General Discussion

The relevance of childhood blood pressure (BP) measurement to pediatric health care and the development of adult essential hypertension has undergone substantial conceptual change during the past two decades. Hypertension and its sequelae traditionally have been considered a disease acquired in middle age, but hypertension often begins in childhood and adolescence. It is now understood that hypertension detected in some children may be a sign of an underlying disease, such as renal parenchymal disease, whereas in other cases the elevated BP may represent the early onset of essential hypertension. The awareness of pediatric hypertension among the medical community and general public has increased in recent years, leading to increasing numbers of hypertensive children coming to medical attention. Hypertension present in childhood predisposes the patient to cerebrovascular disease, left ventricular hypertrophy, atherosclerosis, coronary artery disease, and retinal changes.

The most commonly used definitions of normal and abnormal BP in childhood come from the National High Blood Pressure Education Program Working Group. These definitions are endorsed in the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7). Normal BP is defined as systolic and diastolic BP less than the 90th percentile for age and sex. High-normal BP is defined as average systolic or diastolic BP greater than or equal to the 90th percentile but less than the 95th percentile. Hypertension is defined as average systolic or diastolic readings greater than the 95th percentile based on age, gender, and height percentile (Tables 27-1 and 27-2). At least three abnormal readings, obtained on separate occasions over a period of several weeks, should be obtained before entertaining a diagnosis of hypertension in an individual patient. A separate set of BP percentile curves has been established for infants aged 0 to 12 months (Figures 27-1 and 27-2).

Table 27-1 90th and 95th Percentile Blood Pressures for Boys Aged 1 to 17 Years by Height Percentile

Table 27-2 90th and 95th Percentile Blood Pressures for Girls Aged 1 to 17 Years by Height Percentile.

Figure 27-1 Age-specific percentiles of blood pressure measurements in boys—birth to 12 months of age.

(From Task Force on Blood Pressure Control in Children. Report of the second task force on blood pressure control in children—1987. Pediatrics 1987;79:1–25, with permission.)

Figure 27-2 Age-specific percentiles of blood pressure measurements in girls—birth to 12 months of age.

(From Task Force on Blood Pressure Control in Children. Report of the second task force on blood pressure control in children—1987. Pediatrics 1987;79:1–25, with permission.)

The causes of hypertension in children are diverse, with a significantly greater percentage of hypertensive children having secondary forms of hypertension compared with adults. In children, most causes of secondary hypertension are renal in origin. Essential (primary) hypertension becomes more prevalent with increasing age to the point that most older adolescents with hypertension have the primary form.

BP in childhood may predict adult BP. The Muscatine study demonstrated subjects with diastolic BP, above the 90th percentile in childhood to be twice as likely to develop adult hypertension than expected. In addition, the likelihood of developing adult hypertension increased with increasing numbers of childhood readings above the 90th percentile. The absence of abnormal readings in childhood was associated with a reduced risk of developing adult hypertension. Although a single elevated blood pressure measurement in childhood does not necessarily predict the future development of hypertension, such a child should be monitored more closely. In addition, the child should be monitored for the presence of other cardiovascular risk factors, such as hyperlipidemia.

Current recommendations are for all children 3 and older to have blood pressure measured with every visit to their health care provider. Children under 3 with risk factors such as low birth weight, extended stay in the neonatal intensive care unit (NICU), cardiac abnormalities, recurrent urinary tract infections (UTIs), known or family history of renal disease, or solid organ transplants should have BP measurements with each clinical visit.

A conventional mercury column or aneroid sphygmomanometer is recommended, although an automated oscillometric device may be used in infants and toddlers who will not cooperate with manual BP measurement. The bladder of the cuff should encircle 80% to 100% of the circumference of the upper arm, and its width should be at least 40% of the upper arm circumference. The disappearance of the 5th Karotkoff sound is used to define the diastolic BP.