Definition
For adults, the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7 Report, 2003) has recommended the following classification of blood pressure (BP) levels. BP level of 120/80 mm Hg, previously considered normal, is now classified as prehypertension; levels lower than 120/80 are now considered normal. Systolic pressure of 140 mm Hg and greater or diastolic pressure of 90 mm Hg and greater are now considered hypertension. Hypertension is further classified as stage 1 and stage 2 depending on the level of abnormalities ( Table 28-1 ).
| BP Classification | Adults ∗ | Children † and Adolescents ∗ | |
|---|---|---|---|
| Systolic BP (mm Hg) | Diastolic BP (mm Hg) | ||
| Normal | <120 | <80 | <90th percentile |
| Prehypertension | 120–139 | 80–89 | 90th–95th percentile |
| Stage 1 hypertension | 140–159 | 90–99 | 95th–99th percentile |
| Stage 2 hypertension | ≥160 | ≥100 | ≥5 mm Hg + 99th percentile value |
∗ Adapted from Chobanian AV, Bakris GL, Black HR, et al: The seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: The JNC 7 report. JAMA 21:2560-2572, 2003.
† Pediatric classification is according to the Fourth Report on the Diagnosis, Evaluation, and Treatment of High Blood Pressure in Children and Adolescents. Pediatrics 111:555-576, 2004.
In children, hypertension is defined statistically because BP levels vary with age and gender and because outcome-based data are not available for children. The Fourth Report of the National High Blood Pressure Education Program (NHBPEP) Working Group on High Blood Pressure in Children and Adolescents (2004) has recommended the following definition (also see Table 28-1 ).
- 1.
Hypertension is defined as systolic or diastolic pressure levels that are greater than the 95th percentile for age and gender on at least three occasions. As in adults, adolescents with BP levels of 120/80 mm Hg or above by auscultatory method are considered hypertensive even if they are below the 95th percentile.
- 2.
Prehypertension is defined as an average systolic or diastolic pressure between the 90th and 95th percentiles for age and gender.
- 3.
When the BP reading is above the 95th percentile, one further classifies the hypertension into stages 1 and 2 as follows.
- a.
Stage 1 hypertension is present when BP readings are between the 95th and 99th percentiles.
- b.
Stage 2 hypertension is present when BP readings are 5 mm Hg or more above the 99th percentile values.
- a.
- 4.
White-coat hypertension is present when BP readings in health care facilities are greater than the 95th percentile but are normotensive outside a clinical setting. This condition may not be as benign as once thought to be, and regular follow-up is now recommended. This topic is discussed further later in this chapter.
Normative Blood Pressure Standards
A prerequisite to the use of the above definition for pediatric hypertension is the availability of reliable normative BP standards. An unfortunate part of the problem is that there are no reliable evidence-based BP standards for children. The BP tables recommended by the Working Group of the NHBPEP are not as good as they were made to believe because (1) the BP data are not derived by the methodology recommended by the working group, (2) expressing BP levels by age and height percentiles is statistically unsound and unjustified, and (3) additional computation of BP levels by height percentile on such highly variable office BP readings are impractical and unproductive for busy practitioners (see Blood Pressure Measurement in Chapter 2 for further discussion). The NHBPEP’s statistical efforts on unscientifically obtained data do not improve their validity.
In addition, it is important to know that the BP standards of the NHBPEP cannot be used when BP is measured by an oscillometric device. BPs measured by the auscultatory method are not interchangeable with those measured by the oscillometric method, which is being used in increased frequency. In San Antonio Children’s Blood Pressure Study (SACBPS) using both the auscultatory and an oscillometric device (Dinamap Model 8100), BP levels obtained by Dinamap, an oscillometric device, were on average 10 mm Hg higher for the systolic pressure and 5 mm Hg higher for the diastolic pressures than those obtained by the auscultatory method ( Park et al, 2001 ). Therefore, when BPs are obtained by an oscillometric device, one should not use the BP standards provided by the NHBPEP, which are based on the auscultatory method. Only normative BP standards by Dinamap Monitor are those from the SACBPS ( Park et al, 2005 ), and they are presented in Appendix B ( Table B-6 , Table B-7 ) according to age and gender.
