Causes of low blood pressure in children

Blood Pressure

Blood pressure is the pressure carried on by circulating blood upon the walls of blood vessels. It is measured using a stethoscope, and a sphygmomanometer and is given in two records - systolic and diastolic pressure. Systolic pressure is the pressure of blood against the artery walls, while diastolic pressure is the pressure when the heart is resting between beats. Blood pressure readings in children, lower than 116-104 for systolic and 63-74 for diastolic, are in the realm of hypotension or low blood pressure.

In kids, height has a significant effect on blood pressure. Taller children tend to have higher blood pressure, so the normal blood pressure varies depending on a child’s age, gender, and constitution.

Until recently, low blood pressure was considered a problem only for the elderly population. However, The American Heart Association and the American Academy of Pediatrics suggest that kids have their blood pressure checked frequently, beginning at three years.

Types of Hypotension

Hypotension can be divided into three main categories: Orthostatic, also known as a head rush, occurs when changing from a sitting or prone position to standing. This type of hypotension usually increases with age.

Neurally mediated hypotension (NMH) points out a change in blood pressure while standing. This is especially common when standing for a long period.

Severe hypotension or shock naturally results from a sudden and excessive loss of blood after an accident or injury.

Causes of Low Blood Pressure

Low blood pressure takes place when blood pressure, during or after a heart beat, becomes lower than usual. Symptoms may sometimes fall behind, and often it does not require any treatment. However, fluctuations in blood pressure affect the brain, heart, and other vital organs in the process of receiving the blood supply needed for proper functioning.

Orthostatic hypotension is caused by sudden changes in posture, and it is quite rare in children. Neurally mediated hypotension, however, affects youngsters if they have been standing for a long time. Dehydration, illness, and certain medications may also cause low blood pressure.

Symptoms of Low Blood Pressure

Symptoms like dizziness, fainting, blurry vision, and light-headedness may point to hypotension. Symptoms usually disappear quickly, but it is of vital importance to respond appropriately and avoid injuries. The patient should lie down immediately and rise the feet above the heart level.

Recognizing blood pressure (BP) abnormalities in children is more cumbersome than in adults and contributes to underdiagnoses in pediatrics. While adult blood pressure thresholds are static, 140/90 mmHg for hypertension and 90/60 mmHg for hypotension, each child has his/her own BP thresholds based on gender, age, and height percentile. While BP tracks with growth in children, similar to anthropometric measurements such as height and weight, it is not currently charted in the same way using growth charts. Instead complex BP tables consisting of 476 threshold blood pressure values are used to lookup the BP percentile for a child. Often these tables are used incorrectly or not at all.

The American Academy of Pediatrics has endorsed NHLBI guidelines that recommend all children over 3 years of age have BP measured at least annually for early recognition of BP abnormalities such as hypertension or syncope, although studies have shown this screening is rarely done in children.
Since height accounts for substantially more BP variability than age and is a more direct measure of body size and maturation in children, height-specific BP percentile curves were drawn separately for males and females. We used the 2004 Fourth Report data source and equations to calculate the BP threshold value for each gender and 5 cm height group. By slightly underestimating a child’s BP percentile for high BP and slightly overestimating a child’s BP percentile for low BP, these charts guarantee 100 % sensitivity in detecting abnormal BP. Sensitivity and specificity of the chart cut-offs were confirmed in a sample of 1254 healthy children from a school-based blood pressure screening program.
The 1st, 5th, 25th, 50th, 75th, 90th, 95th, and 99th BP percentile curves are depicted in the chart for each corresponding gender and height from 85 to 190 cm, mimicking the ubiquitous CDC “growth charts”. Shaded areas of the chart differentiate abnormal BP status categories: hypotension, normal BP, prehypertension, Stage 1 hypertension, and Stage 2 hypertension. Sensitivity was confirmed to be 100 % with specificity above 94 %.

These simplified BP charts improve upon currently available BP screening reference with the following features: (a) tracking BP longitudinally in an individual child, (b) full physiological range of BP percentiles represented in percentile curve format for rapid identification both high and low BP, (c) easy to use with absolute height alone avoiding the additional step of determining height percentile, (d) incorporation of adult threshold for pre-hypertension to assist in accurate transition from adolescence into adulthood, (e) high sensitivity and specificity to ensure all children at risk are identified with very few false positives.

✓ Fact confirmed: Blood pressure percentile charts to identify high or low blood pressure in children Ashish Banker, Cynthia Bell, Monesha Gupta-Malhotra, and Joshua Samuels; 2016 Jul 19.

Treatment and Prevention

Individuals prone to low blood pressure should try to avoid triggers and treat the underlying cause of low blood pressure. For example, if the medications cause fluctuations in blood pressure, patients should change the dosage. An extra salty diet may also help, together with drinking many fluids.

It is important to slowly change body position and avoid standing for long periods. Regular blood checks at different ages, starting from three years, are strongly advised.