CHILDHOOD HYPERTENSION

Systemic hypertension in childhood is defined as the systolic or diastolic blood pressure (SBP/DBP) exceeding 95^th percentile for age, sex and height-specific normal values on at least three occasions, 1-3 weeks apart for children lt; 13 years.

Table 17.36 defines and classify severity of hyper­tension in children according to the latest American Academy of Pediatrics (AAP) Guidelines 2017, based on age, sex and height related norms, which can be obtained using the calculator available at https://www.mdcalc.com/ calc/4052/aap-pediatric-hypertension-guidelines.

Prevalence of hypertension in all pediatric age groups is estimated to be ~2-5%. Unlike adults, over 90% cases of hypertension in children are secondary and need thorough diagnostic workup to identify underlying cause. However in recent years, primary or idiopathic hypertension is being increasingly recognized in obese adolescents (~15-20%).

Etiology: Renal or renovascular disease is the leading cause of childhood HT, whether transient or permanent. While gt;90% of cases with transient hypertension are due to post-streptococcal glomerulonephritis (Table 17.37), chronic renal diseases are responsible for ~3/4^th cases of persistent hypertension (Table 17.38).

Family history is common in cases of primary hyper­tension with possible multifactorial etiology involving genetic and environmental factors.

Clinical manifestations of hypertension depend on its severity, chronicity and underlying cause. Essential hypertension in children is usually mild and asympto­matic, detected on routine examination. Secondary hypertension may present with features of:

• Underlying causes, e.g. renal disease (growth failure, edema, abdominal mass), vascular disease (unequal peripheral pulses, bruits) adrenal disease (obesity, virilization) or tumors (weight loss, abdominal mass), etc.

• Intracranial hypertension, e.g. headache, vomiting, dizziness, etc. or hypertensive encephalopathy, e.g.

*but less than stage II hypertension (gt;95^thgt;95^th percentile + 12 mm Hg)

TABLE 17.37: Causes of transient hypertension

Renal causes

• Acute glomerulonephritis

• Hemolytic-uremic syndrome

• Acute pyelonephritis

• Renal trauma/surgery

Neurological causes

• Raised ICP: Encephalitis

• Guillain-Barre syndrome

• Poliomyelitis

Others:

• Drugs: Steroids, sympathomimetics

• Dyselectrolytemia: Hypernatremia, hypercalcemia

TABLE 17.38: Causes of persistent hypertension

• Renal causes (gt;75%)

- Chronic glomerulonephritis (~ 40%)

- Chronic pyelonephritis (~ 25%)

- Congenital anomalies, e.g. polycystic kidney*

- Obstructive uropathy*#8725;vesicouretric reflux

- Renal tumors

- Connective tissue disorders, e.g. SLE, HSP

• Reno-vascular (10-20%)

- Renal artery stenosis*

- Renal vein thrombosis*

• Vascular (2-3%)

- Coarctation of aorta*

- Aorto-arteritis

- Vasculitis syndromes: Henoch-Schonlein purpura

• Endocrinal (lt;1%)

- Cushing syndrome, congenital adrenal hyperplasia

- Hyperaldosteronism

- Pheochromocytoma

- Neural-crest tumors, e.g. neuroblastoma

• CNS disorders (lt;1%)

- #8593;ICP: Brain tumors, hydrocephalus

- Familial dysautonomia

• Essential or idiopathic (lt;10%)

*Common causes in newborns and early infancy

altered sensorium, seizures, neurological deficits, diplopia and fundal changes.

• Cardiovascular stress, e.g. epistaxis, cardiomegaly, CCF or renal failure.

Fundus examination is essential in all cases and important retinal changes in hypertension include: (a) generalized constriction of arterioles, (b) retinal edema, (c) flame-shaped hemorrhages, (d) cotton-wool spots denoting retinal infarcts, and (e) papilledema.

of long-standing hypertension, e.g. thick vessels with silver-wire or copper-wire appearance are rare in children.

Diagnosis of hypertension involves a two-step process—(a) confirming its presence, and (b) etiological diagnosis.

Step I. Screening and confirmation of hypertension requires repeated BP measurements as follows:

• All children gt; 3 years of age should undergo annual BP measurement, more frequently if are at-risk for essential hypertension (family history, obesity) or have systemic illnesses known to cause secondary hypertension. Children lt;3 years also need regular BP measurements, if are at risk for secondary hypertension.

• Automated BP measurement devices work on oscillometric principle and tend to overestimate BP. These devices can be used for screening purpose but abnormal values must be confirmed manually by auscultatory method. As mercury-based sphygmoma­nometers are being phased out due to environmental concerns, a digital or aneroid device may be used.

• AAP guidelines 2017 also provide for age-and sex- related cut-off values for screening BP in children of median stature (Table 17.39), to identify children who need detailed evaluation.

• BP should be recorded in comfortable setting in right arm, with appropriate cuff-size (bladder width ~ 40%

and bladder length ~80-100% of arm circumference). Normally, a cuff size of 4?8 cm, 6?12 cm, 9?18 cm and 10?24 cm is required for newborn, infant, child and adolescent, respectively. Child must be asked to rest for 5-10 minutes before taking BP and at least 2 reading must be recorded during each occasion.

• BP should be recorded by ‘auscultatory method', with appearance of first Korotkoff sound as indicator of systolic BP and fifth Korotkoff sound (or muffling of fourth Korotkoff sound) as indicator of diastolic BP. In infants, BP may be recorded by Doppler or ‘flush method'.

