Blood pressure is the force exerted by the blood as it courses through the circulatory system. If this force is consistently too high, it can damage blood vessels in the brain, eye, heart and kidneys and lead to a number of complications, including strokes and heart failure.
Most people think of high blood pressure as a disease of adulthood. It is true that primary or essential hypertension—the type that has no clear cause and produces no symptoms until it is advanced—is detected mainly in the adult years. Increasing evidence, however, shows that essential hypertension often develops in adolescence. Young children, too, can have essential hypertension, although it is more unusual.
Severe blood pressure elevations in infants and small children usually result from secondary hypertension, which in turn is caused by an underlying disorder such as heart or kidney disease.
HOW DOES HIGH BLOOD PRESSURE DEVELOP?
Normal blood pressure rises and falls depending on activity, time of day and several other factors. These variations occur within a normal range because of a complex system of chemical signals that regulate the pressure of the heart's contractions, the amount of blood in the circulation and the amount of resistance or tension in blood vessels. High blood pressure can develop when an organ malformation or disease process such as kidney inflammation disrupts this system. Presumably, some similar disruption occurs in essential hypertension, but the exact nature of the problem is unknown.
WHEN SHOULD I SUSPECT THAT MY CHILD HAS HIGH BLOOD PRESSURE?
In some cases of secondary hypertension, the underlying problem will produce noticeable signs and symptoms. These may include fatigue and difficulty breathing in the case of heart problems and swelling of the hands, feet and face, along with decreased urination, in the case of kidney problems.
Most of the time, though, high blood pressure causes no symptoms, which is why regular blood-pressure checks are so important. Starting at age three, children should have their blood pressure measured at every well-child checkup.
HOW CAN THE PEDIATRICIAN TELL IF MY CHILD HAS HIGH BLOOD PRESSURE?
Doctors measure blood pressure with an inflatable cuff and meter called a sphygmomanometer. The cuff (which should be a special small size for a child) momentarily constricts a large artery while the doctor checks the meter and listens to the sounds of blood flow with a stethoscope. The reading gives two measurements: systolic pressure, which is the pressure when the heart contracts and pushes out blood, and diastolic pressure, which is the pressure while the heart is resting. the reading is given as the systolic over the diastolic pressure—for example, 110 over 70.
High blood pressure is diagnosed on the basis of three separate readings taken at different times. If the average of these three readings is higher than that for 90 percent of children the same age, the child is considered to have hypertension.
Children's blood pressure increases steadily as they grow. In general, a three-year-old with a blood pressure in the vicinity of 98 over 64 (the 75th percentile) is considered in the normal range. Children who are large and heavy for their ages also have higher blood pressure than small children, a factor the doctor will take into account in making the diagnosis.
WHAT TREATMENTS ARE AVAILABLE?
The doctor starts by doing blood and urine tests, as well as X rays of the kidneys, to look for an underlying problem that may be responsible for the blood pressure elevation. If such a problem is found, treating it should control the blood pressure.
Treatment for mild essential blood pressure may involve increasing exercise and reducing salt in the diet. If these measures do not work, or if the blood pressure is quite elevated, the doctor may prescribe medication—most often, a diuretic, which increases excretion of urine.
PREVENTING HIGH BLOOD PRESSURE
• If your child is becoming overweight, consult a registered dietitian for tips on slowing weight gain. Obesity is a major contributor to high blood pressure in children and adults.
• Encourage your child to be physically active.
• If high blood pressure runs in your family, ask your pediatrician to suggest other preventive measures to protect your child. You might, for instance, try limiting the child's consumption of salt.
