Cover article

Recognizing and managing the hypertensive child

By Joseph T. Flynn, MD, MS

Proper measurement of blood pressure is essential both to detect children with hypertension and to avoid over-diagnosis. Once the condition is identified, the pediatrician must decide whether the patient requires lifestyle changes alone or antihypertensive drug treatment as well.

Although hypertension is relatively uncommon in children, awareness of childhood hypertension among both the medical community and the general public has grown in recent years. As a result, greater numbers of children with elevated blood pressure (BP) have come to medical attention. The major stimulus for increased recognition of hypertensive children among pediatricians and pediatric specialists was publication of the first and second reports of the National High Blood Pressure Education Program (NHBPEP) Task Force on Blood Pressure Control in Childhood,^1,2 as well as the more recent Working Group report (also sponsored by the NHBPEP, which is part of the National Institutes of Health).³ These reports, the key points of which are summarized in this article, offer clear guidelines for diagnosis and management of hypertension in childhood, including recommendations for proper methods of BP measurement and warnings against over-diagnosis of hypertension. Such information, by enabling pediatricians to identify and treat childhood hypertension, has the potential to prevent future morbidity, as elevated blood pressure is likely to be the first sign of more significant cardiovascular disease yet to come.

Childhood hypertension defined

Diagnosing hypertension in a child begins with identifying the child's blood pressure as normal or elevated. Because a child's BP increases with age and varies with gender, these two variables must be considered. Therefore, the NHBPEP Task Forces compiled BP readings from tens of thousands of normal children and defined percentiles of BP. Normal BP was set as systolic and diastolic BP below the 90th percentile for age, and hypertension was defined as systolic or diastolic BP (or both) greater than the 95th percentile for age. The NHBPEP Working Group report refined the definition of normal and abnormal BP by incorporating height as an additional variable to be considered in determining whether a child has elevated BP (Tables 1 and 2). It should be noted that the definition of hypertension in children is a statistical one, as opposed to the definition of hypertension in adults, which is based upon clinical endpoints (more on this later).

PLEASE NOTE: If you are using Internet Explorer version 6 or higher, after clicking to enlarge the graphic, click the picture icon that appears in the lower right-hand corner of the graphic.

PLEASE NOTE: If you are using Internet Explorer version 6 or higher, after clicking to enlarge the graphic, click the picture icon that appears in the lower right-hand corner of the graphic.

As illustrated in the box "How to determine if a blood pressure reading is normal," it is now necessary to know the child's height percentile before determining if her BP is normal. This helps prevent over-diagnosis of hypertension by recognizing that "one blood pressure does NOT fit all," because children of the same age can vary widely in height. To further avoid over-diagnosis of hypertension, and because the incidence of hypertension in childhood is undoubtedly well below 5%, it is recommended that at least three abnormal readings, obtained on separate occasions, be obtained before making a diagnosis of hypertension in a child.

The Working Group BP standards apply only to children over 1 year of age. Although similar general definitions of normal BP and hypertension are applied to infants, other issues must be considered, especially in newborns. For this reason, hypertension in infancy will be covered in a separate article in a future issue of Contemporary Pediatrics.

Causes of high blood pressure in the pediatric population

Overall, most childhood hypertension is secondary to an underlying disorder, which, in most cases, is renal disease (see Table 3 in the print edition; Adapted from Flynn JT: Evaluation and management of hypertension in childhood. Prog Pediatr Cardiol 2001;12:177). Primary hypertension does, however, become more common with increasing age; most adolescents with elevated BP do, in fact, have primary hypertension. (The term "essential hypertension" is a misnomer, implying that the high BP is somehow "essential" to the patient's life. Because this is clearly not the case, this term should no longer be used.) Obesity also begins to play a greater role in older children—although whether obese children should be classified as having primary or secondary hypertension is a matter of debate among experts in childhood hypertension. As long as the obese child's evaluation reveals no evidence of another underlying condition, it is probably acceptable to give him a diagnosis of primary hypertension.

