Hypertension in Children

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Symposium on Adult Diseases in Children - February 2009

 

Tex Med. 2009;105(2):44-46.

By Tammy Camp, MD, and Deogracias Pena, MD

Introduction

As the trend in obesity becomes increasingly common in American children, the prevalence of hypertension and other health consequences of obesity are also increasing in children. The national prevalence of overweight children has increased from 4 percent to 6 percent in the early 1970s to 15 percent in 1999 and 2000. 1 Currently, the prevalence of hypertension in children is estimated to be between 2 percent and 5 percent. 2,3 While secondary hypertension is still more common, primary (i.e., essential) hypertension is becoming the leading cause of hypertension in children because of the obesity epidemic. 1,3

In 2004, the fourth report of the National High Blood Pressure Education Program (NHBPEP) Working Group provided an update in the diagnosis, evaluation, and treatment of high blood pressure in children and adolescents based on the most recent evidence. 4 Despite this report, Hansen et al found that pediatric clinicians frequently did not appropriately identify hypertension and prehypertension in children seen in their clinics even though the data to make the diagnosis were available in the children's charts. 5 This implies that though pediatricians are aware of hypertension, they do not always apply the consensus guidelines to make the diagnosis and then implement the appropriate evaluation and treatment.

 

Definition and Classification of Hypertension

According to the NHBPEP report, any child should be considered hypertensive if his or her average systolic blood pressure (SBP) and/or diastolic blood pressure (DBP) is ≥95th percentile for gender, age, and height on three or more occasions. Further, a child with blood pressure measurements between the 90th and 95th percentiles, as well as an adolescent with blood pressure ≥120/80 mm Hg, should be considered prehypertensive. Normative data for blood pressure based on gender, age, and height, including 50th, 90th, 95th, and 99th percentiles, are found in the revised tables from the NHBPEP Working Group. 4

As differences between blood pressure at the 95th and 99th percentiles is only 7 to 10 mm Hg, the NHBPEP report suggests that the clinician stage the hypertension to aid in distinguishing between mild hypertension and severe hypertension. Stage 1 hypertension is defined as blood pressure between the 95th and 99th percentiles plus 5 mm Hg, while stage 2 hypertension is defined as systolic or diastolic blood pressure >99th percentile plus 5 mm Hg.

 

Blood Pressure Measurement in Children

All children older than 3 years should have their blood pressure measured at least once during every medical visit. In addition, children younger than 3 years with a history of prematurity, very low birth weight, other neonatal complication requiring intensive care, congenital heart disease, recurrent urinary tract infections, hematuria, proteinuria, renal disease, urologic malformations, family history of renal disease, solid-organ transplant, malignancy, bone marrow transplant, treatment with drugs known to increase blood pressure, or systemic illnesses such as neurofibromatosis or tuberous sclerosis, or children with evidence of elevated intracranial pressure should have their blood pressure measured at each health care encounter. 4

Blood pressure tables are based on auscultatory measurements; the NHBPEP Working Group recommends that blood pressure levels >90th percentiles obtained with oscillometric devices be remeasured by auscultation. Measurements should be taken in the right arm with an appropriate size cuff, with systolic blood pressure determined by the onset of Korotkoff sounds and diastolic blood pressure as the disappearance of these sounds. Once elevated blood pressure is confirmed, blood pressures should be taken in all four extremities.4

The importance of multiple measurements being taken over time was well demonstrated by Sorof et al, when the first screening of children in school showed a prevalence of hypertension of 19.4 percent, followed by a decrease to 9.5 percent at the second screening and a final decrease to 4.5 percent on the third screening. 2

Ambulatory blood pressure monitoring (ABPM) has become an increasingly popular tool used for measurement of blood pressure by experts in pediatric hypertension. With ABPM, a portable blood pressure device is worn by the patient over the course of 24 hours with measurements taken at specific intervals. Although efforts to standardize interpretation of these results need to be undertaken, ABPM can be very useful in diagnosing "white-coat hypertension," a condition that refers to elevated blood pressure measurements in a clinical setting, followed by normal ABPM. 6 In addition, its use may be beneficial in the evaluation of the child presenting with left ventricular hypertrophy in the absence of another obvious cause, leading to a diagnosis of masked hypertension. 7 Furthermore, ABPM can help identify children with masked hypertension and prehypertension and can assist in the assessment of cardiovascular risk of youth with obesity and the metabolic syndrome. Prevalence of white-coat hypertension and masked hypertension was found by Stabouli to be 12.9 percent and 9.4 percent, respectively, in patients referred to a hypertension center by primary care providers. 8

