Reference ranges for blood pressure in preschool Australians, obtained by oscillometry

The Get-Up! study: adiposity and blood pressure in Australian toddlers

BACKGROUND

Because the elevated blood pressure (BP) in childhood is strongly associated with overweight and is a risk factor for later cardiovascular disease, a need to comprehend the early development of BP and its association with overweight is needed. We assessed differences of BP by weight status in Australian toddlers.

METHODS

From the Get-Up! Study in Australia, this sample included 265 toddlers (136 boys), aged 19.6 ± 4.2 months. BP was measured with a digital vital signs monitor. Participants were categorized as nonoverweight and overweight according to the World Health Organization definition for body mass index (BMI). Physical activity was captured with activPAL accelerometers, during childcare hours. To test differences in BP between nonoverweight and overweight children, we performed an analysis of covariance adjusting for sex, age, physical activity, and socioeconomic status.

RESULTS

Children with overweight showed higher z systolic BP values (P = .042 for BMI and P = .023 for waist circumference) when compared to nonoverweight children. However, no differences were found for z diastolic BP levels, between overweight and nonoverweight children. After adjustments for potential confounders (socioeconomic status, physical activity, sex, and age), there were no significant differences in BP variables between BMI and waist circumference groups.

CONCLUSIONS

No associations between adiposity and BP levels were found in this sample. The unadjusted results, however, showed that children with higher levels of adiposity (BMI and waist circumference) exhibited higher levels of BP. Additional research is needed to determine which environmental and genetic factors might contribute to pediatric hypertension, particularly among toddlers.

A comparison of clinical paediatric guidelines for hypotension with population-based lower centiles: a systematic review

Background

Different definitions exist for hypotension in children. In this study, we aim to identify evidence-based reference values for low blood pressure and to compare these with existing definitions for systolic hypotension.

Methods

We searched online databases until February 2019 (including MEDLINE, EMBASE, Web of Science) using a comprehensive search strategy to identify studies that defined age-related centiles (first to fifth centile) for non-invasive systolic blood pressure in healthy children < 18 years. Existing cut-offs for hypotension were identified in international guidelines and textbooks. The age-related centiles and clinical cut-offs were compared and visualized using step charts.

Results

Fourteen studies with population-based centiles were selected, of which 2 addressed children < 1 year. Values for the fifth centile differed 8 to 17 mmHg for age. We identified 13 clinical cut-offs of which only 5 reported accurate references. Age-related cut-offs for hypotension showed large variability (ranging from 15 to 30 mmHg). The clinical cut-offs varied in agreement with the low centiles. The definition from Paediatric Advanced Life Support agreed well for children < 12 years but was below the fifth centiles for children > 12 years. For children > 12 years, the definition of Parshuram’s early warning score agreed well, but the Advanced Paediatric Life Support definition was above the fifth centiles.

Conclusions

The different clinical guidelines for low blood pressure show large variability and low to moderate agreement with population-based lower centiles. For children < 12 years, the Paediatric Advanced Life Support definition fits best but it underestimates hypotension in older children. For children > 12 years, the Advanced Paediatric Life Support overestimates hypotension but Parshuram’s cut-off for hypotension in the early warning score agrees well. Future studies should focus on developing reference values for hypotension for acutely ill children.

Comparison of haematology and biochemistry parameters in healthy South African infants with laboratory reference intervals

Objective

Paediatric laboratory reference intervals used in Africa and Asia may be derived from historical intervals of predominantly Caucasian infants in Europe or North America. These intervals may therefore not be compatible with the range of normality for developing country populations. We aimed to compare haematology and biochemistry parameters in healthy South African infants with local laboratory reference intervals.

Methods

We compared the baseline haematology and biochemistry results of 634 (316 male and 318 female) HIV‐unexposed infants, aged 3–6 months, living in a rural area of the Western Cape Province, South Africa, against laboratory reference intervals supplied by the South African National Health Laboratory Services (NHLS). We calculated the percentage of observed values out of bound (in terms of lower and upper limits) compared to laboratory reference intervals.