Hypertension in children can also have a genetic basis. Although many genetic mutations have been identified in hypertensive individuals, the role of those mutations in the pathophysiology of hypertension remains to be determined. However, it is likely that, as our understanding of the human genome progresses, the "primary hypertension" label now affixed to many hypertensive children will eventually be determined to reflect a genetic mutation.

Obtaining an accurate reading

It is extremely important that the child's BP is measured correctly. Although the BP percentiles of the Task Force and Working Group are based on pressures obtained using mercury column sphygmomanometers, these devices are becoming less common in medical offices because of concerns about the potential hazards of mercury. For this reason, aneroid sphygmomanometers or automated, oscillometric devices such as the Dynamap (Critikon Inc., Tampa, Fla.) will probably be used in most offices. Because a cuff that is too small can result in a falsely elevated BP reading, a variety of cuff sizes should be accessible in your office. The bladder of the cuff should encircle 80% to 100% of the circumference of the upper arm, and its width should be 40% of the upper arm circumference (Figure).³ Given the increasing prevalence of childhood obesity, large adult and thigh cuffs need to be kept on hand as well.

The child should be seated quietly for at least five minutes before BP determination. The arm should be supported at heart level. The Working Group report recommends using disappearance of the Korotkoff sounds (K5) in children of all ages for the diastolic reading³; this represents a change from the first and second Task Force reports.

As emphasized in the Task Force and Working Group reports, the child found to have an elevated BP should have repeat readings obtained before the diagnosis of hypertension is made and a work-up initiated. Generally, this should be done over a period of two or three weeks. It may be helpful to have the child's BP measured outside of the office setting (by, for example, a school nurse or another reliable practitioner) to avoid the "white coat" effect.

Conducting a comprehensive evaluation

Once a child is found to have a persistently elevated BP, the first step in the evaluation is a thorough history and physical examination. The history and review of systems should identify not only symptoms that suggest hypertension but also whether symptoms of an underlying disorder are present. Such symptoms include those of renal disease (enuresis, gross hematuria, edema, fatigue), heart disease (chest pain, exertional dyspnea, palpitations), and diseases of other organ systems (endocrinologic, rheumatologic).

The medical history should include questions about recent as well as chronic illness, hospitalization or episodes of trauma, and recurrent urinary tract infection. The family history should encompass not only hypertension but also diabetes, renal disease, and other cardiovascular disease (hyperlipidemia, stroke). Last, it is important to ask about over-the-counter, prescription, and illicit drug use, because many agents can elevate BP (Table 4).

TABLE 4
Medications and other substances that can elevate blood pressure

The physical examination should begin with determining the child's height and weight percentiles. Poor growth may indicate an underlying chronic illness. Obesity is a significant cause of hypertension, so BMI should be calculated from the height and weight and the BMI percentile determined. At least one lower extremity BP should be obtained, no matter what the child's age, to help rule out coarctation of the aorta (BP is normally 10 to 20 mm Hg higher in the legs than in the arms). The remainder of the physical examination should follow up on clues obtained from the history and focus on discovering specific findings that may provide clues to the cause and severity of hypertension. Examples of important physical exam findings in hypertensive children have been published elsewhere.⁴

Because many hypertensive children have an otherwise normal physical examination, some degree of laboratory testing is usually needed to complete the child's evaluation. Before embarking on laboratory testing, use the child's age, history, physical exam findings, and degree of BP elevation to decide which studies are most appropriate for that particular child. All hypertensive children should undergo the screening laboratory tests listed in Table 5. These can be easily obtained in most primary care offices and community hospitals, and will usually detect whether significant renal disease or another chronic illness is present.

TABLE 5
Laboratory evaluation of the hypertensive child

Of the more specific and specialized tests, only those indicated by the history, physical examination, and screening tests should be obtained. For example, thyroid hormone levels need be obtained only in hypertensive children with symptoms of thyroid disease. If the necessary studies aren't available through your office or local hospital, the child should be sent to a more specialized pediatric center. Reliance on local adult specialists such as cardiologists or nephrologists should be avoided, as they are likely to be unfamiliar with pediatric conditions and normal values for diagnostic studies in children.