 

Evaluation

Evaluation of the child or adolescent with at least three confirmed blood pressure readings >95th percentile on at least three separate occasions should be aimed initially at differentiating between primary and secondary hypertension. The history and physical examination should focus particularly on diet, sleep history, family history, risk factors, and habits such as smoking and use of alcohol or drugs.

Signs and symptoms of underlying disease should be sought. Gross hematuria, edema, and fatigue can suggest renal disease, whereas chest pain, exertional dyspnea, and palpitations are associated with heart disease. Rashes, joint swelling, and flushing are more likely to be associated with diseases of other organ systems, such as endocrinologic or rheumatologic.

A dietary and exercise history is critical, as the increased risk of hypertension in relationship to overweight is well described: Sorof et al noted a greater than fivefold increase in the prevalence of hypertension as body mass index (BMI) increased from ≤5th percentile to ≥95th percentile. Also, overweight children are more likely to be diagnosed with primary hypertension versus secondary hypertension. 9

Because blood pressure dysregulation occurring during sleep and wakefulness has been shown in children with obstructive sleep apnea, obtaining a sleep history is crucial. 10 Mindell et al describe the use of a sleep screening tool, BEARS, in which b edtime problems, e xcessive daytime sleepiness, a wakenings during the night, r egularity and duration of sleep, and s leep-disordered breathing are evaluated. 11 In addition to sleep history, other questions should focus on previous hospitalizations, trauma, and urinary tract infections.

Family history should also be considered in evaluating hypertension. Robinson et al found that a family history of hypertension was positive in 51 percent of children with primary hypertension and in 26 percent of children with secondary hypertension. 9 Other family history questions of significance should focus on diabetes, obesity, sleep apnea, renal disease, hyperlipidemia, stroke, and familial endocrinopathies.

Although the physical examination in a child with hypertension is frequently normal except for the elevated blood pressure, careful examination should be undertaken for an underlying etiology for the hypertension. Decreased blood pressure in the lower extremities compared with the upper extremities and diminished lower extremity pulses or a heart murmur may be associated with coarctation of the aorta. Growth retardation can be associated with chronic renal failure. An elevated body mass index may indicate primary hypertension. Dysmorphic features may be associated with a chromosomal abnormality. The skin should be examined closely for evidence of a neurocutaneous syndrome. An abdominal mass could imply a Wilm's tumor, neuroblastoma, or pheochromocytoma. The examiner should also look for evidence of target organ damage.

In addition to the history and physical examination, all children and adolescents with blood pressure measurements ≥95th percentile should undergo a laboratory evaluation. Because most cases of secondary hypertension in children will have a renal or renovascular cause, the laboratory evaluation should begin with blood urea nitrogen (BUN), creatinine, electrolytes, urinalysis, urine culture, complete blood count (CBC), and a renal ultrasound. These children should also have a fasting lipid panel and glucose. To assess for target organ damage, an echocardiogram and retinal exam are recommended.

Further laboratory evaluation should be conducted on the basis of the history and examination. For patients who are overweight and have blood pressure readings between the 90th and 94th percentiles, or for patients with a family history of cardiovascular disease or hypertension, a fasting lipid panel and glucose should be obtained. If these patients also have a history of diabetes mellitus or kidney disease, they should undergo echocardiogram and retinal examination.

Renovascular imaging, plasma renin determination, plasma and urine steroid levels, and plasma and urine catecholamines should be reserved for young children with stage 1 hypertension and children or adolescents with stage 2 hypertension.

 

Treatment

For children and adolescents identified with prehypertension or stage 1 hypertension, initial interventions should aim at lifestyle modifications. For children and adolescents with hypertension related to obesity, the goal should be to limit any future weight gain and to lose weight as deemed appropriate. Children and adolescents should be encouraged to limit "screen time" to less than two hours per day, while spending 60 minutes in physical activity every day.

