Hypertension in Children

HYPERTENSION IN CHILDREN

Hypertension in childhood is defined as a blood pressure reading greater than the ninetieth (901 percentile for age and sex obtained on 3 separate occasions.

INCIDENCE -

Approximately 1% of pediatric population and 3% of adolescents are hypertensive by this definition. Prevalence rates vary from 1 to 10%.

NORMAL AVERAGE BLOOD PRESSURES AT VARIOUS AGES ARE -

Age in years Systolic BP Diastolic BP (mm of Hg)

2 82-110 49-76

4 82-110 49-76

6 84-112 52-78

10 94-126 60-84

14 104-138 62-88

18 110-145 65-90

These values represent 10th & 90th percentiles

AETIOLOGY -

A)Primary hypertension-(IdiopathiclEssential hypertension) -

Accounts for only 5-10% cases. Patients usually asymptomatic & BP moderately elevated.

B)Secondary hypertension -

1) Intrinsic renal diseases

Chronic glomerulonephritis- 40% cases

Chronic pyelonephritis- 25% cases

Obstructive uropathy

Congenital lesions of kidney (Dysplastic, hypoplastic, polycystic, medullary cystic necrosis)

Renal tumors

2) Renowtscular -

Renal artery stenosis - 10% cases

Renal artery stenosis with/without aortitis

Renal vein thrombosis

3) Endocrine causes -

Pheochromocytoma, neuroblastoma

Adrenogenital syndrome

Cushing's disease, aldosteronism

4) Miscellaneous -

Drug induced e.g. ACTH, corticosteroids, amphetamines

Calcium toxicity

CURABLE FORMS OF HYPERTENSION -

Coarctation of the aorta

Remediable forms of renovascular disease

Traumatic lesions of kidney

Unilateral renal parenchymal disease

Neuroblastoma; Pheochromocytoma

Cushing's disease

Primary aldosteronism

Some cases of aortoarteritis

CAUSES OF TRANSIENT HYPERTENSION -

Renal -

Acute post-streptococcal glomerulonephritis, Hemolytic uraemic syndrome

Anaphylactoid purpura

Post renal transplant/urologic surgery

Other causes -

Administration of corticosteroids

Poliomyelitis

Guillaine-Barre syndrome

Hypematraemia

Familial dysautonomia

PATHOGENESIS -

1) In renal disease due to -

i)Sodium retention & hypervolemia.

ii)Diminution of vasodilator substances, secreted by kidneys — PGA2, kallidin, bradykinin.

iii)Elevated levels of renin- angiotensin.

2) Renovascular disease -

Narrowing of renal arteries

perfusion of kidneys

Renin secretion

Angiotensin II

Aldosterone release Na retention, plasma volume expansion & cardiac output

Vasoconstriction & T peripheral resistance

Hypertension

CLINICAL FEATURES -

Asymptomatic for years

Headache, nausea, vomiting, dizziness & irritability

Features of renal/endocrine disease

Renal damage-polyuria, polydypsia, weakness, fatigue, pallor, weight loss

Coarctation of aorta- Weak femoral pulse & BP in lower limbs less than upper limbs Li Pheochromocytoma-episodes of palpitation, sweating & flushing

Cushing's disease-plethoric facies with buffalo hump type obesity, hirsutism & abdominal striae Li CCF- extremely rare. Suggests acute glomerulonephritis or aortoarteritis if present

Fundoscopic examination may show hypertensive features

COMPLICATIONS -

Hypertensive crisis (visual disturbances, convulsions, severe nerve palsies, other neurological deficits) Li Hypertensive encephalopathy

Hypertensive nephropathy

Congestive cardiac failure

Hypertensive retinopathy

DIFFERENTIAL DIAGNOSIS -

Note-Blood pressure should be taken in both the arms & at least 1 leg.

Asymmetrical pressure with right arm pressure higher than left arm occurs in coarctation of aorta, supravalvular aortic stenosis, & obstructive aortitis.

If blood pressure is not recordable in arms but elevated in legs, the diagnosis is obstructive aortoarteritis.

Higher blood pressure in arms compared to legs occurs in coarctation & obstructive aortitis.

Renal aortic stenosis & obstructive aortitis result into an abdominal bruit (which may be audible in essential hypertension also).

Pallor combined with oedema suggests chronic renal failure.

Weight loss due to a hypermetabolic state, attacks of headache, palpitation, flushing, sweating & postural hypotension indicate

pheochromocytoma.

Obesity, hirsuitism, abdominal striae & buffalo hump suggest Cushing's syndrome.

DIAGNOSTIC INVESTIGATIONS -

Urine analysis- (Routine & Microscopy)

Chronic glomerulonephritis-Proteinuria, hyaline & granular casts.

Chronic pyelonephritis-Leukocytes & granular casts. Haematuria may be present in glomerulonephritis and haemorrhagic cystitis.

Midstream urine for urine culture

Suspected cases of urinary tract infection. Negative culture does not exclude chronic pyelonephritis.

Renal function tests

BUN, serum creatinine, serum electrolytes. Diminished creatinine clearance indicates decreased glomerular filtration rate.

IVP

Assessment of size, shape ; anomalies of calyces, pelvis & ureters.

Obstructive uropathy, renal scarring (VUR), renal mass, tumor, cysts or congenital anomalies of the kidney. Renal vein thrombosis, unilateral renal artery stenosis, etc. can be determined.

