As people’s standard of living improves, the incidence of hypertension in children tends to increase gradually. Some data confirm that children with blood pressure above the 90th percentile for that age are more likely to develop adult hypertension than children in the 50th percentile by more than 3/4. Children with systolic blood pressure above the norm have an increased chance of developing hypertension and metabolic diseases in adulthood.
Hypertension is the most important risk factor for cardiovascular disease in the Chinese population and is easily overlooked in its early stages due to the lack of obvious clinical symptoms, but studies have shown that children and adolescents with persistently high blood pressure can develop early atherosclerotic lesions. Therefore, the diagnosis and treatment of hypertension should begin in children. The purpose of this article is to review the diagnosis, etiology and treatment of hypertension in children.
1.Diagnostic criteria of hypertension in children
There is no unified standard for the assessment of hypertension in children. It is difficult to develop criteria for hypertension in children by referring to the World Health Organization (WHO) standard method for hypertension in adults, because blood pressure values are distributed continuously in the population, while children are in the growth and development period, and there is no absolute dividing line between normal blood pressure and hypertension, so a threshold can only be artificially developed as a standard for children of various ages. There is no absolute boundary between normal blood pressure and hypertension in children during their growth period, and only an artificial threshold can be established to serve as a standard for blood pressure in children at different ages.
The current international definition of hypertension in children by the National High Blood Pressure Education Program (NHBPEP) Children and Youth Working Group in 2004 is: 3 or more mean systolic and/or diastolic blood pressures greater than or equal to the 95th percentile of blood pressure in children of the same sex, age and height. 95th percentile.
Using the percentile method, children with hypertension were classified into pre-stage, stage I, and stage II according to the following criteria Stage I: blood pressure between the 95th and 99th percentile plus 5 mm Hg; Stage II: blood pressure greater than the 99th percentile plus 5 mm Hg.
White coat hypertension is defined as blood pressure greater than the 95th percentile when measured in a medical facility, such as a clinic or hospital, and less than the 90th percentile when averaged outside of a medical facility. Ambulatory blood pressure monitoring (ABPM) can avoid the effects of emotional stress and other factors on blood pressure measurement, and is often used to determine the diagnosis.
2.Measurement of blood pressure in children
Blood pressure should be routinely measured in children over 3 years of age during medical visits; the preferred method of measuring blood pressure is auscultation; an appropriate cuff is important for accurate measurement of blood pressure in children; and must be repeated several times before a child is determined to have hypertension. blood pressure should be measured at least once during each visit in children over 3 years of age.
Blood pressure should be measured in children younger than 3 years of age when
1. have a previous history of prematurity, low birth mass, or other conditions requiring intensive care in the neonatal period;
2. congenital heart disease (repaired or unrepaired);
3, recurrent urinary tract infections, hematuria or proteinuria;
4. Combination of known renal disease or urinary system malformation;
5.Family history of congenital kidney disease;
6, solid organ transplantation;
7, malignant disease or bone marrow transplantation;
8, Application of drugs that have an effect on blood pressure for treatment;
9, other systemic diseases that accompany hypertension (such as neurofibroma, tuberous sclerosis, etc.) ;
10.Increased intracranial pressure.
The preferred method of blood pressure measurement is by auscultation with a standard clinical sphygmomanometer (mercury column sphygmomanometer): place the bell-type stethoscope chest piece in the middle of the proximal elbow fossa, on the brachial artery pulsation, below the bottom edge of the cuff (2 cm above the elbow fossa). Stimulating drugs or food should be avoided before measurement, and the blood pressure of the right upper extremity should be measured in a sedentary position for 5 min, with the right upper extremity supported and the elbow flush with the heart as far as possible.
The size of the cuff is important for the accurate measurement of blood pressure. The appropriate cuff size is usually chosen according to the size of the upper arm of the child being tested: the width of the cuff filling bladder should be at least 40% of the circumference of the upper arm between the hawk’s beak and the peak of the shoulder, and the length should be 80-100% of the circumference of the upper arm, with a ratio of approximately 1:2 between the width and length of the bladder.
Before a child can be diagnosed with hypertension, elevated blood pressure must be detected at several visits. Blood pressure levels are not stable and usually fluctuate at rest. An accurate description of blood pressure levels is the average of several blood pressure measurements over several weeks and months.
