Moderate or severe hypertension in children

Hypertension is defined as systolic or diastolic systemic arterial blood pressure above normal for age (Fig. 22-88). Moderate or severe arterial hypertension in children is uncommon and usually secondary to a detectable lesion. In adults, most arterial hypertension has no detectable cause and is termed essential or primary. Essential hypertension is common; there are about 60 million people with arterial pressures above 140/90 mm Hg in the United States. Milder forms of hypertension may be common at all ages.

Measurement of blood pressure

The first time a patient is seen, measure blood pressure in at least one arm. If it is high, then measure pressures in the other arm and at least one leg. At subsequent visits, measurement in one arm is adequate as long as all pulses feel equal and the patient is over 2 months old. When pressure is measured in the arm, the patient should be resting and relaxed, in a quiet room, and either sitting or supine. Place the arm at heart level and apply a cuff firmly to the upper arm so that the center of the rubber bag within the cuff is over the brachial artery. The rubber bag must be wide enough to cover two thirds of the length of the upper arm and long enough to cover at least three fourths of the arm circumference. One of the most common causes of apparent hypertension is erroneous measurement from using too small a blood pressure cuff. Feel the brachial or radial pulse and inflate the cuff until the pulse disappears, then deflate the cuff and note the pressure at which the pulse reappears. After about 15 seconds, reinflate the cuff to about 30 mm Hg above the palpatory systolic pressure, place the stethoscope on the brachial artery, and deflate the cuff by 2 to 3 mm Hg per second. The first Korotkoff sounds indicate the systolic pressure. The sounds become louder, then suddenly become muffled, and finally disappear. The point of muffling (fourth phase) may be a better estimate of diastolic pressure than is the point of disappearance (fifth phase), which occasionally gives a false low reading. Repeat the measurements twice; often the third pressure is the lowest because the patient is more relaxed. Record the pulse rate with each measurement because tachycardia may denote anxiety that increases blood pressure. Leg pressures are measured with the patient prone so that the stethoscope can be placed on the popliteal artery. The rubber bag should cover two thirds of the thigh length and at least three fourths of its circumference; thus, a larger cuff is needed for the leg than for the arm.

In infants, blood pressure may be difficult to obtain by this method but can be measured by ultrasound (Doppler) devices.