Childhood hypertension : Practical approaches towards diagnosis and management

Cardiovascular disease is now the leading cause of premature mortality among adults and hypertension confers the highest attributable risk to these deaths. Since blood pressure (BP) tends to track along the same percentiles throughout life, it is accepted that children with elevated BP are more likely to become hypertensive adults. Early identification of childhood hypertension and early intervention are crucial to reduce the cardiovascular morbidity and mortality during adulthood. Even though the importance of BP measurement in children was recognized and incorporated into the routine paediatric examination more than 2 decades ago, there are still many doubts among physcians regarding assessment and evaluation of hypertension in children. There has been significant new knowledge gained about many aspects of childhood hypertension over the past decade. This article aims to discuss the fundamentals of BP measurement and some practical approaches towards the diagnosis and management of hypertension in children based on evidence from the most updated literature.


White-coat hypertension
The patient has BP levels that are ≥95th percentile when measured in a hospital or clinic but are <90th percentile outside of a clinical setting.
# If systolic and diastolic categories are different, categorize by the higher value.* This typically happens at 12 years old for SBP and at 16 years old for DBP.
BP records <90 th percentile for gender, age and height are considered as normal.If the BP is ≥90 th percentile for gender, age and height it should be repeated twice and the average taken.Children in the pre hypertensive stage have a heightened risk for developing hypertension and those children with stage 2 hypertension have a higher risk of acute and chronic organ damage.________________________________________ 1

Consultant Paediatric Nephrologist, Lady Ridgeway Hospital for Children, Colombo
Blood pressure measurement as a routine clinical procedure 2 • Children ≥3 years old who are seen in medical care settings should have their BP measured at least once during every health care episode.
• Children <3years old should have their BP measured in following special circumstances:

Method for BP measurement in children
In BP measurement, mere obtaining of a value is fruitless unless an accurate method is followed using proper devices.It is of paramount importance to use a cuff appropriate to the size of the child's upper right arm and the dimensions of the inflatable bladder underneath the cuff are very crucial.By convention, an appropriate cuff size is a cuff with a bladder width that is at least 40% of the arm circumference at a point midway between the olecranon and the acromion 3,4,5 .For such a cuff to be optimal for an arm, the cuff bladder length should cover 80% to 100% of the circumference of the arm 5 .Such a requirement demands that the bladder width-to-length ratio be at least 1:2.All the commercially available cuffs do not meet these standards.Therefore, the working group has recommended to adopt the dimensions given in table 2 when selecting an appropriate cuff.If a cuff is too small the next largest one needs to be used 2 .Mercury sphygmomanometer is the standard device for BP measurement.Aneroid manometers are also quite accurate when calibrated on a biannual basis 2 .The popular oscillometric devices are convenient but may not be accurate, necessitating regular validation as per standard protocols 2 .They also tend to give higher values than auscultatory methods.Since the standard BP tables are based on BP values taken by the latter method, it is advised to confirm higher oscillometric values by auscultation 2 .Correct technique of measuring BP using auscultation is given in figures 1 and 2.

BP tables
The most recently updated BP tables of children and adolescents are based on gender, age and height and they include the 50 th , 90 th , 95 th , and 99 th BP percentiles for several differnt height percentiles.This approach avoids misclassifying children who are very tall or very short.Normative BP values for infants under 1 year of age are according to the Second Task Force report 6 (see Figures 3-4).Defining normative blood pressure data in newborn infants is a complex task.Extremely useful data in this regard has been published by Zubrow et al 7 (see figure 5A, B & C).I have not included the normative BP tables for children >1 year since I assume our readers are well familiar with them.

What is ambulatory blood pressure monitoring 8 (ABPM)?
ABPM is a non-invasive method of monitoring BP over a fixed time interval, usually 24 hours.It involves a BP cuff attached to a small portable monitor.BP recordings are automatically obtained at prefixed time intervals and recorded by the monitor.Hypertension can be determined based on several indices calculated using these data.ABPM is especially helpful in the evaluation of whitecoat hypertension, risk for hypertensive organ injury, apparent drug resistance, hypotensive symptoms with antihypertensive drugs and BP patterns in special conditions such as episodic hypertension, chronic kidney disease (CKD), diabetes mellitus (DM) and autonomic dysfunction.

Common causes of of secondary hypertension in children
Classification by aetiology

Hypertension of the newborn
RVD is the commonest cause of hypetension in the newborn period.Several predisposing factors for renovascuar accidents in the newborn are identified and a clear association between use of umbilical arterial catheters and development of arterial thrombi has been demonstrated 11 .The next largest group comprises of RPD mainly cystic kidney diseases and other structural anomalies of the kidneys 11 .Invasive laboratory investigstions can be largely avoided in the majority of these neonates with a careful history and examination.

Basic diagnostic investigations
Basic investigations can be catergorized into 3 groups 10

Table 3 : Common causes of secondary hypertension by age
Note: This table covers only the common causes for each age group.

Practical approaches for diagnosis 2,9,10 Clues for diagnosis of common aetiologies
The goal is to reduce BP to a safe level to limit further end-organ damage.4. Initial rapid decrease may be harmful due to disrupted cerebral auto-regulation 5. Frequent blood pressure monitoring 6. Neuro-observations and pupillary reactions 7. Aim to reduce blood pressure slowly Patient needs at least 2 large bore iv cannulae Ensure that an intravenous fluid bolus can be given if BP drops acutely Clinicians caring for children & adolescents should familiarize themselves with current practices of managemnt of hypertension in this age group and incorporate them into their clinical decisionmaking.Early and accurate diagnosis, appropriate referral and timely intervention and follow up of these patients will reduce acute morbidity as well as future burden of adult cardiovascular morbidites and mortalities related to hypertension.