Flush method is useful to determine the average of systolic and diastolic BP. The limb is elevated above the couch till the distal part appears blanched due to drainage of blood. A cuff is then applied to the wrist/ ankle and pressure is elevated above the expected systolic pressure. When deflated slowly (5 mm Hg/ second), the pressure at which the hand/ foot appears flushed indicates average pressure.

• At least three readings on different occasions, mini­mum one week apart (except in very severe cases) should exceed 95^th percentile for diagnosis of hyper­tension (gt;90^th percentile for diagnosis of elevated BP).

• Ambulatory BP monitoring is recommended in cases with elevated blood pressure category for gt;1 year or stage 1 hypertension on three clinical visits.

• In hypertensive children, BP should also be recorded in lower limbs. Normal BP in lower limbs is 10-15 mm Hg higher than in upper limbs, due to more muscle mass and peripheral resistance. In coarctation of aorta or aortoarteritis (Takayasu disease), BP in lower limbs is normally less than in upper limbs.

Step II. Etiological diagnosis depends on—(a) detailed history and review of earlier case records, whether hypertension is transient or persistent, (b) physical examination for features of causative disease and (c) relevant investigations (Table 17.40), depending on probable etiology. Plasma renin activity (PRA) is a useful basic investigation in unexplained hypertension that differentiates renal or renovascular hypertension (increased PRA) from other causes (normal PRA).

Children with primary hypertension are usually older than gt;6 years, overweight, have a family history of hypertension and have no obvious cause of secondary hypertension. They should also be screened for HbA₁C, lipid profile, serum creatinine and liver enzymes.

Echocardiography is recommended in all cases to assess the target organ damage, before starting pharmacotherapy.

Management of hypertension aims to keep the BP consistently lt;90^th percentile, by (a) Specific anti­hypertensive therapy, (b) Treatment of underlying cause, e.g. surgical intervention in correctible renal, vascular

TABLE 17.40: Investigations in a hypertensive child

Base-line investigations

• Urinalysis sp. for hematuria, proteinuria

• Renal function tests, e.g. BUN, creatinine

• S. electrolytes

• Renal USG sp. for cong. anomalies, obstructive uropathy

• X-ray chest sp. for pulmonary edema, notching of ribs

• ECG sp. for LVH, ECHO for CoA

• Selective investigations

• Suspected renal or renovascular cause:

- Plasma renin activity (PRA)

- ASLO, C3 for acute nephritis

- Uroimaging studies, e.g. IVP, MCU, renal scan

- Renovascular studies, e.g. Doppler, angiography

- Renal biopsy

• Suspected vascular disease

- Aortography/digital substraction angiography

- P-ANCA and c-ANCA for vasculitis

• Suspected endocrinal cause:

- Urine/plasma catecholamines (Pheochromocytoma)

- MIBG scan, CT/MRI (Neuroblastoma)

- Cortisol challenge tests (Cushing syndrome)

- Urinary 17-OH/ketosteroids (Cong. adrenal hyperplasia)

- S. aldosterone (Hyperaldosteronism)

or neoplastic disorders and (c) non-pharmacological methods, e.g. salt-restricted diet, weight reduction and exercise, which are more useful in essential than secondary HT and hence, of limited value in children.

Many anti-hypertensive agents are available for pediatric use (Table 17.41) and the choice depends on the cause and severity of hypertension. Continuous BP monitoring is necessary to modify the choice of drug, route of administration and their dosage/ frequency. Diuretics are needed in almost all cases. Some special considerations in hypertensive therapy are as follows:

• Hypertensive Crisislencephalopathy is a serious medical emergency that needs aggressive, quick­acting antihypertensive therapy with IV sodium nitroprusside (0.5-0.8 #956;g#8725;kg#8725;min) or IV Labetalol (0.2-2.0 mg/kg/hour) or IV Esmolol (100-500 #956;g#8725; kg#8725;min) or IV Nicardipine (1-3 #956;g#8725;kg#8725;min) along with diuretics.

Hypertension due to renal disease is usually associated with high plasma renin activity, and hence, best treated with ACE-inhibitors, e.g. captopril or enalapril, along with diuretics. Calcium channel blockers, e.g. amlodipine and #946;-blockers, e.g. Propranolol may also be used in these cases. ACE inhibitors should be avoided till renovascular cause is ruled out.

Hypertension due to neural crest tumors, e.g. neuro­blastoma or pheochromocytoma, is usually associated

TABLE 17.41: Commonly used antihypertensive drugs in children

with sympathetic overactivity and hence, best treated with combination of an #945;-blocker, e.g. phentolamine or Prazosin and a #946;-blocker, e.g. Atenolol or Labetalol.

• Primary hypertension or persistent hypertension due to uncorrectable causes needs a step-wise approach to achieve sustained control, starting with—(a) non- pharmacological measures and diuretics in mild cases,

(b) addition of an ACE-inhibitor or #946;-blocker in more moderate cases, and lastly, (c) multi-drug therapy with #946;-blockers, ACE-inhibitor and calcium-channel blocker, e.g. amlodipine. Centrally acting clonidine or #946;-blocker Prazosin are rarely used in refractory cases. Number of drugs, their doses and frequency needs to be frequently modified, depending on the control of BP.

American Academy of Pediatrics guidelines (2017) recommends a step-wise approach for management of primary or essential hypertension (Table 17.42).

Prognosis of secondary HT depends upon the underlying cause, duration/severity, and response to specific therapy. While hypertensive encephalopathy and LVF are common causes of immediate mortality, persistent moderate HT may lead to secondary organ damage after many years, e.g. cardiomyopathy, retinopathy

LSM: Life style modifications, ABPM: Ambulatory BP monitoring *After excluding secondary causes

and nephropathy. Whether children with essential hypertension continue to have hypertension in adulthood, is uncertain.

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