With the release of a new report, doctors can more accurately assess blood pressure levels in all children, regardless of differences in growth rates. Updated guidelines issued today by the National High Blood Pressure Education Program, which is coordinated by the National Heart, Lung, and Blood Institute, include height percentiles in blood pressure tables for children up to the age of 17, helping physicians correctly diagnose children with high blood pressure.
In addition to the revised tables, the guidelines also reflect the latest information on the management and prevention of hypertension in children. The new report appears in the October issue of the journal Pediatrics.
Body size is the most important determinant of blood pressure in youth. Since children grow at varying rates, adjustments are required when interpreting blood pressure percentiles for individuals. Blood pressure levels in children at extremes of normal growth can vary from the age/sex norms and so might have been misclassified under previous standards. With the new tables, very tall children who will naturally have higher blood pressure levels are less likely to be misdiagnosed as hypertensive, and very short children with high blood pressure will not be overlooked.
Accurate assessment of blood pressure levels in children is important not only because hypertension can be a symptom of underlying disease, such as kidney dysfunction, but also because elevated blood pressure in children often correlates with hypertension in early adulthood. With early identification of individuals at risk, hypertension may be prevented.
"Accurate blood pressure screening as part of routine childhood exams is essential to both the current and future health of our nation's youth," stated Claude Lenfant, M.D., Director of the National Heart, Lung, and Blood Institute. "The National High Blood Pressure Education Program's working group has delivered an excellent report which provides physicians with the most current guidelines for evaluating blood pressure in children and adolescents," he said.
Blood pressure measurement is further standardized in this report with the establishment of the fifth Kortokoff (K5) sound as the definition of diastolic blood pressure in children as well as adolescents and adults. (Kortokoff sounds are the tapping noise made by the pulse when blood pressure is being measured. The fifth phase of the sounds, K5, is characterized by the disappearance of the sound as the blood pressure cuff relaxes.) "Enough data are now available to support K5 as a consistent measure to define normal and elevated diastolic blood pressure throughout life," noted Bonita Falkner, M.D., Professor of Pediatrics and Medicine at Allegheny University in Pennsylvania.
Dr. Falkner chaired the working group of seven experts in pediatric hypertension who authored the report. Additional review was provided by experts in pediatrics, cardiology and hypertension. The National High Blood Pressure Education Programs's Coordinating Committee, whose members represent 44 voluntary and professional organizations, reviewed all drafts and approved the final report.
Following the guidelines for appropriate size and positioning of the blood pressure cuff for children, health care providers should measure blood pressure at least twice on each occasion after three to five minutes of rest. The two readings are averaged to produce the blood pressure measurement. The child's measured systolic and diastolic blood pressure is then compared to the numbers in the table for age, sex and height percentile.
The actual definitions of blood pressure levels in children have not been altered from the Report of the Second Task Force on Blood Pressure Control in Children issued in 1987. A child's blood pressure is normal if the numbers are below the 90th percentile. If either the average systolic or diastolic blood pressure is greater than or equal to the 90th percentile but less than the 95th, the measurement is high normal and may indicate treatment. If either the systolic or diastolic blood pressure is at or above the 95th percentile, the child may be hypertensive and repeated measurements are required to confirm the diagnosis.
Most children with markedly but not severely elevated blood pressure are overweight and have a family history of hypertension. The report recommends that these children, as well as those with high normal blood pressure, be treated with non-pharmacologic therapy, including weight reduction and increased physical activity. Considering the excess burden of illness and death due to hypertension among African-Americans, the report urges careful monitoring of blood pressure and encouragement of healthy diet, exercise, and weight control behaviors in these children.
Children with severe hypertension may be treated with drugs to reduce blood pressure levels to below the 95th percentile. Children with kidney disease or diabetes may benefit from further reductions in blood pressure. Guidelines for the use of antihypertensive medication in children presented in the 1987 report continue to be endorsed. Since that report was published, two newer classes of drugs, angiotensin-converting enzyme (ACE) inhibitors and calcium channel blockers, have been used by some practitioners.
The report states that ACE inhibitors have been found to be effective in children, especially younger ones. However, birth defects have been associated with the use of this class of drugs, so the report urges caution in using ACE inhibitors in adolescent girls who may be sexually active. Practical considerations such as tablet strength have limited the use of calcium channel blockers in children. Additionally, because of recent concerns about short-acting calcium channel blockers in adults, it has been recommended that physicians exercise caution in their use.
At present, there are no long term data available on the benefits and risks of antihypertensive drug therapy in children and adolescents. Thus, the treatment guidelines for children with hypertension are conservative and focus on health-related behavior changes. Cardiovascular diseases exact a substantial toll on the health of the population, contributing to 42% of all deaths. Many of the habits and behaviors that increase the risk of developing cardiovascular diseases, including hypertension, are established in childhood. With that public health perspective, the report urges the promotion of healthy behaviors for all children and their families.
To reach Dr. Falkner for comment, please contact Eryn Dobeck at Allegheny University Communications, (215) 842-4533.