Hypertension in the pediatric population is now commonly observed. Hypertension is known to be a major cause of morbidity and mortality in the United States and in many other countries, and the long-term health risks to children with hypertension may be substantial. In the United States, extensive normative data on blood pressure (BP) in children are available.
The Task Force on Blood Pressure Control in Children, commissioned by the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health (NIH), developed standards for BP by using the results of 11 surveys of more than 83,000 person-visits of infants and children (including approximately equal numbers of boys and girls). The percentile curves were first published in 1987 and describe age-specific distributions of systolic and diastolic BP in infants and children, with corrections for height and weight. 
The Third Report of the Task Force, published in 1996, provided further details regarding the diagnosis and treatment of hypertension in infants and children.  In 2004, the Fourth Report added normative data and adapted the data to growth charts from the Centers for Disease Control and Prevention (CDC) for 2000.  In accordance with the recommendations of the Task Force, BP is considered normal when the systolic and diastolic values are less than the 90th percentile for the child’s age, sex, and height.
The Fourth Report introduced a new category, prehypertension, which is diagnosed when a child’s average BP is above the 90th percentile but below the 95th. Any adolescent whose BP is greater than 120/80 mm Hg is also given this diagnosis, even if the BP is below the 90th percentile. This classification was created to align the categories for children with the categories for adults from the recommendations of the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure.
Stage I hypertension is diagnosed if a child’s BP is greater than the 95th percentile but less than or equal to the 99th percentile plus 5 mm Hg. Stage II hypertension is diagnosed if a child’s BP is greater than the 99th percentile plus 5 mm Hg. It may be categorized as prehypertension if the BP is between 90th to 95th percentile.
If the systolic and diastolic pressures give rise to a discrepancy with respect to classification, the child’s condition should be categorized by using the higher value. Table 1 (see below) serves as a guide to the practicing physician. Full blood pressure tables for children and adolescents are available from the NHLBI.
|Age, y||95th BP Percentile for Girls, mm Hg||95th BP Percentile for Boys, mm Hg|
|50th Height Percentile||75th Height Percentile||50th Height Percentile||75th Height Percentile|
BP is determined by the balance between cardiac output and vascular resistance. A rise in either of these variables, in the absence of a compensatory decrease in the other, increases mean BP, which is the driving pressure.
Factors that affect cardiac output include the following  :
Effective circulating volume - Atrial natriuretic hormones, mineralocorticoids, angiotensin
Sympathetic nervous syndrome
Factors that affect vascular resistance include the following  :
Pressors - Angiotensin II, calcium (intracellular), catecholamines, sympathetic nervous system, vasopressin
Depressors - Atrial natriuretic hormones, endothelial relaxing factors, kinins, prostaglandin E 2, prostaglandin I 2
Changes in electrolyte homeostasis, particularly changes in sodium, calcium, and potassium concentrations, affect some of these factors.
Under normal conditions, the amount of sodium excreted in the urine matches the amount ingested, resulting in near constancy of extracellular volume. Retention of sodium results in increased extracellular volume, which is associated with an elevation of BP. By means of various physical and hormonal mechanisms, this elevation triggers changes in both the glomerular filtration rate (GFR) and the tubular reabsorption of sodium, resulting in excretion of excess sodium and restoration of sodium balance.
A rise in the intracellular calcium concentration, due to changes in plasma calcium concentration, increases vascular contractility. In addition, calcium stimulates release of renin, synthesis of epinephrine, and sympathetic nervous system activity. Increased potassium intake suppresses production and release of renin and induces natriuresis, decreasing BP.
The complexity of the system explains the difficulties often encountered in identifying the mechanism that accounts for hypertension in a particular patient. These difficulties are the main reason why treatment is often designed to affect regulatory factors rather than the cause of the disease.
In a child who is obese, hyperinsulinemia may elevate BP by increasing sodium reabsorption and sympathetic tone.
Hypertension can be primary (ie, essential) or secondary. In general, the younger the child and the higher the BP, the greater the likelihood that hypertension is secondary to an identifiable cause (see Table 2 below). A secondary cause of hypertension is most likely to be found before puberty; after puberty, hypertension is likely to be essential.
Table 2. Common Causes of Hypertension by Age (Open Table in a new window)
|1-6 y||7-12 y|
Thrombosis of renal artery or vein
Congenital renal anomalies
Coarctation of aorta
Renal artery stenosis
Renal parenchymal disease
Coarctation of aorta
Renal parenchymal disease
Renal parenchymal disease
A review of the literature revealed that most of the young patients with secondary hypertension had a renal parenchymal abnormality; in the remaining patients, the causes of hypertension (in order of frequency) were renal artery stenosis, coarctation of the aorta, pheochromocytoma, and a variety of other conditions. [5, 6]
United States statistics
The true incidence of hypertension in the pediatric population is not known. This vagueness partly stems from the somewhat arbitrary definition of hypertension and is in part related to incomplete blood pressure screening during routine pediatric clinical visits. The prevalence of systemic hypertension in children appears to be increasing and is estimated to be 2% to 5%, especially in view of the growing population of children with obesity.
In adults, hypertension is defined on the basis of data from extensive studies that allowed correlation of BP with adverse events, such as heart failure or stroke. Similar studies have not been performed in children, although reports from small populations of children provided compelling evidence of a relation between hypertension and both ventricular hypertrophy and atherosclerosis.
In children, the definition of hypertension is based exclusively on frequency-distribution curves for BP. As a consequence, estimates of the prevalence of pediatric hypertension lack a scientific basis. The number of children who might be defined as having hypertension and the frequency with which they develop complications during adulthood remain unknown. However, recent evidence indicates that hypertension in adults originates in childhood, because childhood blood pressure predicts blood pressure in the adult. [7, 8]
Because of differences in genetic and environmental factors, incidences vary from country to country and even from region to region in the same country.
Height and weight affect BP. However, these relations do not become evident until children reach school age. The Task Force on Blood Pressure Control in Children considered these factors when they published their normative data in 1987. 
Numerous investigators have noted a correlation between the BP of parents and that of their offspring. Familial aggregation of BP is detectable early in life. Some data relate this association to concomitant obesity in both parent and child.
There are no significant differences in BP between girls and boys younger than 6 years. From that age until puberty, BP is slightly higher in girls than in boys. At puberty and beyond, BP is slightly higher in male adolescents and men than in comparably aged female adolescents and women.
The Task Force on Blood Pressure Control in Children noted no differences in BP between African American and white children. However, both peripheral vascular resistance and sensitivity of BP to salt intake appear to be greater in African American children than in white children, at any age.
High blood pressure is a precursor of heart attacks and strokes, as has been well established in the adult literature.
Obese children have approximately a 3-fold higher risk for hypertension than nonobese children.  As many as 41% of children with high BP have left ventricular hypertrophy (LVH).  Almost 60% of children with persistent elevated BP have relative weights greater than 120% of the median for their sex, height, and age. As in adults, in whom abdominal girth correlates to elevated blood pressure, studies show that this measurement is also to be considered in the assessment of a teenager with suspected BP elevation at an early age. 
Parents, caregivers, and children themselves must be properly advised about restriction of exercise, when appropriate. They must also be informed about the potential adverse effects of medication. Finally, it is vital to educate parents, caregivers, and children about the potential complications of persistent hypertension.
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