Kaelber et al (2009) have recommended a simplified table of BP levels according to age and gender (without height percentiles), above which further evaluation should be carried out for possible hypertension (see left half of Table 28-2 ). This is a more practical approach because in some BP screening sites, height is not always measured and because the inclusion of height percentile in BP evaluation has no statistical validity (as discussed in Chapter 2 ). Auscultatory BP levels presented in Table 28-2 agree very closely with the normative auscultatory standards reported by the SACBPS ( Park et al, 2005 ). Because BP levels obtained by an oscillometric device are not interchangeable with those obtained by the auscultatory method, BP levels in the prehypertensive range by the oscillometric (Dinamap) method ( Park et al, 2005 ) are shown in the right half of Table 28-2 for the same reasons.
| Auscultatory ∗ | Oscillometric † | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Age (yr) | Male | Female | Age (yr) | Male | Female | ||||
| Syst | Diast | Syst | Diast | Syst | Diast | Syst | Diast | ||
| 3 | 100 | 59 | 100 | 61 | 3 | ||||
| 4 | 102 | 62 | 101 | 64 | 4 | ||||
| 5 | 104 | 65 | 103 | 66 | 5 | 116 | 70 | 115 | 69 |
| 6 | 105 | 68 | 104 | 68 | 6 | 118 | 70 | 116 | 69 |
| 7 | 106 | 70 | 106 | 69 | 7 | 119 | 70 | 117 | 70 |
| 8 | 107 | 71 | 108 | 71 | 8 | 120 | 71 | 119 | 70 |
| 9 | 109 | 72 | 110 | 72 | 9 | 122 | 71 | 120 | 71 |
| 10 | 111 | 73 | 112 | 73 | 10 | 123 | 72 | 122 | 71 |
| 11 | 113 | 74 | 114 | 74 | 11 | 125 | 72 | 123 | 72 |
| 12 | 115 | 74 | 116 | 75 | 12 | 128 | 72 | 124 | 72 |
| 13 | 117 | 75 | 117 | 76 | 13 | 130 | 72 | 126 | 73 |
| 14 | 120 | 75 | 119 | 77 | 14 | 130 | 73 | 126 | 73 |
| 15 | 120 | 76 | 120 | 78 | 15 | 130 | 73 | 127 | 74 |
| 16 | 120 | 78 | 120 | 78 | 16 | 130 | 73 | 127 | 74 |
| 17 | 120 | 80 | 120 | 78 | 17 | 130 | 73 | 127 | 74 |
| ≥18 | 120 | 80 | 120 | 80 | |||||
∗ From Kaelber DC, Pickett F: Simple table to identify children and adolescents needing further evaluation of blood pressure. Pediatrics 123(6):e972, 2009. For adolescents age 14 years and older, systolic pressure of 120 mm Hg is in prehypertensive range, as in adults.
† Data from Park MK, Menard SW, Schoolfield J: Oscillometric blood pressure standards for children. Pediatr Cardiol 26:601-607, 2005. These values were obtained by Dinamap model 8100 and in general fall between the 90th and 95th percentiles of blood pressure (prehypertension range). A systolic blood pressure of 130 mm Hg has been chosen for male teens 14 to 17 years old in this table.
Cause
Hypertension is classified into two general types, essential (or primary) hypertension, in which a specific cause cannot be identified, and secondary hypertension, in which a cause can be ( Box 28-1 ).
- 1.
The exact prevalence of essential hypertension in children and adolescents is not known. It is estimated that about 60% of pediatric patients with hypertension have essential hypertension. Among the patients with essential hypertension 75% of them are obese. Thus, the most common cause of pediatric hypertension appears to be obesity; about 10% to 30% of obese children are reported to have hypertension.