Last, the diagnostic evaluation of a hypertensive child would be incomplete without including one or more studies to assess for the presence of hypertensive target-organ damage. Left ventricular hypertrophy (LVH), hypertensive retinopathy, microalbuminuria, and increased thickness of the carotid arteries have all been described in children with primary hypertension.^5–8 If such abnormalities are present, the child should receive antihypertensive drug treatment.

Echocardiography, which is much more sensitive for detecting LVH than electrocardiography,⁶ is probably the most readily available method of target-organ assessment in most areas and should, therefore, be obtained in all hypertensive children. Ambulatory BP monitoring (ABPM), which is increasingly being used in children, can also be helpful in establishing the degree of BP elevation and in ruling out white coat hypertension.⁹ During an ABPM study, the child wears a lightweight oscillometric BP monitor that measures her BP every 20 to 30 minutes during the day and night, giving a profile of the child's BP over a 24-hour period. These studies, in conjunction with data gathered from the history and physical examination, should enable you to determine the severity of the child's hypertension, which is essential for planning treatment and follow-up.

Management is multifaceted

As with hypertensive adults, hypertensive children require a comprehensive approach incorporating patient and family education, nonpharmacologic measures, and antihypertensive medications, as well as monitoring for medication side effects and treatment response. This can be a time-consuming undertaking but it is essential to include all components, because hypertension may be the first sign of more significant cardiovascular disease that may be in the child's future. As with other chronic childhood conditions, prompt recognition and careful management of hypertension may prevent adult disease.

Nonpharmacologic measures. Generally, management should begin with such steps as smoking cessation, weight loss, aerobic exercise, and dietary modifications. Large-scale trials of nonpharmacologic approaches in adults have consistently proved that such "lifestyle measures" reduce BP. Although large-scale trials of nonpharmacologic measures have not been conducted in children, it is reasonable to recommend them, as most of these measures will result in a healthier lifestyle for the child and the rest of the family.

With obesity affecting so many hypertensive children, weight loss is the first nonpharmacologic measure to recommend. In the research setting, reduction of both systolic and diastolic BP has been demonstrated in obese children who lose weight.¹⁰ Unfortunately, as many pediatricians know, these results are hard to duplicate in the primary care setting for many reasons, including family history of obesity, busy family lifestyles, and the growing preference for sedentary entertainment activities such as video games and the Internet. It may be appropriate to refer such children to comprehensive weight loss programs that include not only nutritional intervention but also exercise and family counseling.¹¹

Exercise is frequently recommended as a treatment for hypertension and clearly has a role in the management of hypertensive children. Reviews of the effects of exercise on BP have demonstrated a blood pressure-lowering effect of sustained exercise in both normotensive and hypertensive persons.¹² It is important to emphasize that an aerobic exercise such as running, walking, or cycling is preferred in the management of hypertension, because static exercise activities (such as weight lifting) can lead to dangerous acute BP elevation. It is usually possible to find some form of aerobic exercise that the child enjoys and incorporate it into the treatment plan. Often, the child is already participating in an appropriate activity on occasion and will only need to increase the amount of time spent in that activity to achieve an antihypertensive effect; generally four or more 30-minute sessions of aerobic exercise per week will be sufficient.

