is supported at heart level and the cuff size is appropriate.

Avoid crossing your legs or moving during the reading.

Occasionally compare your home readings to those given through standard mercury equipment by taking your home equipment to follow-up appointments with your doctor.
Keep in mind that aneroid and electronic or digital readout equipment typically need to be calibrated at least once a year by a trained technician.


Diagnosis
A diagnosis of high blood pressure must be based on a series of high blood pressure readings, rather than a single measurement. Because high blood pressure often appears without symptoms, it's important to check your blood pressure on a yearly basis, especially as you age. Early detection and intervention can help you avoid complications. New guidelines published in 2003 have changed the categories of blood pressure readings, with emphasis on treating high blood pressure early and aggressively.
Blood pressure classifications for adults age 18 and older
The following blood pressure categories are based on an average of two or more readings taken during each of two or more visits after an initial screening.

Category Systolic
(mm Hg) Diastolic
(mm Hg)
Normal less than 120 and less than 80
Prehypertension 120 to 139 or 80 to 89
Stage 1 hypertension 140 to 159 or 90 to 99
Stage 2 hypertension 160 or higher 100 or higher



Source: The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7 Express). NIH publication no. 03-5233, May 2003.
Blood pressure norms for children
Blood pressure norms in children vary with sex, age and height. For example:

Normal blood pressure in children is defined as average systolic and diastolic blood pressure less than the 90th percentile for age and sex.
Prehypertensive blood pressure is blood pressure greater than or equal to the 90th percentile but less than the 95th percentile.
High blood pressure is defined as average systolic and diastolic blood pressure greater than or equal to the 95th percentile. The reading must be confirmed on at least three separate occasions.
High blood pressure is divided into two stages: stage 1 and stage 2. Stage 1 hypertension is defined as blood pressure equal to the 95th percentile and up to 5 mm/Hg greater than the 99th percentile. Stage 2 hypertension is defined as blood pressure greater than 5 mm/Hg above the 99th percentile.

The following numbers will give you an idea of the readings the National Institutes of Health (NIH) considers the upper limit of normal (90th percentile) for a child with average height (50th percentile) according to standard growth curves:


Age Systolic Diastolic
1 year 99 (boy)
100 (girl) 52 (boy)
54 (girl)
5 years 108 (boy)
106 (girl) 68 (boy)
68 (girl)
10 years 115 (boy)
115 (girl) 75 (boy)
74 (girl)
15 years 127 (boy)
123 (girl) 79 (boy)
79 (girl)


Treatment
Treatment for high blood pressure depends on your health status, age and current medication use, as well as what type of hypertension you have. For example, treatment for secondary hypertension is aimed toward the underlying cause of the hypertension. If you're considered prehypertensive, your doctor may only recommend certain lifestyle modifications. In other cases, medication is needed as well.
Treatment for low blood pressure depends on the cause. For example, it may involve adjusting any medications you take, rehydration or managing associated medical conditions.

Medication for high blood pressure in adults
Before using any medication or other product for high blood pressure, consult your doctor. Even over-the-counter products may lead to medication interactions, and you may need a prescription medication to adequately treat your condition.

The Joint National Committee (JNC) on Prevention, Detection, Evaluation and Treatment of High Blood Pressure currently recommends diuretics alone or in combination with another medication as the first line of treatment for people who have uncomplicated high blood pressure. The new guidelines report that most people will need two or more medications to lower their blood pressure to the desired level. If you also have other medical conditions -- such as diabetes, kidney disease, a history of stroke or certain heart problems -- your doctor will base your treatment on these factors.

Diuretics: Diuretics stimulate the kidneys to rid the body of excess water and sodium through urination.
Benefits: Diuretics can effectively lower blood pressure. They may also reduce the risk of having a heart attack or stroke.

Risks: Taking certain diuretics may lead to potassium imbalance, which may cause irregular heart rhythms. Diuretics may make you feel thirsty, and you'll need to urinate more often. Diuretics may also cause attacks of gout.

Other classes of medications to treat high blood pressure include beta blockers, angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), calcium channel blockers, adrenergic inhibitors (such as centrally acting alpha agonists and alpha blockers) and vasodilators. In some cases, two classes of medications may be combined in one pill.

Beta blockers: Beta blockers slow the heart rate and lower blood pressure.
Benefits: Beta blockers reduce the amount of oxygen required by the heart and decrease the heart's workload. They can also reduce the risk of developing heart disease.

Risks: Side effects include dizziness. Beta blockers aren't recommended for people who have certain respiratory problems, such as asthma.


ACE inhibitors: Angiotensin is a chemical your body releases during heart failure to hold onto fluid and salt. It also narrows your blood vessels and raises your blood pressure. ACE inhibitors stop the conversion of the chemical angiotensin I into angiotensin II, its active form.
Benefits: ACE inhibitors lower blood pressure, slow the progression of heart failure, and promote long-term improvement in heart function. If you're at high risk for heart failure, ACE inhibitors can help delay its onset.

Risks: Side effects include dizziness, cough, and swelling of the face and lips.


Angiotensin II receptor blockers (ARBs): Angiotensin II receptor blockers work by blocking the effects of angiotensin II.
Benefits: Angiotensin II receptor blockers improve symptoms of heart failure. If you have diabetes and high blood pressure, ARBs may help prevent kidney damage. ARBs may be substituted when ACE inhibitors aren't tolerated.