3. Causes of hypertension in children
Hypertension in children, like adults, can be divided into two categories: primary and secondary hypertension. Most hypertension in children, especially in prepubertal children, is often secondary to an underlying condition, with renal parenchymal disease being the most common cause[5] (60% to 70% of cases). As age increases, the proportion of primary hypertension gradually increases, and by adolescence, hypertension is mostly primary (85% to 95% of cases). The main causes of neonatal hypertension are congenital renal parenchymal anomalies, aortic constriction (infantile type), intracranial hemorrhage, hypoxic-ischemic encephalopathy, umbilical artery catheter and renal artery embolism, etc. Etiology of hypertension in children of different ages from 1 to 18 years.
(1) Genetic factors
Hypertension in children shows a strong family tendency. It is thought that this strong genetic predisposition is detectable in infancy. Blood pressure correlations between adoptive parents and their children are significantly lower than those between biological parents and their children. Wolfgan et al. concluded that there was a significant increase in serum CRP concentrations in children with hypertensive parents compared to children without hypertensive parents, suggesting a role for inflammatory factors in the aggregation of familial hypertension.
Shaoqi Rao [8] et al. showed the genetic correlation of familial hypertension, and the expression of GATA64A09 was positively associated with hypertension in a longitudinal study of hypertensive families. Zhao R. B. et al. randomly selected 7963 students aged 8-17 years from seven middle and elementary school in Guiyang city as study subjects and found 411 hypertensive individuals with an incidence of 5. 16 %. Among 2,830 students with positive family history, 166 had hypertension with an incidence of 5. 87%, while those without family history were 5,133 and 245 had hypertension with an incidence of 4. 77% (χ2 = 4. 45, P < 0. 05).
(2) Obesity
Obesity in children and adolescents has become a social concern, especially in relation to hypertension. It has been suggested that the risk of hypertension in obese children is three times higher than in non-obese children . In 1996, an epidemiological survey of 208,523 Han Chinese children aged 0.1-11 years in mainland China found that both systolic and diastolic blood pressure increased with body mass index (BMI), and each unit increase in BMI was associated with a 0.13 kPa increase in systolic and diastolic blood pressure.
(3) Insulin resistance
Insulin resistance is a condition in which the biological effect of a certain amount of insulin produced by the body is lower than the expected level. Hypertension is an important component of the metabolic syndrome, and insulin resistance is the basis of the metabolic syndrome. Some experiments have confirmed that plasma insulin levels are significantly higher in patients with essential hypertension than in controls. It has been suggested that insulin resistance may affect blood pressure changes by increasing sodium retention, exciting the sympathetic nervous system, stimulating vascular smooth muscle cell growth, and increasing blood lipid concentrations.
(4) Pregnancy factor
As early as the 1970s, it was suggested that intrauterine development of the fetus during gestation also has an effect on blood pressure in children. A large number of epidemiological studies have confirmed that blood pressure is negatively correlated with birth weight. The blood pressure of very low birth weight (< 1500g) and normal birth weight (> 2499g) infants was measured at the age of 18 years and found higher systolic and diastolic blood pressures in very low birth weight adolescents. It is thought that this negative correlation may affect the structural resistance of the fetal arterial vasculature, hormone levels and the development of the renal unit. This negative correlation can persist into adulthood as a cause of essential hypertension.
(5) Other factors
Irrational dietary structure, children’s behavior and hygiene habits, impatience, noise, chronic mental stress, sleep deprivation, socio-family economic status, parents’ education level, city of residence, and migration from areas with low prevalence of hypertension to areas with high prevalence of hypertension can all affect hypertension in children.
4.Treatment of hypertension in children
There are no international guidelines for the treatment of hypertension in children.
Treatment recommendations for hypertension in children.
(1) Pre-hypertension: non-pharmacological treatment (weight control counseling if overweight, regular physical activity, and diet control); usually no pharmacological treatment is required unless there are necessary indications such as chronic kidney disease, diabetes, heart failure, or left ventricular hypertrophy.
(2) Hypertension stage I: drug therapy should be started when non-pharmacological treatment is unsatisfactory, such as the presence of clinical symptoms of hypertension, secondary hypertension, hypertensive target organ damage, and combined type 1 or type 2 diabetes mellitus, while non-pharmacological treatment is available.
(3) Hypertension stage II: non-pharmacological treatment is added with pharmacological treatment.
