Understanding Orthostatic Hypertension in Children

What Is Orthostatic Hypertension?

Orthostatic hypertension (OHT) is the term used to describe a notable elevation in blood pressure (BP) when an individual changes from a supine to an upright position. This phenomenon indicates the improper regulation of BP during postural adjustments. In adults, It is also associated with target organ damage and a poor prognosis. Zhao et al. first reported pediatric OHT in 2012, noting that most affected children were in puberty and experienced dizziness and syncope, often induced by sudden changes in position or prolonged standing. Studies suggest that OHT may heighten the risk of hypertension in young adults, and OHT is recognized as a significant cause of orthostatic intolerance (OI) in children.

How to Measure Orthostatic Blood Pressure?

To measure orthostatic blood pressure, the following steps are followed:

Step 1: Ask the patient to lie down and rest for five minutes.

Step 2: Record the pulse rate and blood pressure.

Step 3: Have the patient stand up.

Step 4: Re-measure the blood pressure and pulse rate after standing for one to three minutes.

If the patient experiences lightheadedness or dizziness, if their blood pressure drops by 20 millimeters of mercury (mm Hg) or more, or if their diastolic blood pressure drops by 10 mm Hg or more, the result is considered abnormal.

What Causes Orthostatic Hypertension in Children?

• Sympathetic Overactivation: The pathogenesis of orthostatic hypertension (OHT) in children has been unclear. Recent studies have suggested that sympathetic overactivation in an upright posture affects the development of orthostatic hypertension in children. This is supported by a decrease in baroreflex sensitivity and an increase in the low-frequency or high-frequency ratio of R-R interval variability when moving from a supine to an upright position. The decrease in baroreflex sensitivity reflects vagal activity in the baroreflex, while the increase in the low-frequency or high-frequency ratio of R-R interval variability indicates sympathetic predominance. Additionally, higher plasma antidiuretic hormone levels have been observed in children with postural tachycardia syndrome and OHT, and this increase may cause the development of orthostatic hypertension.

• Vascular Endothelial Injury: Other studies have shown that lower levels of plasma nitric oxide and nitric oxide synthase activity are associated with OHT in children, indicating vascular endothelial injury.

• Vitamin D Deficiency: Vitamin D deficiency has also been implicated as a possible risk factor for pediatric OHT. The mechanisms of OHT in adults include elevated norepinephrine levels, abnormal baroreflex, and changes in vascular properties, as well as the standing posture itself. However, differences in the mechanisms between pediatric and adult OHT need to be researched.

How Is Orthostatic Hypertension Diagnosed in Children?

The diagnosis of OHT can be made using several methods, such as the HUTT, the active standing test, BP self-measurement at home, and 24-hour ambulatory BP monitoring. OHT can be diagnosed by observing an increase in BP from supine to upright or by the absolute value of upright BP. The active standing test is a simple and safe method, while the HUTT is commonly used for differential diagnosis of OI causes in children. However, the HUTT carries the risk of syncope, requiring informed consent and appropriate protective measures. Home BP self-measurement and 24-hour ambulatory BP monitoring can effectively eliminate the bias of "white-coat hypertension," but their use in pediatric OHT diagnosis is limited due to practical difficulties.

The suggested diagnostic criteria for pediatric OHT include a normal supine BP, an increased SBP (systolic blood pressure) of more than or equal to 20 mm Hg, and or an increased DBP (diastolic blood pressure) of more than or equal to 25 mm Hg (in children 6 to 12 years old) or an increased DBP of more than or equal to 20 mm Hg (in adolescents 13 to 18 years old), or BP more than or equal to 130/90 mm Hg (in children 6 to 12 years old) or more than or equal to 140/90 mm Hg (in adolescents 13 to 18 years old) during the initial three minutes of the standing test or the HUTT.

The HUTT Test- The HUTT stands for head-up tilt table test. It is a medical diagnostic test used to evaluate syncope (fainting) and orthostatic intolerance (OI) in patients. The test involves the patient lying on a table that is then tilted upwards to a 60 to 80-degree angle, simulating an upright position. The patient's blood pressure, heart rate, and symptoms are monitored during the test. The HUTT helps diagnose the causes of syncope and OI, such as reflex syncope, orthostatic hypotension, and postural tachycardia syndrome.

Active Standing Test- It involves having the patient lie down for at least five minutes and then stand up for up to ten minutes while their blood pressure and heart rate are monitored. The AST is considered positive if there is a drop in systolic blood pressure (SBP) of at least 20 mm Hg or in diastolic blood pressure (DBP) of at least 10 mm Hg within three minutes of standing or if the patient experiences symptoms such as lightheadedness or dizziness.

How to Treat Orthostatic Hypertension in Children?

Previous studies on pediatric OHT have only reported non-drug treatments, such as autonomic nervous function exercise, health education, and wearing tights.

• Autonomic Nervous Function Exercise: This includes skin autonomic nervous training, standing training, aerobic exercise, and abdominal breath training, which has been found to reduce episodes of orthostatic intolerance symptoms.

• Health Education: This involves educating children on increasing water intake, avoiding sudden postural changes, and providing psychological assistance, which has shown a significant decrease in upright DBP (diastolic blood pressure).

• Wearing Tights: This has been suggested to increase cardiac output.

• Drugs: In elderly patients with OHT, oral administration of alpha-adrenergic blockers or Doxazosin has been found to reduce orthostatic BP, prevent target organ damage and improve symptoms. However, there is currently no recommended drug treatment for pediatric OHT.

Conclusion:

Orthostatic hypertension is a characteristic of blood pressure that occurs when standing and is associated with excessive neurohumoral activation. Orthostatic hypertension is a significant contributor to orthostatic intolerance in children and may lead to essential hypertension in the future. The condition is prevalent in older children, and its primary clinical symptoms are dizziness and syncope. Risk factors for pediatric orthostatic hypertension include insufficient water intake and sleep duration, a high body mass index, and increased red blood cell distribution width. The preferred method of treatment is non-pharmacological therapy, which has been shown to alleviate orthostatic intolerance symptoms effectively.