Risks: The most common side effect of ARBs is dizziness.


Calcium channel blockers: Calcium channel blockers decrease the heart's workload, reduce pressure in the arteries and increase the amount of oxygen delivered to the heart.
Benefits: Calcium channel blockers lower blood pressure and may lower the risk of having a heart attack or stroke, especially if you're at high risk for these conditions.

Risks: The most common side effects are fatigue and leg swelling, but side effects vary depending on the specific medication taken. Some calcium channel blockers aren't recommended for people who have heart failure or have had a heart attack.


Other adrenergic inhibitors: These medications include alpha blockers and centrally acting alpha agonists that lower blood pressure by acting on various parts of the sympathetic nervous system.
Benefits: The benefits depend on the specific medication. Some medications, such as the alpha blockers, may lower blood pressure and blood lipid levels in addition to relieving symptoms of prostate enlargement.

Risks: Side effects include sedation and dry mouth.


Vasodilators: Vasodilators lower blood pressure by dilating, or widening, the blood vessels.
Benefits: Vasodilators are often effective when hypertension is severe or hasn't responded to other types of medications.

Risks: Side effects include headache, increased heart rate and fluid retention. Often, these side effects can be prevented with another medication, such as a beta blocker.

If your doctor prescribes blood pressure medication, follow his or her instructions carefully. You may need to make adjustments in your diet, for example, if you're prescribed a diuretic that causes potassium loss. Make sure your doctor is aware of any other medications you're taking or have recently taken, including prescription and over-the-counter drugs and herbal or nutritional supplements.

Keep in mind that various other medications may interfere with or increase the potential for side effects from blood pressure medication. This includes over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs, such as ibuprofen), nasal decongestants, cold medications, diet pills and herbal remedies. Licorice, for example, contains a substance that may cause sodium retention and potassium loss. It may elevate your blood pressure as well as interact with your blood pressure medication.

Certain prescription medications may also be problematic, including:

steroids, such as prednisone
cyclosporine (used for transplant patients)
erythropoietin
tricyclic antidepressants
monoamine oxidase inhibitors (MAO inhibitors)
birth control pills
nonsteroidal anti-inflammatory drugs (NSAIDs)
If your doctor prescribes blood pressure medication, only stop taking it under your doctor's supervision. Stopping the medication may cause an abrupt elevation in blood pressure.


Complications of high blood pressure
The major complications from high blood pressure primarily involve the heart, arteries (blood vessels that carry oxygen away from the heart), kidney, brain and eyes.
Heart and blood vessel complications: Pumping becomes more difficult. An enlarged and overworked heart can result in various conditions, such as heart failure or heart attack. Hypertension is also believed to speed the formation of cholesterol buildup in the heart's blood vessels and elsewhere in the body, as well as thickening of the heart wall muscle.

Brain complications: The main risks are stroke, bleeding into the brain and rupture of aneurysms, or weaknesses in blood vessel walls.

Kidney complications: Kidney function may deteriorate, leading to the need for dialysis, a procedure used to filter waste products from the bloodstream.

Eye complications: Bleeding can occur in the retina (the light-sensitive tissue found at the back of the eye), which may contribute to altered vision. Uncontrolled, severe high blood pressure may lead to vision loss or blindness.
To help reduce the risk of cardiovascular disease, the U.S. Preventive Services Task Force recommends that adults who have high blood pressure be screened for diabetes.


Pregnancy-specific information
Chronic hypertension increases the risk of poor fetal growth and preeclampsia (a serious condition that usually develops after the 20th week of pregnancy). Proper treatment can significantly lower the rate of serious complications for both mother and baby.
Your doctor will closely monitor your blood pressure throughout your pregnancy. If necessary, blood pressure medications may be prescribed (or changed to those preferred during pregnancy). If left untreated, high blood pressure and preeclampsia can be fatal.


Senior-specific information
Again, the risk of developing high blood pressure increases with age. Older adults may also experience more side effects of medications.
According to the latest findings from the Framingham Heart Study (published by the National Institutes of Health), diastolic blood pressure typically plateaus after age 60. For older adults, systolic blood pressure then becomes a more accurate predictor of future health complications.


Prevention
For most people, high blood pressure prevention requires a comprehensive approach.
Diet
A diet rich in fruits and vegetables and low in dairy products, cholesterol and fat (including saturated and total fats) may significantly lower blood pressure. Increasing dietary fiber may also lower your blood cholesterol levels, which can help decrease the risk of heart disease. Limit your daily sodium intake to no more than 2.4 grams of sodium or 6 grams of sodium chloride (about 1 teaspoon of table salt). Also decrease the amount of processed foods in your diet, as they're often high in sodium. Finally, make sure you get enough potassium, calcium and magnesium.

Weight control and exercise
If you're overweight, lose the extra pounds. Most days of the week, get between 30 and 60 minutes of aerobic activity. Consult your doctor before beginning an exercise program.

Alcohol intake
Limit your daily alcohol intake. No more than 1 ounce of ethanol a day is recommended for men. This is about 24 ounces of beer or 10 ounces of wine. Women and people of lighter weight are recommended to have no more than ½ ounce of ethanol a day.

Smoking
If you smoke, quit. Smoking increases the risk of atherosclerosis (buildup of cholesterol, lipids, plaque and other materials in the arteries) and heart disease.