Non-pharmacological treatment
Control of body mass is the most basic treatment for obesity-related hypertension. Regular physical activity and limiting sedentary time may improve the effect of controlling body mass. Dietary modification should be performed in children with prehypertension and hypertension. Self-testing of sedentary time, including watching TV videos and playing computer games, is encouraged to limit sedentary time to less than 2 h per day.
Regular physical activity is beneficial to the cardiovascular system, and regular aerobic physical activity of 30 to 60 min per day of moderate physical activity is recommended. It is believed that regular physical activity and limiting sedentary time may prevent the development of obesity, hypertension and other cardiovascular risk factors. However, competitive physical activity should be limited when stage 2 hypertension is not controlled.
Appropriate dietary modifications include reducing the intake of sugary drinks and high-energy snacks; increasing the intake of fresh fruits, vegetables, fiber, and nonsaturated fatty acids; reducing salt intake; and recommending a regular diet that includes a healthy breakfast. Analysis of randomized studies found that salt intake in infancy can affect blood pressure in adolescence. The recommended daily salt intake is 1.2 g/d for children aged 4 to 8 years, and 1.5 g/d for older children.
In summary, a healthy lifestyle for all children and adolescents includes regular physical activity, a diet rich in fresh fruits and vegetables, fiber, low-fat diet, and limited salt intake.
Medication
Indications for pharmacological treatment.
(1) Hypertension stage II;
(2)Secondary hypertension;
(3) Hypertension with clinical symptoms;
(4) Hypertension with target organ damage;
(5) Combined type 1 or type 2 diabetes mellitus;
(6) Persistent elevation of blood pressure even after non-pharmacological treatment. It is generally believed that drug therapy can be tried when the blood pressure still has no tendency to decrease after six months to one year of non-drug therapy.
Principles of drug treatment:
(1) Children with stage I hypertension should start with a single drug when indicated, while children with stage II hypertension often need a combination of two or more antihypertensive drugs to achieve the goal. All antihypertensive drugs should be started at the lowest recommended dose, and the dose should be increased gradually until the blood pressure is satisfactorily controlled. After the highest recommended dose is reached, but the efficacy is still unsatisfactory or intolerable adverse effects occur, the addition of another type of drug or combination should be considered.
(2) Select drugs that do not affect normal development and cause little damage to important organ functions. Clinically used hypertensive drugs include thiazide diuretics (usually the drug of choice), β-blockers, angiotensin-converting enzyme inhibitors (ACE I), calcium channel antagonists (CCB), angiotensin receptor blockers (ARB) α and β-blockers, and vasodilators.
(3) In order to achieve efficacy and minimize side effects, it is best to use drugs with a long duration of action (1 time/d or 2 times/d for 24 h). Severe symptomatic hypertension should be treated by intravenous infusion of anti-hypertensive drugs.
(4) After the blood pressure is satisfactorily controlled, the dose of antihypertensive drugs can be gradually reduced until it is stopped, but should not be stopped suddenly.
(5) The dose of antihypertensive drugs should not be adjusted too frequently (the frequency should not be shorter than 1 time in 2-3 days).
(6) Regular monitoring of blood pressure and evaluation of treatment effects are required during the treatment of hypertension.
The goal of pharmacological treatment: For children with essential hypertension without comorbidities and without target organ damage, the goal of blood pressure control is to reduce blood pressure to below the 95th percentile for children of the same sex, age, and height. However, for children with renal disease, diabetes mellitus, or hypertensive target organ damage, the blood pressure control goal is to reduce blood pressure to below the 90th percentile for children of the same sex, age, and height.
Severe symptomatic hypertension at blood pressure levels above the 99th percentile can occur in children, often with kidney disease, and requires urgent treatment. Hypertensive crisis in children is often accompanied by symptoms of hypertensive encephalopathy, which can lead to convulsions. Hypertensive crisis should be treated with emergency intravenous antihypertensive medication, with the goal of lowering blood pressure by about 25% within 8 hours of presentation and to normal over the next 26 to 48 hours.
Other treatments
For hypertension caused by renal embryoma, adrenal tumor, pheochromocytoma, intracranial tumor, neuroblastoma, renal vascular malformation, and aortic stenosis, surgical treatment is possible. In recent years, due to the increasing maturity of interventional techniques, percutaneous balloon catheter dilation or endovascular stenting has also achieved good results in the treatment of hypertension caused by renal artery stenosis and aortic constriction.