THE EGYPTIAN SOCIETY OF PEDIATRIC ALLERGY AND IMMUNOLOGY

SYSTEMIC HYPERTENSION IN PEDIATRICS

How to measure the arterial blood pressure?

Blood pressure should be measured with a standard clinical sphygmomanometer, using the stethoscope placed over the brachial artery pulse, proximal and medial to the cubital fossa and approximately 2 cm above the cubital fossa. The appropriate cuff should have a bladder width that is approximately 40% of the child’s arm circumference when measured at a point midway between the acromion and the olecranon and it usually covers 80-100% of the arm circumference.

Blood pressure should be measured after 3-5 minutes of rest in the seated position with the cubital fossa at heart level. Infants and toddlers may be supine. The cuff should be inflated to a pressure of 20-30 mmHg above systolic blood pressure with a cuff deflation rate of 2-3 mmHg/sec. It should be recorded at least twice on each occasion.

Systolic blood pressure is determined by the onset of the ‘tapping’ Kortokoff sounds. The definition of the diastolic blood pressure is changed from muffling of the K sounds (the 4^th Kortokoff sound) in children under 13 years old to the disappearance of the sounds (the 5^th Kortokoff sound) in children of all ages.

When to diagnose systemic hypertension?

Hypertension is defined as an average systolic or diastolic blood pressure of greater than or equal to the 95^th percentile for age, sex, weight and height of the patient measured at least on 3 separate occasions taken over weeks to months.

High normal blood pressure is defined as an average systolic or diastolic blood pressure of greater than or equal to the 90^th percentile but less than the 95^th percentile.

Blood pressure indicating hypertension

Etiology of hypertension according to age

Evaluation of the child with hypertension:

1-        History:

Ask about

           ·      Family history of hypertension

           ·      Symptoms of nausea, headache, irritability, failure to thrive and deterioration of school performance, blurring of vision.

           ·      Heart disease

           ·      Symptoms indicating renal or metabolic abnormalities

           ·      Current medications (steroids)

           ·      Cerebral stroke (coma, convulsions)

           ·      Use of an umbilical catheter in the newborn

2-        Examination: (use appropriate-sized blood pressure cuff)

           ·      Blood pressure and pulses should be taken in all four extremities (differential pulses or differences in blood pressure between upper and lower extremities suggest coarctation of the aorta)

           ·      In the abdominal examination note the presence and size of both kidneys. An abdominal bruit suggests renal artery stenosis.

           ·      Note edema, thyroid size, hirsutism, striae and other signs of endocrine disorder.

           ·      Note signs of hypertensive encephalopathy such as seizures, stroke, altered mental status and focal neurological signs.

           ·      Perform a thorough fundoscopic examination looking for arteriovenous kinking, tortuosity, hemorrhage or papilledema.

Normal values of BP according to age

3-        Assess the severity of hypertension:

4-        Performance of basic diagnostic evaluation:

5-        Plan of therapy:

A- Non-pharmacologic therapy (initial management):

                      ·    Weight reduction for obese patients (may result in up to 5-10 mmHg reduction in systolic pressure and 5 mmHg reduction in diastolic pressure)

                      ·    Decrease Na intake (lower pressure by about 5 mmHg) by decreasing salt intake in all types of food.

                      ·    Change in the lifestyle and decrease the stress.

                      ·    Discourage cigarette smoking and alcohol in the family.

                      ·    Avoid (stimulant medications, sympathomimetics, amphetamines, steroids and decongestants)

B-       Pharmacologic therapy (for selected patients with essential hypertension and those with 2^ry hypertension)

1-        Treatment of acute severe hypertension (hypertensive crisis) by I.V. drugs:

It is a serious condition which may lead to hypertensive encephalopathy or heart failure so urgent therapy is needed with the following rules:

             ·    Select an agent with a rapid and predictable onset of action.

             ·    It must be with minimal CNS side effects to avoid confusion between the disease symptoms and the drug side effects.

             ·    Stepwise reduction of BP is recommended to avoid inadequate organ perfusion. It should be reduced by 1/3 of the total planned reduction during the first 6 hours and the remaining amount over the following 48-72 hours. (Table 1)

             ·    After initial control of BP maintenance therapy can be made with oral drugs.

How to infuse Na nitroprusside?

The contents of the vial is dissolved in 2 ml glucose 5%, then the amount (50 mg) is added to 500 mL glucose 5%. The concentration in this solution is (100 mcg/mL). It is rapidly inactivated by light (photochemical degradation), so bottle and tubing system should be covered with aluminum paper.

The rate of infusion in mL/hour is calculated from the following formula:

Rate (mL/hour) = weight (Kg) ´ dose (mcg/Kg/min) ´ 60 (min/hour) / Conentration (mcg/mL)

2-     Treatment of chronic (non-emergency hypertension): (Table 2)

        ·   The basic rule is to start therapy with ONE oral drug and the starting dose should be low, then it can be gradualy increased every 2-3 days, until the desired therapeutic response is reached.

        ·   If BP remains uncontrolled and combined therapy is needed, the 2 drugs should belong to different groups (different mechanisms of action).

        ·   How to select appropriate drugs to use?

In selecting a drug regimen for long-term use, an understanding of the underlying pathophysiology is helpful to choose the drug that alters the disease pathology as follows:

-         Young patients with essential hypertension who require drug therapy may be treated with the 1^st line drugs initially with a diuretic or a beta-blocking agent or both. Both drug groups may be lipogenic and serum lipids must be followed.

-         Patients with volume-dependent hypertension usually respond adequately to diuretics.

-         Patients with high renin, high cardiac output failure respond best to beta-blockers and if BP is not lowered adequately a Ca-channel blocker may be added and an ACE inhibitor may replace the beta-blocker.

-         ACE-inhibitors are useful not only in patients with high renin hypertension that is secondary to renovascular or renal parenchymal disease but also in patients with high renin essential hypertension.

-         In most cases of neonatal hypertension high angiotensin production is the likely cause which follows partial occlusion of a renal vessel by a thrombus, captopril is an effective agent in most of them but used with careful attention to renal function.

-         In patients with neural crest tumours and high circulating levels of catecholamines, alpha-blocking agents are used and beta-blocking drugs are also needed to control the cardiac rate.

Table (1): Drugs used in hypertensive emergency

Table (2): Common drugs used in control of hypertension in pediatrics.