Measuring blood pressure in children

Abstract

In theory should be routine, but in practice is rare

Although the theory behind measuring blood pressure in children is well known, in practice it is rarely done. One review stated that “measurement of blood pressure is now firmly established as an important component of the routine paediatric physical examination,”¹ but studies in practice prove otherwise. In the United States and Australia, between 5.3% and 66% of children attending emergency departments had their blood pressure measured,^{2 3 4} and in the United Kingdom this figure was about 9%.⁵ It is almost automatic to measure blood pressure in adults in the emergency department, so why are we so bad at doing this in children?

Firstly, measuring blood pressure in children is more difficult than in adults—for example, readings are likely to be falsely high in crying toddlers, normal ranges for blood pressure are often not displayed on the clinic wall, and an appropriately sized cuff may not be available in the triage room. Secondly, if a child is in shock, capillary refill time is easier and quicker to measure and, hopefully, acutely sick children would be identified before they become hypotensive because this is a preterminal sign.⁶ Thirdly, no clear definition exists on what constitutes abnormal blood pressure in children.⁷ Finally, clear guidance as to when blood pressure should be taken in triage is lacking.

Paediatric resuscitation guidelines make it clear that it is important to measure blood pressure when assessing a sick child’s circulatory and neurological status: “Hypotension is a late and pre-terminal sign of circulatory failure. Once a child’s blood pressure has fallen cardiac arrest is imminent. Hypertension can be the cause or result of coma and raised intracranial pressure.”⁸

The epidemic of childhood obesity worldwide—affecting mainly poorer socioeconomic groups in developed countries and higher socioeconomic groups in developing countries—makes it even more important to measure blood pressure in children. Rates of childhood obesity have increased 2.0-2.8-fold over 10 years in the UK and 3.9-fold over 18 years in Egypt.⁹ In Australia, 23% of children are overweight and 6% are obese.¹⁰

Childhood hypertension is no longer limited to renal, metabolic, and other rare secondary causes but seems to track the growing rates of obesity in children, their reduced physical activity, and the development of maturity onset diabetes in this group. Jackson and colleagues produced new blood pressure centiles based on 23 000 UK children and found that high blood pressure is linked more to weight than height, after adjusting for age.⁷ They also estimated the prevalence of high blood pressure in UK children to be 2.3%, and borderline “high normal” blood pressure to be 6.9% (they propose a new definition of hypertension for UK children as a blood pressure above the 98th centile, replacing the former measurement greater than the 95th centile, with a new definition of “high normal” lying between the 91st and 98th centiles).⁷ Hypertension in childhood may predict heart disease in later life,¹¹ just as raised body mass index predicts coronary heart disease in adulthood.¹²

Definitions of childhood obesity vary, but it is a multisystem disorder linked to raised body mass index that has multiple physical and psychological consequences for an affected child.⁹

Measuring blood pressure is a cheap, relatively quick, and non-invasive way to screen for hypertension in children. Taking into account the Wilson criteria (the condition should be an important health problem; it should be detectable early on, so that primary prevention can be cost effective; and the pathophysiology and epidemiology should be well understood), it could be argued that all children with a raised body mass index should be screened by both a paediatrician and a general practitioner. Detecting hypertension at an early stage might improve the benefits of interventions like exercise and an improved diet.

Research is needed to establish more accurately what actually constitutes childhood hypertension and how best this might be detected given the demands made on already stretched health services. For example, a pilot screening programme in clinically obese children would be useful, with further research to investigate whether interventions to tackle childhood obesity actually reduce blood pressure and overall cardiovascular risk.

In the meantime, healthcare workers should be reminded of how simple it is to measure blood pressure in children. The cuff must cover at least two thirds of the right upper arm, between the olecranon and the acromion, with blood pressure readings from properly calibrated equipment measured against established centiles for age, sex, height, and weight. Measurement should be repeated at least twice when an abnormally high result is obtained.

Because rates of hypertension look set to rise alongside those of obesity, we should examine services to ensure that optimal systems exist for measuring and recording blood pressure in children and tracking abnormal results. A similar system to that in place for adultsin primary care and hospital clinics could be applied to children with raised body mass index, and frontline healthcare staff need to be educated about the importance of measuring children’s blood pressure in the acute setting. If we put as much effort into detecting and tracking abnormal blood pressure as we do for the follow-up of urinary tract infections in children, which can include ultrasound and dimercaptosuccinic acid (DMSA) scans, we might make a greater impact on the consequences of hypertension in later life and improve our care of acutely unwell children.