The role of dietary modification in the treatment of hypertension has received a great deal of attention over the years, most of which has focused on the role of sodium. The debate over whether excessive sodium intake actually causes hypertension is unresolved.¹³ However, many persons with hypertension, children included, are "salt sensitive," and will probably benefit from a reduction in their sodium intake. Other dietary constituents that have been examined with respect to hypertension include potassium and calcium, both of which have been demonstrated to have an antihypertensive effect.^14,15 Therefore, a diet low in sodium but enriched with potassium and calcium may be even more effective than a diet that restricts sodium only. An example of such a diet is the so-called DASH (Dietary Approaches to Stop Hypertension) diet, which has been shown to have a clear blood pressure–lowering effect in adults with hypertension, even in those receiving antihypertensive medication.¹⁶ Detailed information on the DASH diet, including suggested meal plans, can be found at http://www.nhlbi.nih.gov/health/ public/heart/hbp/dash. Although this diet has not been studied specifically in children, its basic elements should be easily adaptable to the treatment of hypertensive children if used under the supervision of a registered pediatric dietitian. The DASH diet also incorporates measures designed to reduce dietary fat intake, an important strategy given the frequent presence of both hypertension and elevated lipids in children and adolescents.¹⁷

Pharmacotherapy. Deciding which children require antihypertensive drug treatment is the most crucial step in the management of pediatric patients with hypertension. As shown in Table 6, any child with symptomatic hypertension, secondary hypertension, or end-organ damage, or who fails nonpharmacologic measures, should be treated with antihypertensive medication. Other factors, such as the presence of obesity or a family history of hypertension, may also influence the decision to treat. The following quote from the second Task Force report is appropriate to keep in mind when contemplating starting a child on antihypertensive medication: "Major questions still remain unresolved with regard to the long-term effects of drug treatment on children and adolescents . . . a definite need must be established before [antihypertensive] therapy . . . is introduced during the 1st or 2nd decade of life."² Given this, consultation with a specialist experienced in managing childhood hypertension should be considered at the initiation of drug therapy.

TABLE 6
Indications for drug therapy in the hypertensive child

When medication is deemed necessary, some general principles should be followed. First and foremost, nonpharmacologic measures should be incorporated into every hypertensive child's treatment plan. As noted above, weight loss, aerobic exercise, and dietary modifications can play an important role in management. The second important principle is that drug therapy should be designed to maximize compliance and minimize adverse effects. This means that drugs with longer duration of action should be chosen over those with shorter duration, and that agents with predictable adverse effects should be avoided (diuretics in teen athletes, for example).

As with treatment of hypertension in adults, the "stepped care" approach has been recommended for children treated with antihypertensive medications.^2,18 In this approach, the dose of the initial agent chosen is increased until either the BP is controlled, the maximal dose is reached, or side effects appear; then, if BP is not controlled, a second agent of a different pharmacologic class is added and its dose increased as with the first agent, and so on. If possible, the initial agent chosen should be directed at the underlying pathophysiology of the child's hypertension; a vasodilator or diuretic would be appropriate in the case of hypertension related to acute glomerulonephritis, for example, and an angiotensin-converting enzyme (ACE) inhibitor or angiotensin-receptor antagonist would be best for a child with diabetes.

The choice of initial agent is more challenging in children with primary hypertension. Although many studies compare different antihypertensive regimens in adults, no such comparative studies have been conducted in children. Therefore, although it should be noted that recent publications have focused on calcium-channel antagonists and ACE inhibitors as suitable initial choices,^3,18 the final choice of agent remains up to the individual practitioner. Fortunately, the Food and Drug Modernization Act of 1997 has prompted numerous industry-sponsored studies of antihypertensive agents in children, and these studies are increasing the amount of pediatric dosing, efficacy, and safety information available for antihypertensive medications.¹⁹ Recommended pediatric doses for selected antihypertensive agents are listed in Table 7. Given the large number of agents on the market, it is reasonable to become familiar with one or two drugs from each of the major classes so that you can prescribe with confidence. In addition, now that pediatric data are available for some antihypertensive agents, only those drugs that have been studied in children should be prescribed by the general practitioner.

PLEASE NOTE: If you are using Internet Explorer version 6 or higher, after clicking to enlarge the graphic, click the picture icon that appears in the lower right-hand corner of the graphic.

Recent publication of the results of the ALLHAT (Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial) study, which demonstrated that diuretics are superior to other types of antihypertensive drugs,²⁰ has uncertain implications for the treatment of hypertensive children. Many pediatric authorities recommend against using diuretics as first-line agents in hypertensive children except when specifically indicated. Clearly, much more research will be needed to resolve this issue, as well as to determine what the optimal first-choice agents should be in children.