Results

Of the 634 healthy infants screened, 316 (49.84%) were male and 318 (50.16%) female. A majority (91.05%) had platelet counts above the laboratory reference interval upper limit (350 × 10⁹cells/l), while over half, 54.85% and 56.98% had mean corpuscular volume (MCV) and mean corpuscular haemoglobin (MCH) values below the lower limits of 77.0–105.0 fl and 26.0–34.0 pg, respectively. A small proportion were outside the reference limits for haematocrit, namely 15.71% below and 7.14% above the normal limits of 0.31–0.38 l/l. For male and female infants, 33.65% and 18.04% of alkaline phosphatase (ALP) values and 7.01% and 14.56% of alanine transaminase (ALT) values were above the upper limits, respectively. For male infants, 10.83% of gamma‐glutamyl transferase (GGT) values, and for female infants, 31.11% of GGT values were below the lower limits of 12 U/l for males and 15 U/l for females. We observed no significant deviations (>10% out of bound) from NHLS reference intervals in the remaining haematology and biochemistry parameters measured.

Conclusions

Haematology and biochemistry parameters in apparently healthy South African infants deviate frequently from national laboratory reference intervals, including abnormalities consistent with subclinical hypochromic microcytic anaemia. It is important that clinical laboratory reference intervals for children are derived locally, rather than being adopted from Caucasian norms in developed countries, because clinical trials of vaccines, drugs and diagnostics are increasingly conducted in sub‐Saharan Africa.

Reference Values for Noninvasive Blood Pressure in Children during Anesthesia: A Multicentered Retrospective Observational Cohort Study

BACKGROUND

Although noninvasive blood pressure (NIBP) monitoring during anesthesia is a standard of care, reference ranges for blood pressure in anesthetized children are not available. We developed sex- and age-specific reference ranges for NIBP in children during anesthesia and surgery.

METHODS

In this retrospective observational cohort study, we included NIBP data of children with no or mild comorbidity younger than 18 yr old from the Multicenter Perioperative Outcomes Group data set. Sex-specific percentiles of the NIBP values for age were developed and extrapolated into diagrams and reference tables representing the 50th percentile (0 SD), +1 SD, -1 SD, and the upper (+2 SD) and lower reference ranges (-2 SD).

RESULTS

In total, 116,362 cases from 10 centers were available for the construction of NIBP age- and sex-specific reference curves. The 0 SD of the mean NIBP during anesthesia varied from 33 mmHg at birth to 67 mmHg at 18 yr. The low cutoff NIBP (2 SD below the 50th percentile) varied from 17 mmHg at birth to 47 mmHg at 18 yr old.

CONCLUSIONS

This is the first study to present reference ranges for blood pressure in children during anesthesia. These reference ranges based on the variation of values obtained in daily care in children during anesthesia could be used for rapid screening of changes in blood pressure during anesthesia and may provide a consistent reference for future blood pressure-related pediatric anesthesia research.

Preschool children blood pressure percentiles by age and height

We aimed to construct blood pressure (BP) references for the Polish preschool children and to compare them with the United States, German and European references. BP was measured oscillometrically using a validated device in 4378 randomly selected Polish children aged 3-6 years who were free of chronic diseases and behaved quietly during BP measurement. Height and weight were also measured. Gender-specific BP percentiles were constructed for age and height simultaneously with the use of quantile regression and a polynomial regression model. Systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial blood pressure reference percentiles by gender, age and height are presented. The Polish preschool children's 90th and 95th SBP and DBP percentiles were mostly lower than those in the United States, German and IDEFICS study BP references. Compared with the German oscillometric BP reference and with the United States sphygmomanometric BP reference, differences in the 95th SBP percentiles ranged by age from -5 to 0 mm Hg and from -2 to -1 mm Hg, in boys and girls, respectively, whereas the differences in the 95th percentiles of DBP ranged from -7 to -1 mm Hg and from -5 to -1 mm Hg, in boys and girls, respectively. Polish preschool children's BP percentiles based on measurements with the use of a validated oscillometric device in a nationally representative sample are lower than those from the current United States, German and European references. When interpreting BP measurements in children, adequate referential values should be used.