Plasma renin activity (PRA) -

Increase of PRA- in venous blood suggests renal etiology excluding primary aldosteronism. Normal PRA does not exclude a renal disease.

PRA may be normal in 20% cases of renovascular disease.

High values of PRA can occur in essential hypertension.

Urinary catecholamines

Elevated in pheochromocytoma.

X-ray chest

Notching of ribs (inferiorly) by dilated intercostal arteries in coarctation of aorta.

Renal biopsy

EM ad immunofluorescence studies.

Renal angiography -

In cases suggesting renal artery stenosis on IVP.

More than 50% luminal narrowing can lead to hypertension.

Renal USG-Renal tumors & hydronephrosis.

Renal scintiscan- Technetium (99 mmTc)

The shape of kidney, anatomy of aorta and main renal arteries.

Renogram -

Pi labeled hippuran-used for renovascular diseases. Limited value.

Concentration of renin in each renal vein -

Renin concentration determined by selective cannulation of renal veins.

A value of more than one and half times on the affected side is significant. This is done in cases with unilateral disease requiring surgery.

MANAGEMENT -

Salt restriction -

Useful measure difficult to implement. In essential hypertension, which is usually inherited, the whole familY should be advised to restrict salt in cooking. During summer with excess loss of sodium in sweat, it may not be desirable to practice salt restriction except cases with hypertensive cardiac failure.

Use of antihypertensive drugs -

1)Diuretics -

Hydrochlorothiazide- 1 to 2 mg/kg/day in 3 divided doses.

Frusemide- Preferred in patients with impaired renal function. Dose-1 to 2 mg/kg/day.

Spironolactone-2 to 3 mg/kg/day in 3 divided doses

Triamterene- 4mg/kg/day in 3-4 divided doses.

2)Beta-blockers -

Atenolo1-1 to 2 mg/kg/day single daily dose.

Propranolo1-2 to 4 mg/kg/day in 2-3 divided doses. It suppresses renin secretion and affects peripheral renal sympathetic nervous activity. Contraindicated in bronchial asthma.

Metoprolol & Labetolol (5-10 mg/kg/day) can also be used.

3)ACE inhibitors -

Lower the angiotensin levels & lead to vasodilatation.

Captopril-1.0 mg/kg/day maximum 6 mg/kg/day in 3 divided doses.

Enalapril-has lesser side effects. Use in children under evaluation.

4)Calcium channel blockers -

Cause vasodilatation by inhibiting slow inward movement of calcium in the vascular smooth muscles. Nifedipine-0.5 to 1 mg/kg/day in 3 divided doses orally. Sublingually 300-500 mcg/kg/dose. Verapamil-0.15 mg/kg iv bolus followed by 5 mcg/kg/min. infusion.

5)Vasodilators -

Cause arteriolar dilatation & increase renal blood flow but do not affect GFR. Renin secretion May increase causing sodium & water retention. Hence, diuretics to be concomitantly given.

Hydralazine-0.75 to 7 mg/kg/day in 3 divided doses.

Sodium nitroprusside- 0.5 to 8.0 mcg/kg/min infusion.

6)Miscellaneous -

Methyl dopa-10 to 40 mg/kg/day in 2 divided doses.

Clonidine-15 to 25 mcg/kg/day in 3 divided doses.

Reserpine-0.02 mg/kg/day in 1 or 2 doses & 0.07 mg/kg/day i.m.

MANAGEMENT OF HYPERTENSIVE CRISIS -

Parenteral agents used preferably.

1)Diazoxide-5mg/kg IV stat, repeat in do minutes if no response.

2)Sodium nitroprusside - 50 mg is dissolved in 500m1 of 5 % dextrose solution to give concentration of 5 micrograms/mV IV drip is started delivering 0.5 to 0.8 micrograms/kg/minute or 0.01 to 0.16 ml of above solution/kg/minute in IV drip. Dose can be titrated up to 8 microgram/14min.

3)Hydralazine-0.1 to 0.2 mg/kg IV or IM. May repeat after 6 hours.

4)Resetpine-0.07 mg/kg (maximum 2.5mg) IM.

5)Alpha-methyl dopa- 5 to 10 mg/kg (dissolved in 50m125% dextrose solution) slow IV drip.

Verapamil-iv 0.15 mg/kg bolus dose. Action starts in 1.5 minutes & continues up to 30 minutes. Continuous drip-0.005 mg/kg/minutes

6)Nifedipinefxi-0.2 to 0.7 mg sublingually.

7)Phentolamine-used in pheochromocytoma 1-2 mg IV. Effect starts in 1 minutes, peaks at 5 minutes & lasts for maximum 1 hour. [Propranolol is added after ensuring alpha-adrenergic blockage-i.e. usually 5 days in cases of pheochromocytoma]

8)Labetalol

STEPWISE TREATMENT OF ESSENTIAL HYPERTENSION -

General measures -

Changes in life style.

Diet low in salt & animal protein Reduction in weight if obese. Regular exercise.

Evaluation of blood lipids.

First drug - Diuretic

Second step in pharmacotherapeutics - Beta blocker or ACE inhibitor or calcium channel blocker

Third step - Clonidine or alpha methyldopa

Use of guanethidine & betanethidine now give up.

All patients on thiazide diuretics should be given potassium supplements (1 mcg/kg/ 24 hours of KCL liquid). They are not given if ACE inhibitors are used even if a diuretic is being given.

Families of all children on clonidine should be clearly told that sudden stoppage may result in severe rebound hypertension. The drug should be gradually tapered off.