The optimal BP goal of treatment in a hypertensive child remains unknown. In adults, most authorities recommend treatment to normotension whenever possible; a goal of a lower BP is recommended for adults with underlying renal disease or diabetes. These recommendations are based on solid clinical endpoints, such as congestive heart failure or death, which fortunately do not occur often in children. This lack of hypertension-related endpoints perhaps explains the lack of consensus on treatment goals for hypertensive children. For example, the second Task Force report recommends treatment to the 90th percentile or below, whereas the Working Group report recommends reduction of BP to below the 95th percentile. It is probably appropriate to treat to below the 90th percentile if the child has secondary hypertension or hypertensive target-organ damage. If these conditions do not exist, then reduction of BP to below the 95th percentile may be sufficient. Repeat ABPM, if available, can be extremely helpful in documenting that the child's BP has been successfully lowered to the chosen goal.²¹

Important adjunctive aspects to drug therapy include ongoing monitoring of BP (especially home monitoring), surveillance for medication side effects, counseling regarding other cardiovascular risk factors, and continual emphasis on nonpharmacologic measures. Repeat laboratory testing should also be performed in selected patients. For example, because ACE inhibitors and angiotensin-receptor antagonists may cause hyperkalemia and elevation of the serum creatinine, a basic metabolic panel (electrolytes, BUN, creatinine) should be obtained seven to 10 days after initiation of therapy with agents from these classes, and every six to 12 months thereafter. Because many hypertensive children also have hyperlipidemia,¹⁷ it is appropriate to obtain repeat lipid panels at similar intervals. As noted in a recent set of guidelines issued by the American Heart Association,²² a multifaceted approach is necessary for prevention of cardiovascular disease, and such prevention should clearly start in childhood. Repeat echocardiograms should be obtained annually in all children who had LVH on their initial study and in any child whose BP fails to respond to treatment.

It may be appropriate to consider so-called step-down therapy in selected patients: an attempt at gradual reduction of medication after an extended course of good BP control. The ultimate goal here is to completely discontinue drug therapy. Children with primary hypertension, especially obese children who successfully lose weight, are the best candidates for the step-down approach. Such patients usually require continued BP monitoring after drug therapy is withdrawn, as well as continued nonpharmacologic management.

Some children will require surgery for treatment of their hypertension. Such patients are typically those with renovascular hypertension, aortic coarctation, or other secondary forms of hypertension. When one of these conditions becomes apparent, these children should be referred to a children's hospital or other tertiary center, where appropriate pediatric surgical and medical specialists are available.

Controlling hypertension early

The following points about pediatric hypertension are worth noting:

• Increased awareness of hypertension in childhood, coupled with an increase in risk factors for hypertension such as obesity, means that many more children will be found to have elevated BP than in the past.

• Careful measurement of BP and thorough evaluation of children with sustained BP elevation should allow identification of those who require treatment.

• Although outcome data for childhood hypertension do not yet exist, there has been a rapid increase in the amount of information available regarding use of antihypertensive agents in children, making it easier to treat hypertensive children with confidence.

• Usually, a combination of pharmacologic and nonpharmacologic measures will result in satisfactory control of hypertension while allowing a normal quality of life.

REFERENCES

1. The Task Force on Blood Pressure Control in Childhood: Report of the Task Force. Pediatrics 1977;59:797

2. 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

3. National High Blood Pressure Education Program Working Group: Update on the Task Force Report (1987) on High Blood Pressure in Children and Adolescents: A Working Group Report from the National High Blood Pressure Education Program. NIH Publication No. 96-3790, 1996

4. Flynn JT: Evaluation and management of hypertension in childhood. Prog Pediatr Cardiol 2001;12:177

5. Laird WP, Fixler DE: Left ventricular hypertrophy in adolescents with elevated blood pressure: Assessment by chest roentgenography, electrocardiography and echocardiography. Pediatrics 1981;67:255

