Paediatric Hypertension (includes downloadable software) E-Book

Chiara Giovannozzi

• Herausgeber: SEEd Edizioni Scientifiche
• Kategorie: Fachliteratur
• Sprache: Englisch

Veröffentlichungsjahr: 2010

Beschreibung

The first objective of this book is to remind all pediatricians that hypertension in children does exist, and that it can be easily diagnosed and managed. The covered topics range from the regulation of blood pressure and its assessment in children to day-to-day management. The attached calculator provides a hypertension assessment software: entering data about sex, height, systolic and diastolic pressure, the program indicates the presence and severity of hypertension. On the basis of international guidelines, it further suggests the opportunity of a treatment and helps to choose the appropriate among behavioral or pharmacological alternatives.

Leseprobe

Paediatric hypertension

Chiara Giovannozzi

Colophon

© SEEd srl

Piazza Carlo Emanuele II, 19 – 10123 Torino – Italy Tel. [phone] – Fax [email protected]

Title of original Italian edition Ipertensione in pediatria. By Chiara Giovannozzi

First edition September 2010 ISBN 978-88-8968-852-6

Although the information about medication given in this book has been carefully checked, the author and publisher accept no liability for the accuracy of this information. In every individual case the user must check such information by consulting the relevant literature.

This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the Italian Copyright Law in its current version, and permission for use must always be obtained from SEEd Medical Publishers Srl. Violations are liable to prosecution under the Italian Copyright Law.

1 Introduction

For a lot of paediatricians hypertension is a field yet unknown. We rarely measure the blood pressure of our little patients, particularly if they have a normal body weight and they haven’t any symptoms. But the literature says clearly that this pathology is not as rare as it’s usually thought to be [1].

In recent years much progress has been made in paediatric hypertension diagnosis, management, and therapy. Taken together, these developments give us hope that hypertension damage, both short-term (rarer) and long-term (more important for number and complexity) can finally be prevented.

In addition, paying attention to hypertension control allows us to reflect on the effects of lifestyle on health status: few pathologies, such as this one, are so tightly bound to food, sport, work practices, and sleep-wake rhythm. Checking these aspects with scrupulousness also allows us to prevent and often to treat not only the hypertension of children, but also a lot of other pathologies of our little patients—in particular those peculiar to the age in which we live and to an affluent society, primarily the obesity and the overweight that, according to recent statistics, affect almost one third of Italian children under fourteen years of age (and the situation is similar in most of the western countries).

The aim of this book is first of all to remind paediatricians that hypertension exists also in children; then to provide them with a tool for diagnosis and therapy of hypertension in their little patients. In fact, as can be easily imagined, hypertension management in paediatrics is different from hypertension management of the adult or of the elderly: first because the causes are different, at least concerning the frequency; then because of the different response capacities of the organisms to hypertensive damage, the different life expectancies, and the concept of “quality of life.”

The book is complemented by a calculator (available at http://download.edizioniseed.it using the code 28NL96BE) that allows the paediatrician, starting with the age, sex and height of the patient, to determine the presence and the degree of hypertension in the paediatric age group, evaluating the subsequent necessity to start behavioural and pharmacological therapy.

I hope that through this text my colleagues can, as happened to me, discover the world of hypertension in children and suspect the presence of hypertension if there are suggestive symptoms; but also, in the absence of symptomatology, learn how to discover the disease and treat it, and avoid the important damage that can slowly develop in the future adults we are helping to grow.

The Author

Chiara Giovannozzi

2 Definitions

In the paediatric age there aren’t, as there are for adults, universal threshold limiting values for arterial pressure: vice versa, there are tables with blood pressure percentiles based on height percentiles, age, and sex (see Paragraph 3.4).

The definitions here reported derive from the reference works “The Fourth Report on Diagnosis, Evaluation, and Treatment of High Blood Pressure in Children and Adolescents” [2] and “The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC7)” [3].

Hypertension in children is defined as the mean of systolic or diastolic blood pressure above the 95th percentile for age, sex, and height on almost three different controls.

Children and adolescents with blood pressure between the 90th and the 95th percentile suffer from blood pressure at the upper normal limit (“high normal”), defined as prehypertension from JNC7: these subjects are at high risk of developing hypertension in the future, and therefore they must be monitored more carefully and more frequently. In particular, it’s important to propose lifestyle modifications to them in order to prevent the onset of hypertension.

There is also white coat hypertension, which refers to the condition of those patients who have pressure levels above the 95th percentile when measured in the medical ambulatory, or when measured at home, between the 90th and the 95th percentile.

