EVALUATION AND MANAGEMENT OF HYPERTENSION IN CHILDREN AND ADOLESCENTS
Incidence: < 5%, possibly as low as 1.1%.
Definition: Based on statistics for children > one year old. Hypertension is defined as systolic and/or diastolic blood pressure (BP) > 95th percentile for gender, age, and height (see tables in Pediatrics 1996;98:649-58).
Absent severe hypertension or end-organ damage, elevated BP should be documented three times during each of at least three clinic visits spaced months apart. (Normotension is defined as systolic and diastolic BP < 90th percentile for gender, age, and height.)
Classification: Primary vs. secondary, a useful distinction. Secondary hypertension is more common in prepubertal children < 12 years old, likely to be more pronounced, and associated with treatable and potentially correctable disorders, usually renal disease or coarctation. Primary (“essential”) hypertension is more common in adolescents and often associated with obesity.
Identification: AAP recommends that routine BP measurements commence at age three.
Technique is important. Cuff bladder width should equal 40% of the circumference of the upper arm at its midpoint; bladder length should equal 80-100% of the circumference of the upper arm at its midpoint. An array of cuffs should be available including large adult and thigh cuffs. After the patient has been sitting quietly for five minutes, BP should be measured with the patient still seated and with the arm supported at heart level. First use palpatory, then auscultatory technique. Diastolic pressure is defined as disappearance of Korotkoff sounds except when > 10 mm Hg separate muffling and disappearance. Then, muffling represents diastolic pressure. (Note that the aforementioned tables use disappearance of Korotkoff sounds for diastolic pressure.) Measure leg pressures similarly but with the patient prone. Avoid “white-coat hypertension.” Liberally use ambulatory BP monitoring to avoid false positive diagnoses. Measurements should be made at normal room temperature more than 60 minutes after meals, ingestion of caffeine, strenuous exercise, or smoking.
History: Focus review of systems on renal, cardiovascular, and endocrine systems. Ask about enuresis, hematuria, edema, back or abdominal pain, fatigue, chest pain, dyspnea on exertion, palpitations, heat sensitivity, diaphoresis, weight loss, pallor, headache, seizures, focal neurological symptoms, blurred vision. Inquire about chronic illness, hospitalization, trauma, pregnancy. Seek family history of hypertension, renal disease, cardiovascular disease, diabetes. Ask about prescription or over-the-counter medications (oral contraceptives, steroids, caffeine, ephedrine) and substance abuse (ethanol, tobacco, amphetamines, Ecstasy, cocaine, anabolic steroids).
Physical Examination: Measure growth parameters and calculate body mass index (BMI = weight in kg ÷ square of height in meters; > 25 implies overweight, > 30 implies obese). Seek telltale findings: diminished or absent lower extremity pulses (coarctation); virilization, hypogonadism, pseudohermaphroditism (congenital adrenal hyperplasia); moon facies, buffalo hump, striae (Cushing syndrome); café-au-lait spots (pheochromocytoma or neurofibromatosis with renal artery stenosis); warm and moist skin, tachycardia, hyperactive reflexes, thyromegaly (hyperthyroidism); elfin facies, mental retardation (William syndrome). Perform or obtain a funduscopic examination. Listen for cardiac murmurs, abdominal bruits. Palpate the precordium and abdomen.
Laboratory Evaluation: Recommended screening for hypertensive patients commonly includes urinalysis and culture, basic metabolic panel, lipid panel, CBC with platelets, and renal ultrasonography with renal artery Doppler evaluation. Severity of hypertension can be assessed by looking for end-organ damage, e.g., left ventricular hypertrophy (LVH), hypertensive retinopathy, microalbuminuria, carotid thickening. The most common end-organ damage is LVH (LV mass > 95th percentile), which is present in 40-50% of children with primary hypertension and is severe (LV mass >99th percentile) in 14%. Echocardiography is a sensitive and readily available detector of LVH.
Treatment: Except for severely hypertensive patients (usually with secondary hypertension), benefits of therapy for hypertensive children and adolescents will often become apparent only in adulthood (decreased risk of stroke, coronary artery disease, heart failure, and renal failure).
Absent symptoms or end-organ damage, there simply are no immediate clinical end points that demand treatment of mildly to moderately hypertensive children and adolescents. The rationale for treating these patients is that tracking studies show them to be at increased risk of becoming hypertensive adults.
Secondary hypertension is remedied by identifying and treating the underlying etiologic disorder and by lowering BP pharmacologically as necessary.
Treatment of primary hypertension is multifaceted. Lifestyle modification (tobacco cessation, weight loss, salt restriction, and aerobic exercise) should be instituted before considering drug therapy.
Lifestyle modification is difficult to implement, and compliance is usually poor, because such intervention impacts patients’ habits and social milieu and because it is time-consuming and often expensive. Nonetheless, referrals to nutritionists, weight-loss programs, and exercise programs can be productive.
