Childhood Hypertension

Hypertension occurs in 1-3% of children. Hypertension may occur at any phase of childhood, in newborns up to adolescence. Hypertension in children is statistically based on the normal distribution of systolic and diastolic pressures of the general population of children of the same age, gender and height.

Childhood hypertension is defined as systolic or diastolic pressures greater than or equal to the 95th percentile for age, height and gender. Normal blood pressure is defined as systolic and diastolic blood pressure that is less than the 90th percentile for age, gender and height.

Childhood hypertension is further classified into:

• High normal blood pressure- between the 90th and 95th percentile.
• Significant hypertension- blood pressure between the 95th and 99th percentile.
• Severe hypertension- blood pressure greater than the 99th percentile.

It is recommended that blood pressure screening for children should begin at 3 years of age.

A mercury column or aneroid manometer with an appropriate sized cuff should be used to measure the blood pressure. However automated devices for measuring blood pressure may be recommended for newborns and children in whom blood pressures need to be taken frequently.

A health care professional should ideally have a table(s) showing the standard distribution of blood pressure levels for the age, weight, height and gender of children. The child's blood pressure obtained is interpreted by comparing with the blood pressure table.

CAUSES

Hypertension in children can either be essential (primary) hypertension or secondary hypertension. Essential hypertension accounts for 10-20% of cases of hypertension in children less than 10 years old and 35% of cases of hypertension in adolescents. Secondary hypertension, on the other hand, accounts for up to 90% of cases of hypertension in children less than 10 years old and 65% of cases in adolescents.

Hypertension is uncommon in healthy newborns and secondary causes account for the majority of cases of hypertension in newborns. The commonly identified causes of hypertension in newborns include:

• Kidney disease associated with blockage (renal artery thrombosis), stenosis or constriction of the renal artery (renal artery stenosis) in one or both kidneys. The renal arteries supply the Kidney with blood pumped from the heart. An interruption in the blood supply to the kidney interferes with its excretory function. Inability to excrete salt and water will directly lead to an elevated blood pressure.
• Coarctation of the aorta.
• Kidney malformations.
• Bronchopulmonary dysplasia- this is a chronic lung condition that is most common in children born prematurely, with low birth weights and who recieved prolonged mechanical ventilation to treat respiratory distress syndrome.

The most common causes of hypertension in infants and children up to 10 years old include:

• Renal artery stenosis.
• Renal parenchymal disease such as acute and chronic glomerulonephritis.
• Coarctation of the aorta.
• Kidney scarring following repeated kidney infections.

The secondary causes of hypertension in the adolescent years include:

• Illicit substance use- examples of such drugs are nicotine, cocaine, amphetamine related compounds and cannabis.
• Other substances associated with high blood pressure include use of oral contraceptives, excessive alcohol intake, use of anabolic steroids and use of appetite suppressants.

Essential hypertension, however, accounts for the majority of cases of hypertension occurring in adolescents. Essential hypertension in children is frequently associated with obesity. Obese children and adolescents may benefit from a reduction in weight as it has been shown to be associated with a reduction in blood pressure.

SYMPTOMS

Children with essential hypertension or mildly elevated blood pressure due to secondary causes usually have no symptoms. Infants with hypertension may have symptoms such as convulsions, poor feeding, irritability and difficulty in breathing. Severe hypertension may be associated with convulsions, bleeding from the nose (epistaxis), headaches, dizziness, and nausea.

TREATMENT

The goal of treatment of hypertension in children is to reduce the blood pressure to less than the 90th percentile. The treatment approaches employed in children are similar to those used to control blood pressures in adults. Weight reduction, dietary modifications (such as reduced intake of salt and saturated fat), and aerobic exercise may facilitate blood pressure control. The use of prescription medication is indicated for children with significant hypertension, in whom lifestyle modifications have failed, or children with severe hypertension, or children with presence of end organ injury manifesting as cardiac disease.

Most of the medication used in adults can be used in children. However, data on the efficacy of these medications for the pediatric population are limited. The type of medication and the dosage of the drug to be used will depend largely on the experience of the healthcare professional. The choice of antihypertensive medication must be individualized and depends on the child's age, the cause of the hypertension, the degree of blood pressure elevation, side effects of the drug used and interactions with other medication. In most cases, treatment is begun using a single agent. The dose of the drug used may be increased gradually until the blood pressure is effectively controlled. A second agent may be used if the maximum dose of the first agent failed to effectively control the blood pressure.