3 Measuring Blood Pressure in Children

3.1 For Whom and When?

Conditions in which to recommend the measurement of arterial pressure to children younger than three

A personal history of prematurity, very low weight at birth, or complications in the neonatal period needing intensive careCongenital cardiopathies (operated on or not)Recurrent infections in the urinary system, proteinuria, or haematuriaNephropathy or uropathyFamiliar anamnesis of congenital nephropathyTumoursBone marrow transplantSolid organ transplantTreatment with blood pressure-elevating drugsIntracranial hypertensionOther pathologies known to be associated with hypertension (neurofibromatosis, tuberous sclerosis, etc.)

The incidence of arterial hypertension in childhood varies, according to statistics, between 4% and 6%. In children, so-called secondary hypertension, due for example to nephrovascular or endocrine causes, or to coarctation of the aorta, represents between 50% and 85% of all hypertension, while primary hypertension covers less than half of the pathology.

Often, in children, hypertension presents no symptoms, and so it’s important to verify its presence in an active way. Blood pressure measurement is recommended for all children older than three every time they are visited in a paediatric ambulatory [4].

On the contrary, for children younger than three years of age, blood pressure should be measured if the subject belongs to particular high risk categories, such as for example premature infants or very low weight infants, children with cardiac or renal problems and children assuming blood pressure elevating drugs.

3.2 How

Blood pressure measurement has to be performed with the auscultatory method, because blood pressure percentile tables for children, which represent the reference standard, are based on data obtained by measurements performed with this method.

There are instruments that measure blood pressure in a different way, for instance with an oscillometric method; these instruments are often reliable and able to prevent human error, but they furnish data partially different from those obtained with the auscultatory method, and so are not comparable to those of the percentile tables. Oscillometric instruments measure the mean arterial blood pressure and then they calculate the maximum and the minimum pressures using algorithms varying from brand to brand and from instrument to instrument; this is also why it is difficult to compare pressure values registered with this method to those obtained with auscultation. Furthermore, oscillometric instruments, to be precise, must be regularly validated; but the validation process is complex and difficult to perform. Nevertheless, the utilization of automatic instruments is preferable in particular circumstances: such as with newborn and unweaned babies, where auscultation can be difficult; and with patients in intensive care units, for whom it’s necessary to measure blood pressure several times during the day. If the pressure values obtained with oscillometric measurements are repeatedly high, it may be necessary for the diagnosis to have a control measurement using the auscultatory method.

The measurement should be performed with a standard sphygmomanometer, positioning the stethoscope at brachial pulse level, in medial position and proximal to the cubital fossa, about 2 cm above it, so that the stethoscope is under the sphygmomanometer cuff. To increase the sensitivity in perceiving Korotkoff sounds, it’s possible to use a stethoscope bell. The standard instrument for arterial pressure measurement is the mercury sphygmomanometer; nevertheless, since mercury is toxic to the environment, often these instruments are no longer used. Aneroid manometers are valid alternatives, particularly if they are calibrated at least every six months.

In children the choice of an adequate cuff measure of the sphygmomanometer is particularly important. Sometimes, especially in the youngest children, the adequate cuff choice can determine differences in the right position of the stethoscope compared to those cited above. Nevertheless, it has been shown that a little variation in the displacement of the stethoscope doesn’t invalidate a correct arterial pressure measurement, even if it was in contact with the sphygmomanometer cuff. Conventionally, a cuff with an appropriate measure is one with an insufflable part of a height at least 40% of the arm circumference of the proband, measured at half of the straight line that joins the olecran to the acromion; and a width between 80% and 100% of the circumference itself. This requires that the ratio between the height and the width of the insufflable part of the cuff be at least 1:2.

The working groups on arterial pressure have even defined the sizes of the cuffs per age group: for instance, the right cuff for a newborn baby must measure 4 x 8 cm, assuming that the arm circumference of the baby is at most 10 cm. Likewise, the cuff for unweaned babies must measure 6 x 12 cm, the one for children 9 x 18 cm, and the one for adolescents and young adults 10 x 24 cm. Furthermore, it’s important to be supplied with cuffs for adults, of small and large size, for pressure evaluation in older adolescents [5]. The use of a cuff too small leads to an overestimation of arterial pressure, while one too big leads to an underestimation. If a right size cuff is not available, a bigger size is better than a smaller one, because in this way the error is lower.

Pressure measurement must be performed when the child is calm and has been sitting quietly for almost five minutes, without having taken excitant food or stimulant drugs in the previous hours. To perform the measurement, the child must sit in a comfortable position with its back supported, the feet must be in contact with the ground, and the right arm must lie so that the cubital fossa is at heart level. In fact, it’s preferable if the measurement is performed on the right arm, both because this value is comparable with the percentile tables, and because there’s a distant possibility of detecting in the left arm a falsely reduced value in case of coarctation of the aorta.

