Ambulatory blood pressure monitoring: Improving the evaluation of hypertension in children
by Priya Pais, MD
Priya Pais, MD, is a pediatric nephrologist at Children's Hospital of Wisconsin. She also is an assistant professor of Pediatrics (Nephrology) at The Medical College of Wisconsin and a member of Children's Specialty Group.
Hypertension is the leading cause of premature death in adults throughout the world. Previously, pediatric hypertension was thought to be rare and mostly secondary in origin. However, it now is established that the rates of hypertension in children and adolescents, particularly primary or essential hypertension, are rising. (See Table 1.) Analyses of trends in childhood blood pressure verified that the increase in blood pressure is primarily due to the increase in obesity.
The definition of hypertension in adults is based on outcome data defining risk for adverse events. Such long-term data is not available for children. Therefore, the top percentiles of blood pressure distribution of pediatric normative data define hypertension. (See Table 2.)
www.nhlbi.nih.gov/guidelines/hypertension/child_tbl.pdf
Ambulatory blood pressure monitoring
Ambulatory blood pressure monitoring is a noninvasive outpatient technique used to obtain multiple blood pressure measurements over a prolonged period of time, typically 24 hours. The monitors are fully automatic and programmed to measure and record blood pressure, usually every 20 minutes. The monitors are worn on a belt and are connected by a plastic tube to a sphygmomanometer cuff on the upper arm. Specialized software is used to edit the 95th percentile ambulatory blood pressure monitoring cutoffs and interpret the patient's data.
Usually 60-70 readings are obtained from a successful ambulatory blood pressure monitoring study. Hypertension is diagnosed by comparing the patient's mean daytime and nighttime ambulatory blood pressure values with pediatric ambulatory normative data.
Ambulatory blood pressure monitoring can be used to make the following diagnoses:
White coat hypertension – This is a common condition in which blood pressure in the clinic is elevated but ambulatory blood pressures are normal. The use of ambulatory blood pressure monitoring in the initial evaluation of suspected childhood hypertension is highly cost-effective and can avert excessive testing and unnecessary therapy.
Masked hypertension – This is the opposite of white coat hypertension. It is defined as normal blood pressure in the clinic but elevated ambulatory levels. Masked hypertension should be suspected when blood pressure is elevated in some settings, but is normal in the clinic, or in patients with left ventricular hypertrophy but a normal blood pressure in the clinic.
Nocturnal hypertension – The mean ambulatory blood pressure normally falls 10-20 percent during periods of sleep, referred to as the nocturnal dip. The lack of a nocturnal dip or a rise in blood pressure during sleep is characteristic of secondary forms of hypertension and chronic kidney disease.
Inadequate therapeutic response – Ambulatory blood pressure monitoring also is used to adjust antihypertensive medications to achieve better blood pressure control.
Ambulatory blood pressure monitoring consistently has proved its superiority versus casual blood pressure measurements for predicting morbidity and mortality in adults. The Working Group on High Blood Pressure in Children and Adolescents now recognizes ambulatory blood pressure monitoring as a useful tool in the evaluation of hypertension in children. School-age children (older than age 8) tolerate ambulatory blood pressure monitoring well with minimal interference with daily activities and sleep. (See Table 3.)
Hypertension Clinic
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| Priya Pais, MD, reviews ambulatory blood pressure monitoring data for a patient using specialized software available to physicians at Children's Hospital of Wisconsin. |
New patients at least 8 years old are scheduled for their initial visit with the nurse practitioner. After obtaining a history and physical, an ambulatory blood pressure monitor is placed and arrangements are made for fasting labs to screen for kidney function and other comorbid conditions if the patient is overweight. The results of all testing are discussed with the patient's family during a follow-up visit with the nephrologist. Evaluation for secondary causes of hypertension and for target organ damage will be recommended if hypertension is confirmed by ambulatory blood pressure monitoring.
Patients prescribed antihypertensive medications are scheduled for regular follow-up visits to the clinic to make dose adjustments until the desired blood pressure goal has been reached, to assess adherence to therapy and to monitor for medication-related side effects.
Because obesity is so common in the hypertensive child, nonpharmacologic interventions also are discussed in detail with all patients. Patients meet with the dietitian to discuss weight loss and exercise goals and a healthy diet.
For more information, visit chw.org/nephrology.
To refer a patient, visit chw.org/refer or call toll-free (800) 266-0366.