- 2.
Among patients with secondary hypertension, more than 90% of the cases are caused by three conditions: renal parenchymal disease and renovascular diseases (both accounting for 70%) and coarctation of the aorta (COA) (20%). Fewer than 10% of secondary hypertension is caused by endocrine and other disorders.
- 3.
In newborns, the causes of hypertension may include renal artery thrombosis, congenital renal malformation, and COA. Transient hypertension may be found in neonates with bronchopulmonary dysplasias, which resolves when oxygenation improves.
Renal
Renal parenchymal disease
Glomerulonephritis, acute and chronic
Pyelonephritis, acute and chronic
Congenital anomalies (polycystic or dysplastic kidneys)
Obstructive uropathies (hydronephrosis)
Hemolytic-uremic syndrome
Collagen disease (periarteritis, lupus)
Renal damage from nephrotoxic medications, trauma, or radiation
Renovascular disease
Renal artery disorders (e.g., stenosis, polyarteritis, thrombosis)
Renal vein thrombosis
Cardiovascular
Coarctation of the aorta
Conditions with large stroke volume (patent ductus arteriosus, aortic insufficiency, systemic arteriovenous fistula, complete heart block) (these conditions cause only systolic hypertension)
Endocrine
Hyperthyroidism (systolic hypertension)
Excessive catecholamine levels
Pheochromocytoma
Neuroblastoma
Adrenal dysfunction
Congenital adrenal hyperplasia
11-β-Hydroxylase deficiency
17-Hydroxylase deficiency
Cushing’s syndrome
Hyperaldosteronism
Primary
Conn’s syndrome
Idiopathic nodular hyperplasia
Dexamethasone-suppressible hyperaldosteronism
Secondary
Renovascular hypertension
Renin-producing tumor (juxtaglomerular cell tumor)
Hyperparathyroidism (and hypercalcemia)
Neurogenic
Increased intracranial pressure (any cause, especially tumors, infections, trauma)
Poliomyelitis
Guillain-Barré syndrome
Dysautonomia (Riley-Day syndrome)
Drugs and chemicals
Sympathomimetic drugs (nose drops, cough medications, cold preparations, theophylline)
Amphetamines
Corticosteroids
Nonsteroidal antiinflammatory drugs
Oral contraceptives
Heavy-metal poisoning (mercury, lead)
Cocaine, acute or chronic use
Cyclosporine
Thyroxine
Tacrolimus
Miscellaneous
Hypervolemia and hypernatremia
Stevens-Johnson syndrome
Bronchopulmonary dysplasia (newborns)
In general, children with essential hypertension are older than 10 years of age, have mild hypertension, and are often obese. Secondary hypertension is suggested by a younger age, levels of hypertension (varying from mild to severe, especially stage 2 hypertension), and presence of clinical signs that suggest systemic conditions. Children with secondary hypertension are rarely obese and are often less than normal height. Table 28-3 lists the common causes of hypertension by age group in children. Box 28-1 lists the causes of secondary hypertension.
| Age Group | Causes |
|---|---|
| Newborns | Renal artery thrombosis, renal artery stenosis, congenital renal malformation, COA, bronchopulmonary dysplasia |
| <6 yr | Renal parenchymal disease, COA, renal artery stenosis |
| 6–10 yr | Renal artery stenosis, renal parenchymal disease, primary hypertension |
| >10 yr | Primary hypertension, renal parenchymal disease |
Diagnosis and Workup
Steps to Confirm the Diagnosis
- 1.
The diagnosis of hypertension relies on accurate BP measurement and comparing the reading with reliable BP standards. In evaluating for possible diagnosis of hypertension, it is very important to remember that (a) the most common cause of high BP readings, especially of a single BP reading, in a health care facility is anxiety, called the white-coat phenomenon, and (b) BPs measured by the auscultatory and oscillometric methods are significantly different and thus are not interchangeable (as mentioned earlier). The following is one way of handling a case of high BP reading in the office setting.