Maximum arterial pressure value is determined by the first Korotkoff sound (K1), the minimum by the fifth Korotkoff  sound (K5) or by the disappearance of the sounds themselves. Nevertheless, there are some children where Korotkoff sounds are audible until the sphygmomanometer indicates 0; in these subjects it’s suitable first of all to check the value again using less pressure on the stethoscope bell; only if in this way too the fifth Korotkoff sound persists very long, is it possible to consider the fourth sound (K4) as the minimum pressure indicator. If an increased pressure is detected, the value must be confirmed by repeated measurements to diagnose a child as hypertensive. In fact, increased values often decrease to the normal range in the following measurements, because the child gets used to the visit and is no longer anxious and worried about the measurement.

3.3 Pressure Doppler

Worn by the patient, a pressure doppler is an instrument that detects pressure values during the desired period of time, usually for 24 hours. Based on frequent measurements and registration of the values of the arterial pressure obtained, it calculates the mean arterial pressure, hypertension grade, and how long over time the pressure values exceed the desired ones. It’s also a useful tool to evaluate both the therapeutic efficacy of a hypertensive drug, and the risk of developing organ damage. Moreover, and this aspect shouldn’t be underestimated, the pressure doppler measurement avoids white coat hypertension, and can help in not judging the most emotional children to be pathological.

3.4 Percentile Tables of Arterial Pressure for Children and Adolescents

As previously cited, there are specific percentile tables for diastolic and systolic pressure evaluation in children and in adolescents. These tables are created using a reference population drawn from various studies and consisting of children and young adults from the United States, in this proportion: 29% Black Americans, 10% Hispanics, and 54% White Americans [2]. Obviously, the chosen population is not representative of Italian or European children, but the tables are considered reliable for our population all the same.

Pressure values are indicated in percentiles for sex, age, and the height of the proband. The tables allow evaluating the blood pressure of children starting from one year of age. There are also standards for arterial pressure in children under one year of age, but they are not reported in this book, because they are related to a very specialised subject. The height percentiles are drawn from CDC (Centers for Disease Control and Prevention) tables, that are reported in the appendix of this book () [6].see Paragraph 8.1

In the pressure tables the following percentiles are indicated:

the 50th percentile, which allows the physician to have an idea of the mean pressure value for that age, height, and sex; andthe 90th, the 95th, and the 99th percentile, which permit the diagnosis of the grade and the severity of the hypertension. In fact, the hypertension level indicates which measures to adopt for a specific patient.

To use the percentile tables, it’s necessary to search for the child’s age in the left part of the table and to follow the horizontal line upwards to the height percentile corresponding to the subject; at that point it’s possible to slide vertically to the pressure values related to the 50th, 90th, 95th, and 99th percentiles.

If a child presents a pressure value above the 90thpercentile, the pressure must be measured again, during the same visit, and must be considered the average of systolic and diastolic pressures. If a child has a pressure value above the 95th percentile, the actions to do vary according to the hypertension grade:

if it is of first grade (between the 95th and the 99th percentile + 5 mmHg), the pressure measurement must be repeated on at least two subsequent occasions; andif it is of second grade (above the 99th percentile + 5 mmHg), the patient must be immediately evaluated for the presence of possible hypertension symptoms or organ damage, and, if these are found, a hypertensive treatment must be undertaken as soon as possible.

In the adolescent, if the pressure values are above 120/80 mmHg, the patient is considered affected by prehypertension, even if the values are below the 90th percentile. The value of 120 mmHg for the systolic pressure is generally reached at about 12 years of age, and 80 mmHg for the diastolic pressure around 16 years of age.

Symptomatic hypertensionSecondary hypertensionDamage of one or more target organs of hypertensionType 1 or type 2 diabetesPersistent hypertension in spite of nonpharmacological therapies

Table I. Indications for antihypertensive therapy in children.

If children are included in some particular categories, for example, diabetics or people with secondary hypertension, they must be treated as if their pressure values belong to the upper risk category. Table I identifies these patients, who must be followed particularly carefully and for whom a pharmacological therapy must be proposed as soon as possible. Table II resumes the classification of hypertension in children and adolescents, with the related control measures and therapy.

