Blood pressure, measured with a blood pressure cuff and stethoscope by a nurse or other health care provider, is the force of the blood pushing against the artery walls.
Two numbers are recorded when measuring blood pressure:
The higher number, or systolic pressure, refers to the highest pressure inside the artery. It occurs when the heart contracts and pumps blood into the body.
The lower number, or diastolic pressure, refers to the lowest pressure inside the artery. It occurs when the heart relaxes and fills with blood.
Each time the heart beats, it pumps blood into the arteries, resulting in the highest blood pressure, the systolic pressure, as the heart contracts, and the lowest blood pressure, the diastolic pressure, as the heart relaxes.
Both the systolic and diastolic pressures are recorded as "mm Hg" (millimeters of mercury). This recording represents how high the mercury column is raised by the pressure of the blood.
High blood pressure means that there is higher than normal pressure inside the arteries either during systole (when the heart contracts and pumps blood through the body), or during diastole (when the heart relaxes and fills with blood).
If the pressure is high during the pumping phase (systole), then the first number recorded with a blood pressure reading (the systolic pressure) will be high.
If the pressure is high during the relaxation phase (diastole), then the second number recorded (the diastolic pressure) will be high.
High blood pressure is also called hypertension.
Blood pressure can be affected by many factors, including the following:
The time of day. Blood pressures fluctuate during waking hours, and are lower as we sleep.
Physical activity. Blood pressure is usually higher during and immediately after exercise, and lower at rest.
Emotional moods. Feelings (such as fear, anger, or happiness) can affect blood pressure.
Stress. Physical or emotional stress can elevate blood pressure.
Your child's age, height, weight, and gender. Blood pressure varies for each child.
Other illnesses. Other illnesses your child may have (such as kidney or heart disease) affects blood pressure.
Children (and adults) may be anxious in a doctor's office, not knowing what may happen and being afraid of a possibly painful experience ahead of them. Infants, toddlers, and preschoolers may be fearful of being separated from their parent or caregiver. Many emotions related to visiting the clinic can affect blood pressure and may give falsely high readings.
Before determining that your child has high blood pressure, a doctor or nurse will take several readings when your child is calm and you are present to comfort him or her, if needed. The staff may let some time lapse before retaking a blood pressure reading, to make sure your child has rested and has become calm. More meaningful blood pressure readings can be obtained this way.
Blood pressures vary depending on the age of your child, as well as according to height and weight, and the gender of your child. Generally, blood pressure is low in infancy, and rises slowly as children age. Boys' blood pressures are slightly higher than girls' are, and taller people generally have higher blood pressures than short people do.
For example, an infant may have a quite normal blood pressure of 80/45 mm Hg, while that value in an adult is considered low. A teenager may have an acceptable blood pressure of 110/70 mm Hg, but that value would be of concern in a toddler.
The National Heart, Lung, and Blood Institute has prepared a series of age- and gender-specific blood pressure measurement tables for children ages 3 through 17 years, based on percentiles. A range of blood pressure values is given based on how old and how tall your child is. According to the tables, if your child has a blood pressure that is higher than 90 to 95 percent of other boys or girls his or her age and height, then he or she may have high blood pressure.
Again, many factors, including emotions, can affect blood pressure. Readings that are high compared to the values on the table may need to be investigated further by your child's doctor.
The prevalence of hypertension and obesity in children age 8 to 17 has increased in all racial and ethnic groups since 2002.
High blood pressure, or hypertension, directly increases the risk of coronary heart disease (heart attack) and stroke (brain attack). With high blood pressure, the arteries may have an increased resistance against the flow of blood, causing the heart to pump harder to circulate the blood.
Heart attack and stroke related to high blood pressure are rare in children and adolescents. Yet, studies of young adults with high blood pressure found that many had high blood pressure as a child. By their 20s, studies show that children and adolescents with high blood pressure will exhibit harmful effects on the heart and blood vessels even with mild hypertension.
Blood pressure is classified as "primary," or without a definite cause, and "secondary," or related to an illness or behavior.
Factors that seem to contribute to primary hypertension in adults, and possibly in children, include the following:
High blood cholesterol levels
Secondary causes of hypertension in children include the following:
Illnesses. The kidneys play an important role in regulating blood pressure, and often have diminished ability to perform this vital task when they are diseased. A congenital (present at birth) heart defect called coarctation of the aorta may also cause high blood pressure readings. Head injury may raise the pressure inside the brain, which affects the body's ability to regulate blood pressure normally.
Use of prescription or illegal recreational drugs (such as steroids taken to decrease inflammation, oral contraceptives, or cocaine)
Immobility (such as with a chronic illness)
Severe pain (such as with cancer or burns)
Primary hypertension (with an unknown cause) is the most common cause of high blood pressure in adolescents and adults, but is less common in children.
Many children with high blood pressure also have adult relatives with hypertension, so there may be a hereditary aspect to the disease.
There is a higher incidence of high blood pressure in African-American children after the age of 12 and into adulthood.
Your child's doctor may note an elevated blood pressure reading during a routine office visit. Obtaining calm, resting blood pressures on several different occasions (days, weeks, or months apart) will provide better information about whether the blood pressure elevation is consistent or due to fear or stress.
Your child's doctor will obtain a medical history, including information about your child's diet, exercise level, home and school activities, and possible stressors. A physical examination may also be performed.
Diagnostic tests may help determine if your child's high blood pressure is related to an illness, or is "essential" or "primary" hypertension, meaning it has no known cause. Diagnostic procedures may include:
Blood tests (including those to evaluate kidney function and cholesterol levels)
Other tests may be needed to evaluate the health of other organs (such as the heart or kidneys) which may contribute to hypertension.
Specific treatment for high blood pressure will be determined by your child's doctor based on:
Your child's age, overall health, and medical history
Extent of the condition
Your child's tolerance to specific medications, procedures, or treatments
Expectations for the course of the condition
Your opinion or preference
If a secondary cause has been found, such as kidney disease, the underlying disease will be treated. If no cause has been determined, the first treatment approach is lifestyle therapy, including the following:
Increasing physical activity
These interventions can lower systolic and diastolic blood pressure, improve the strength of the heart, and lower blood cholesterol. These are all important steps in preventing heart disease as an adult.
Medications to control high blood pressure are only needed in about 1 percent of children with the disorder. Consult your child's doctor for more information.