Hypertension

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Chapter 27 HYPERTENSION

Kevin Haggerty

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.

Key Physical Findings

Height and weight percentiles

Vital signs with systolic and diastolic BPs matched against standards for age, sex, height (see Tables 27-1 through 27-2). Consider measuring the BP in all four extremities regardless of the child’s age to evaluate for coarctation of the aorta.

Funduscopic examination to evaluate for microvascular changes, pinpoint hemorrhages, and “cotton wool” spots pinpoint.

Head and neck examination to evaluate for moon facies, suggestive of Cushing syndrome; a webbed-neck, suggestive of Turner syndrome; or tonsillar hypertrophy, which may result in obstructive sleep apnea. The thyroid should be palpated for thyromegaly.

Cardiovascular examination for tachycardia, murmur, friction rub, or apical heave

Pulmonary examination

Abdominal examination for a palpable mass or abdominal bruit

Genital examination for ambiguous genitalia

Skin examination for flushing or diaphoresis suggestive of pheochromocytoma, café au lait spots suggestive of neurofibromatosis, malar rash suggestive of lupus, or acanthosis nigracans suggestive of diabetes

Initial Work-Up

Many hypertensive children will have otherwise normal physical examinations, even in the presence of significant underlying renal or other organ system disease. Therefore, laboratory testing is usually necessary to complete the child’s evaluation. The child’s age, history, physical examination findings, and degree of BP elevation should be used to decide what are the most appropriate studies for a particular child. All hypertensive children should undergo the following screening laboratory tests:

Additional Work-Up

Specific laboratory tests (as indicated by the history, physical examination, and screening tests):

24-hour urine collection for protein excretion and creatinine clearance	If renal disease is suspected or determined by the screening tests
Urine and serum catecholamines	If pheochromocytoma is suspected
Serum cortisol level	If Cushing’s syndrome is suspected
Thyroid-stimulating hormone (TSH), thyroxine (T₄), tri-iodothyronine (T₃)	If a thyroid disorder is suspected
Echocardiogram	If cardiac disease is suspected on the basis of a murmur or other abnormal finding on physical examination. An echocardiogram for all hypertensive children is suggested by some authorities because left ventricular hypertrophy can be present even in children with mild hypertension.
Serum 17α-hydroxyprogesterone	If congenital adrenal hyperplasia is suspected
Plasma aldosterone	If hyperaldosteronism is suspected
Renal ultrasound	If renal disease is suspected to evaluate the contour and texture of the kidneys and to screen for gross renal abnormalities
Computed tomography (CT) scan of abdomen and pelvis	If an abdominal mass is palpated on physical examination to evaluate for the presence of tumor

Specialized studies (typically performed at referral centers or by pediatric subspecialists in the evaluation of pediatric hypertension):

Plasma rennin and 24-hour urinary sodium excretion	To evaluate for renal artery stenosis
Renal ultrasound with Doppler study of renal arteries	To evaluate for renal artery stenosis
Captopril challenge test	To evaluate for renal artery stenosis
Renal angiography with renal vein renins	To evaluate for renal artery stenosis
Magnetic resonance angiography	To evaluate for renal artery stenosis
Captopril renal scan	To evaluate for renal artery stenosis
Ambulatory BP monitoring	Not yet endorsed by consensus bodies for routine use in children, but may affect the management of childhood hypertension and may predict the presence of secondary hypertension
Renal biopsy	To establish a tissue diagnosis in renal disease
Angiography	To evaluate for renal artery stenosis