The clinical decision regarding which patients must be monitored more carefully and treated more aggressively is of crucial importance. The difference between the 95th and the 99th percentile, especially if obtained after repeated measurements, isn’t wide enough (only 7-10 mmHg) to set a pressure percentile on the proband. So hypertension of moderate grade pertains until values 5 mmHg above the 99th percentile, and only at superior values can a patient be defined as severe hypertensive (in this case a speedier and more aggressive intervention is necessary).

Pressure percentile

Measurement frequency

Behavioural therapy

Pharmacological therapy

Normal

< 90th

At every clinical control

Diet, sleep, physical activity

–

Prehypertension

≥ 90th and < 95th or > 120/80 mmHg

Every 6 months

If overweight: weight control

None in absence of chronic nephropathy, diabetes mellitus, cardiac decompensation, left ventricle hypertrophy

First grade hypertension

≥ 95th and < 99th

+ 5 mmHg

Check again after 1-2 weeks or earlier if symptomatic. If pressure results high on 2 other occasions, check carefully after a month

If overweight: weight control. Physical activity and diet

Therapy if risk conditions (symptomatic hypertension, secondary hypertension, damage at one or more target organs of hypertension, type 1 or type 2 diabetes, persistent hypertension in spite of nonpharmacological therapies, chronic nephropathy, cardiac decompensation, left ventricle hypertrophy)

Second grade hypertension

> 99th + 5 mmHg

Evaluate or send to a specialised centre within a week or immediately if patient is symptomatic

If overweight: weight control. Physical activity and diet

Start the therapy

Table II. Classification of hypertension in children and adolescents. Frequency of measurements and therapeutic measures.

After having been confirmed by repeated measurements, a determination of first grade hypertension allows time for a more careful evaluation before the beginning of the treatment, unless the patient is symptomatic. Patients with second grade hypertension need a speedier evaluation and subsequent pharmacological therapy. Symptomatic patients with second grade hypertension need immediate treatment and an evaluation as soon as possible by an expert in hypertension in children.

4 Primary and Secondary Hypertension in Children

4.1 Primary Hypertension

A child with high blood pressure is at a very high risk to become a hypertensive adult. Discovering and preventing hypertension in children, therefore, means greatly reducing the incidence of cardiovascular disease in adulthood.

The paediatrician is able to identify easily subjects of paediatric age with essential hypertension; it’s sufficient to think about it. Primary hypertension in children is generally of first grade, moderate, and often associated with a family history positive for hypertension or cardiovascular disease. Frequently children with high blood pressure are overweight. In fact, it has been shown that the prevalence of hypertension increases according to body mass index (BMI) and that 30% of children with BMI above the 95th percentile are overweight [7].

This datum, associated with the increase of the prevalence of overweight and obesity in children, indicates that one will see more and more children with prehypertension and overt hypertension. Overweight children frequently suffer a certain degree of insulin resistance; in fact, the elevated blood pressure and the overweight are, along with insulin resistance, characteristic of plurimetabolic syndrome, which represents in turn a risk factor for the development of cardiovascular disease and type 2 diabetes.

The plurimetabolic syndrome is marked by other anomalies that are risk factors for cardiovascular diseases, such as hypertriglyceridaemia, HDL cholesterol decrease, truncal or android type obesity, and hyperinsulinaemia. All these alterations are significantly more frequent among children with elevated pressure than among normotensive children [8]. Obviously the children who, in addition to high pressure, present other features of plurimetabolic syndrome have a much higher risk of developing cardiovascular disease than those with hypertension alone and no other risk factor.

These reflections lead to the necessity to examine hypertensive children thoroughly, to investigate their family history, to visit them carefully, to weigh them, and to perform all the laboratory assessments necessary for the evaluation of their metabolic state. The checking of an elevated fasting insulin level isn’t necessarily an insulin resistance index; it is frequently associated with obesity, independently from the presence of other alterations.

To identify further risk factors, it’s necessary to evaluate the fasting plasma lipid profile and baseline glycaemia in all overweight children with an arterial pressure value above the 90th percentile. If a strong family history of type 2 diabetes is present, it should be useful to obtain glycated haemoglobin values and to subject the child to an oral glucose tolerance test (OGTT). One can’t be satisfied with normal values in a unique control; the risk factors for cardiovascular disease are to be considered periodically, because the metabolic state of the subjects can change over time.

On the other hand, there are no data on the usefulness of checking other factors, such as uric acid or homocystein level, and the necessity for their measurement must be evaluated based on family history. In addition, sleep problems, in particular sleep apnoeas, are associated with hypertension, with coronary pathologies, with cardiac insufficiency, and with infarction in adulthood [9]. Approximately 15% of children snore during sleep and 3% of children present respiration problems when asleep. This is why it’s important to investigate how respiration occurs during slee [...]