Hypertensive children should cease tobacco use to decrease cardiovascular and other risk.
Weight is probably the major determinant of BP in children and adolescents. A relationship between obesity and BP has been demonstrated as early as age five. 35-50% of hypertensive adolescents are obese. A randomized trial assigned obese adolescents regimens of diet plus exercise, diet alone, and no intervention. Changes in systolic BP at 20 weeks were
-16, -10, and + 4 mm Hg, respectively. Weight control programs most likely to be successful over time may prove to be those directed toward younger children, even infants. The increasing prevalence of obesity in children can be expected to lead to an increased incidence of hypertension in children and adolescents.
Although sodium restriction has not been proven to benefit all children and adolescents with primary hypertension, some do respond. In a trial randomly assigning newborns to normal- and low-sodium diets for a period of six months, lower BP was found after the six-month period and again 15 years later in subjects fed a low-sodium diet. Other studies have shown no benefit from salt restriction for primary hypertension in children and adolescents. The Task Force Report on High Blood Pressure in Children and Adolescents and the American Heart Association do recommend moderate restriction of sodium. This can be accomplished using a no-added-salt diet with reduction or elimination of salt-rich foods including some foods in school lunch programs. Compliance with sodium restriction can be determined from 24-hour urine collections or, more conveniently, from random measurement of sodium and creatinine concentrations in first morning specimens.
Exercise appears to lower BP in children and adolescents. Among hypertensive children randomly assigned to added school PE sessions or no added exercise for eight months, added exercise was associated with reduction in BP. As mentioned above, exercise combined with diet in adolescents had a greater antihypertensive effect than diet alone. The American College of Sports Medicine recommends 20-60 minutes of aerobic exercise 3-4 times weekly. Exercise intensity should be sufficient to cause heart rate to reach 60-85% of age-related maximum heart rate. Data concerning safety of participation in athletics by children with mild hypertension are unavailable. It is generally believed that participation is allowable absent symptoms or end-organ damage. However, isometric exercise, which does not appear to lower BP, should be discouraged until BP is controlled. Weight lifting can acutely raise BP as high as 230-330/170-250 mm Hg.
Oral contraceptives may be contraindicated in sexually active hypertensive girls.
Drug therapy is often indicated for secondary hypertension, moderate or symptomatic hypertension, patients who fail lifestyle modification, and patients with end-organ damage. Drug therapy should be designed to maximize compliance and minimize adverse effects, and it should supplement, not replace, lifestyle modification.
For secondary hypertension, drug therapy should be directed against underlying pathphysiology, e.g., a diuretic or vasodilator for acute glomerulonephritis, an ACE inhibitor or angiotensin-receptor antagonist for diabetes.
There have been no large randomized or comparative trials concerning optimal intial drug therapy for children and adolescents with primary hypertension. Calcium-channel blockers (nifedipine, amlodipine) and ACE inhibitors (captopril, enalapril, lisinopril) have been shown to be safe and effective in children and are commonly prescribed. Calcium-channel blockers are contraindicated in patients with sick sinus syndrome but may be preferable in patients with asthma. ACE inhibitors (and angiotensin-receptor antagonists) are contraindicated in pregnancy and should be used with caution in sexually active girls and patients with bilateral renovascular hypertension or volume depletion. Beta blockers (propranolol, atenolol, metoprolol, labetalol) were among the first and most widely used antihypertensive drugs for children. They are contraindicated in patients with asthma or heart block and should be used with caution in patients with diabetes. They may cause lethargy, weakness, and fatigue.
The recent ALLHAT study showing low-dose thiazide superior to other agents for initial treatment of adult hypertension has uncertain implications for children and adolescents. Thiazide diuretics are safe and effective in children, but metabolic complications (hypokalemia, glucose intolerance, adverse lipid effects) associated with previously recommended high doses have limited their use. Although there are no data on low-dose thiazide therapy in hypertensive adolescents, an alternative to a calcium-channel blocker or ACE inhibitor may be hydrochlorothiazide 12.5 mg/d (0.2 mg/kg/d). If combination therapy is required, an ACE inhibitor can be added. Low-dose thiazide therapy, alone or in combination, will be enhanced by salt restriction.
Treatment Goals: Reduction of systolic and diastolic pressure to < 90-95th percentile for gender, age, and height depending on the etiology and severity of the hypertension. Greater reduction should be sought in children with diabetes.
Follow-up: Includes ongoing monitoring of BP (preferably at home, clinic and ambulatory BP monitoring as needed), continued emphasis on lifestyle modification, and, on an as-needed basis, follow up laboratory testing for medication side effects, follow up lipid panels, follow up funduscopic examinations, and follow up echocardiograms. Gradual discontinuation of drug therapy can be attempted in patients with initially mild hypertension who are well-controlled on a single drug and who are compliant with lifestyle modification.
The assistance of Raymond D. Adelman, M.D., pediatric nephrologist, is gratefully acknowledged.