- a.
If an abnormal reading is the result of single reading, two additional measurements should be made to help reduce the effects of anxiety associated with a visit to the doctor’s office.
- b.
If BP is still high, a repeat set of three readings at the end of the office visit may help identify some of the children with the white-coat phenomenon.
- c.
Even if these BP readings are still high, a possibility of white-coat hypertension still exists. The diagnosis of hypertension should not be made until one confirms persistently elevated BP levels greater than the 95th percentile on three or more separate office visits over a period of time.
- d.
One should consider ways to identify cases of white coat hypertension by measuring BPs outside the health care facility.
- (1)
Some physicians advocate the use of the ambulatory BP measurement to rule out white-coat hypertension. Ambulatory BP measurement is costly, and it reflects BP readings on a single day; BPs vary from day to day.
- (2)
Having reliable school nurses to take daily BP for 3 to 4 weeks may be a cost-effective way to get the same information.
- (3)
Home BP monitoring can be an option. For adult patients, new position papers from the United States and Europe recommend home BP monitoring as a routine part of diagnosis and management of hypertension. They recommend recording an average of two (or three) BP readings taken in the morning and at night for 1 week, with a total of at least 12 readings being averaged to make clinical decisions. It is reasonable to try home BP measurement in children under certain circumstances using a protocol similar to the one described for adults.
- (4)
For home BP monitoring, the monitor should be checked for its accuracy, and the patient should be taught correct measurement technique and correct BP cuff size. Wrist monitors are not acceptable because the readings will reflect peripheral amplification of systolic pressure. In evaluating home BP readings, one should not use BP standards by NHBPEP, which are based on the auscultatory method. One may use the oscillometric BP data from the San Antonio Children’s Blood Pressure Study. Appendix B provides normative oscillometric BP values ( Table B-6 for boys; Table B-7 for girls).
- (1)
- a.
- 2.
If multiple BP readings obtained outside the health care facility show persistently elevated BP levels above the 95th percentile most of the time, one could make a tentative diagnosis of hypertension and proceed with initial investigation for hypertension (as described below).
- 3.
If the repeated BP measurements fall between the 90th and 95th percentiles (prehypertension), the patient should be followed on a regular basis (every 3 to 6 months) with repeat BP measurements.
- 4.
When the diagnosis of hypertension is established:
- a.
One should evaluate the history (present, past, and family), perform careful physical findings, and proceed with initial investigation to look for the cause of hypertension.
- b.
The initial investigation should include urinalysis, serum electrolytes, renal function tests, uric acid, and electrocardiography (ECG) or echocardiography. The diagnosis of essential hypertension is made when the cause of hypertension is not found in a hypertensive patient older than 10 years of age.
- c.
One should also assess additional cardiovascular risk factors, including obesity, which is the most common associated finding in children with essential hypertension. Currently recognized cardiometabolic risk factors include:
- (1)
Family history of premature cardiovascular disease
- (2)
Obesity
- (3)
Dyslipidemias, such as hypercholesterolemia, hypertriglyceridemia, and low levels of high-density lipoprotein cholesterol (<40 mg/100 mL)
- (4)
Cigarette smoking
- (5)
Diabetes mellitus or prediabetic state
- (6)
Physical inactivity
- (1)
- a.
History
Past and Present History
- 1.
Present history
- a.
Most children with mild hypertension are asymptomatic, and hypertension is diagnosed as the result of routine BP measurement, highlighting the importance of accurate measurement of BP.
- b.
Children with acute severe hypertension may be symptomatic, such as that seen with acute glomerulonephritis (with headache, dizziness, nausea and vomiting, irritability, or personality changes). Occasionally, neurologic manifestations, congestive heart failure, renal dysfunction, and stroke may be the presenting symptoms.