Dietary changes should incorporate an increase in fresh fruits and vegetables daily, a decrease in sugar-containing beverages, an increase of fiber and nonfat dairy products, and a reduction of sodium. In addition to these changes, patients should be encouraged to limit portion sizes.

According to the fourth report on hypertension, for patients demonstrating symptomatic hypertension, secondary hypertension, hypertensive target-organ damage, diabetes (types 1 and 2), or persistent hypertension despite nonpharmacologic measures, initiation of an antihypertensive drug is indicated. When an antihypertensive drug is indicated, a single drug should be started. All classes of antihypertensives have been shown to reduce blood pressure in children; β-adrenergic blockers, diuretics, a ngiotensin-converting enzyme (ACE) inhibitors, calcium channel blockers, and angiotensin-receptor blockers have been studied in the pediatric population. The goal of the antihypertensive therapy should be to decrease blood pressure to <95th percentile, unless concurrent conditions such as diabetes or renal disease are present. In that case, blood pressure should be lowered to <90th percentile.

Intravenous antihypertensive therapy should be provided for children experiencing severe, symptomatic hypertension with blood pressure well above the 99th percentile. These symptoms may manifest as hypertensive encephalopathy leading to seizures.

 

Conclusion

Hypertension, less common in children than in adults, should be recognized by the primary care physician. Although the incidence of secondary hypertension in children is more common than in adults, an increasing incidence of primary hypertension is noted with the increased prevalence of obesity. Children with primary hypertension tend to be more obese and older at the time of diagnosis. 7 Furthermore, though data are lacking in the measurement of long-term outcomes of children with hypertension, primary care physicians need to become adept in evaluating and treating the disease as we await more longitudinal studies to determine the long-term morbidity of this disease process.  

 

References

  1. Ogden CL, Flegal KM, Carroll MD, Johnson CL. Prevalence and trends in overweight among U.S. children and adolescents, 1999-2000. JAMA . 2002;288(14):1728-1732.
  2. Sorof JM, Lai D, Turner J, Poffenbarger T, Portman RJ. Overweight, ethnicity, and the prevalence of hypertension in school-aged children. Pediatrics. 2004;113(3 pt 1):475-482.
  3. Moore WE, Stephens A, Wilson T, Wilson W, Eichner JE. Body mass index and blood pressure screening in a rural public school system: the Healthy Kids Project. Prev Chronic Dis. 2006;3(4):A114.
  4. National High Blood Pressure Education Program Working Group on High Blood Pressure in Children and Adolescents. The fourth report on the diagnosis, evaluation and treatment of high blood pressure in children and adolescents. Pediatrics. 2004;114(2 suppl 4th report):555-576.
  5. Hansen ML, Gunn PW, Kaelber DC. Underdiagnosis of hypertension in children and adolescents. JAMA. 2007;298(8):874-879.
  6. Lurbe E, Sorof JM, Daniels SR. Clinical and research aspects of ambulatory blood pressure monitoring in children. J Pediatr. 2004;144(1):7-16.
  7. O'Brien E. Unmasking hypertension. Hypertension. 2005;45(4):481-482.
  8. Stabouli S, Kotsis V, Toumanidis S, Papamichael C, Constantopoulos, Zakopoulos N. White-coat and masked hypertension in children: association with target-area damage. Pediatr Nephrol. 2005;20:1151-1155.
  9. Robinson RF, Batisky DL, Hayes JR, Nahata MC, Mahan JD. Body mass index in primary and secondary hypertension. Pediatr Nephrol. 2004;19(12):1379-1384.
  10. Amin RS, Carroll JL, Jeffries JL, et al. Twenty-four hour ambulatory blood pressure in children with sleep-disordered breathing. Am J Respir Crit Care Med. 2004;169(8):950-956.
  11. Mindell JA, Owens JA. A Clinical Guide to Pediatric Sleep: Diagnosis and Management of Sleep Problems. Philadelphia, PA: Lippincott, Williams & Wilkins; 2003:10.

 

Dr. Camp is an assistant professor of clinical pediatrics at Texas Tech University Health Sciences Center in Lubbock and associate program director of the school's pediatric residency program. Dr. Pena is the medical director of pediatric nephrology, dialysis, and transplantation at Cook Children's Hospital in Fort Worth.

 

 

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