6. Daniels SR, Lipman MJ, Burke MJ, et al: The prevalence of retinal vascular abnormalities in children and adolescents with essential hypertension. Am J Opthalmol 1991;111:205

7. Belsha CW, Wells TG, McNiece KL, et al: Influence of diurnal blood pressure variations on target organ abnormalities in adolescents with mild essential hypertension. Am J Hypertens 1998;11:410

8. Sorof JM, Alexandrov AV, Cardwell G, et al: Carotid artery intimal-medial thickness and left ventricular hypertrophy in children with elevated blood pressure. Pediatrics 2003;111:61

9. Sorof JM, Portman RJ: Ambulatory blood pressure monitoring in the pediatric patient. J Pediatr 2000; 136:578

10. Rocchini AP, Katch V, Anderson J, et al: Blood pressure in obese adolescents: Effect of weight loss. Pediatrics 1988;82:16

11. Pinelli L, Elerdini N, Faith MS, et al: Childhood obesity: Results of a multicenter study of obesity treatment in Italy. J Pediatr Endocrinol Metab 1999;12(Suppl 3): 795

12. Arrol B, Beaglehole R: Does physical activity lower blood pressure: A critical review of the clinical trials. J Clin Epidemiol 1992;45:439

13. Dustan HP, Kirk KA: Corcoran lecture: The case for or against salt in hypertension. Hypertension 1989;13(6 Pt 2): 696

14. Gillman MW, Hood MY, Moore LL, et al: Effect of calcium supplementation on blood pressure in children. J Pediatr 1995;127:186

15. Kawano Y, Minami J, Takishita S, et al: Effects of potassium supplementation on office, home, and 24-h blood pressure in patients with essential hypertension. Am J Hypertens 1998;11:1141

16. Appel LJ, Moore TJ, Obarzanek E, et al: A clinical trial of the effects of dietary patterns on blood pressure. N Engl J Med 1997;336:1117

17. Gidding SS: Relationships between blood pressure and lipids in childhood. Pediatr Clin N Am 1993;40:41

18. Sinaiko AR: Treatment of hypertension in children. Pediatr Nephrol 1994;8:603

19. Flynn JT: Drug therapy of childhood hypertension: Current status, future challenges. Am J Hypertens 2002; 15:30S

20. Appel LJ: The verdict from ALLHAT: Thiazide diuretics are the preferred initial therapy for hypertension. JAMA 2002;288:3039

21. Flynn JT: Impact of ambulatory blood pressure monitoring on the management of hypertension in children. Blood Press Monit 2000;5:211

22. Kavey RE, Daniels SR, Lauer RM, et al: American Heart Association guidelines for primary prevention of atherosclerotic cardiovascular disease beginning in childhood Circulation 2003;107:1562

DR. FLYNN is director, pediatric hypertension program, division of pediatric nephrology, Children's Hospital at Montefiore, Bronx, N.Y., and associate professor of clinical pediatrics, Albert Einstein College of Medicine, Bronx, N.Y. He is a consultant for Pfizer and Forest Laboratories and is on the advisory boards for Novartis and ESP Pharma.

How to determine if a blood pressure reading is normal

Anita and Clair are both12 years old. At their pre-participation sports physical examination, both had ablood pressure of 121/72.

• Anita's height plots at the 95th percentile for age. Referring to Table 1, read across the table for height percentile, then drop down to the row for 12-year-olds. Read systolic BP from the left-hand side of the table, and diastolic BP from the right-hand side. Anita's 90th percentile BP would be 122/78, and her 95th percentile BP would be 126/82. For Anita, a blood pressure of 121/72 is completely normal.

• Claire's height plots at the 10th percentile for age. Her 90th percentile BP would be 116/75, and her 95th percentile BP would be 120/79. For Claire, a BP of 121/72 represents elevated systolic blood pressure.

 

Joseph Flynn. Recognizing and managing the hypertensive child. Contemporary Pediatrics August 2003;20:38.