- c.
Weakness and muscle cramp from hypokalemia may be seen with primary aldosteronism.
- d.
A history of palpitation, headache, and excessive sweating may suggest increased catecholamine levels.
- e.
Tachycardia with systolic hypertension may suggest hyperthyroidism or catecholamine excess.
- a.
- 2.
Neonatal: Use of umbilical artery catheters (a possible cause of renovascular hypertension)
- 3.
Cardiovascular: History of COA or surgery for it
- 4.
Renal: History of obstructive uropathies; urinary tract infection; and radiation, trauma, or surgery to the kidney area
- 5.
Medications: Corticosteroids, amphetamines, antiasthmatic drugs, cold medications, oral contraceptives, nephrotoxic antibiotics (e.g., aminoglycosides, sulfonamides, amphotericin B, trimethoprim, and others), cyclosporin, cocaine use, excessive dose of thyroxin, ingestion of large quantity of licorice. (Licorice inhibits 11β-hydroxysteroid dehydrogenase with a resulting increase in cortisol levels and producing hypokalemia.)
- 6.
Habits: Smoking or consumption of excessive amount of coffee or tea
Family History
- 1.
Essential hypertension, atherosclerotic heart disease, and stroke
- 2.
Familial or hereditary renal disease (polycystic kidney, cystinuria, familial nephritis)
Physical Examination
- 1.
Accurate measurement of BP is essential.
- 2.
Complete physical examination also is essential, with emphasis on the following:
- a.
Delayed growth (renal disease)
- b.
Bounding peripheral pulse (patent ductus arteriosus or aortic regurgitation)
- c.
Weak or absent femoral pulses or BP differential between the arms and legs (COA). In normal children, systolic pressure in the lower limbs is more than 5 to 10 mm Hg higher than that in the upper limbs.
- d.
Abdominal bruits (renovascular)
- e.
Tenderness over the kidney (renal infection)
- a.
- 3.
Children’s weight status, including body mass index percentile, should be obtained because obesity is a common cause of essential hypertension. Children with secondary hypertension from renal diseases are rarely obese, although those with hypertension from adrenocortical disorders may be obese.
Initial Investigation
- 1.
The initial investigations should be directed toward detecting renal parenchymal disease and COA and therefore include the following ( Table 28-4 ).
- a.
Urinalysis: Abnormal urinalysis with red blood cells or white blood cells suggests nephritis or infectious processes. Urine culture is indicated if urinalysis suggests infectious processes. Urinalysis is normal in essential hypertension, renovascular hypertension, and endocrine hypertension.
- b.
Serum electrolytes: Low potassium levels suggest aldosterone excess, either from primary aldosteronism or secondary hyperaldosteronism (including renovascular hypertension). Serum electrolyte changes also occur in endocrine disorders causing hypertension; hypokalemia may be seen with Cushing’s syndrome or certain (not all) types of congenital adrenal hyperplasias (11-β hydroxylase deficiency and 17-hydroxylase deficiency). Hypercalcemia suggests hyperparathyroidism.
- c.
Blood urea nitrogen (BUN) and creatinine: Abnormal values suggest renal parenchymal or renovascular disease, although renal function is usually not affected in renovascular hypertension. Normal BUN and creatinine do not rule out renovascular hypertension.
- d.
Uric acid level: Uric acid level above 5.5 mg/dL was found in 89% of subjects with primary hypertension, 30% of children with secondary hypertension, and 0% of children with white-coat hypertension and normal control participants. This finding suggests that uric acid level might have a role in the pathogenesis of primary hypertension ( Feig et al, 2003 ). Furthermore, there is independent association between uric acid level and the severity of hypertension.
- e.
ECG, chest radiographs, and echocardiography: Echocardiography is useful in ruling out COA and evaluating end-organ damage, such as left ventricular (LV) mass.
- a.