Blood pressure measurement at two years in offspring of women randomized to a trial of metformin for GDM: follow up data from the MiG trial

Background

Offspring born following maternal gestational diabetes are at risk of excessive childhood weight gain and Type 2 diabetes in childhood, which in turn is associated with an increased rate of hypertension.

We aimed to determine the systolic and diastolic blood pressure at two years of age in a cohort of children exposed to gestational diabetes mellitus using data from the MiG trial of metformin use in gestational diabetes. The secondary aim was to analyze these data by randomization of treatment to insulin or metformin.

Methods

The offspring of women who had gestational diabetes and had been assigned to either open treatment with metformin (with supplemental insulin if required) or insulin in the MiG trial were followed up at 2 years of age. Oscillometric measurement of BP in the right arm was performed by a researcher using an appropriately sized cuff.

Results

A total of 489 measurement blood pressure measurements were obtained in 170 of the 222 children who were seen at a median (range) age of 29 (22–38) months corrected gestational age. At the time of assessment the mean (SD) weight and height was 13.8(2) kg and 90 (4.2) cm respectively. For the whole group the mean (SD) systolic pressure was 90.9 (9.9) mmHg and mean (SD) diastolic pressure was 55.7 (8.1) mmHg. No difference was found between the metformin and insulin treatment arms. In a regression model, height and weight were only two factors associated with the levels of systolic blood pressure. For each additional kg the systolic blood pressure increased by 1.0 mmHg. For each additional cm of height the systolic blood pressure increased by 0.42 mmHg.

Conclusions

Blood pressure data was obtained at approximately two years of age in a substantial cohort of children whose mothers received treatment for GDM. These novel data compare favorably with published norms.

Clinical Trials Registry

This study was registered under the Australian New Zealand Clinical Trials Registry (ACTRN12605000311651).

Strengths and limitations of current pediatric blood pressure nomograms: a global overview with a special emphasis on regional differences in neonates and infants

The availability of robust nomograms is essential for the correct evaluation of blood pressure (BP) values in children. A literature search was conducted by accessing the National Library of Medicine by using the keywords BP, pediatric and reference values/nomograms. A total of 43 studies that evaluated pediatric BP nomograms were included in this review. Despite the accuracy of the latest studies, many numerical and methodological limitations still remain. The numerical limitations include the paucity of data for neonates/infants and for some geographic areas (Africa/South America/East Europe/Asia) and ethnicities. Furthermore, the data on ambulatory BP and response to exercise are extremely limited, and the criteria for stress-test interruption are lacking. There was heterogeneity in the methodologies employed to perform the measurements, in the inclusion/exclusion criteria (often not reported), in the data normalization and the data expression (Z-scores/percentiles/mean values). Although most studies adjusted the measurements for age and/or height, the classification by specific age/height subgroups varied. Gender differences were generally considered, whereas other confounders (that is, ethnicity/geographic area/environment) were seldom evaluated. As a result, nomograms were heterogeneous, and when comparable, at times showed widely different confidence intervals. These differences are most likely because of both methodological limitations and differences among the populations studied. Some robust nomograms exist (particularly those from the USA); however, it has been demonstrated that if adopted in other countries/continents, they may generate an unpredictable bias in the evaluation of BP values in children. Actual pediatric BP nomograms present consistent limitations that affect the evaluation of BP in children. Comprehensive nomograms, which are based on a large population of healthy children (including neonates/infants) and use standardized methodology, are warranted for every country/region.

Effect of peripheral edema on oscillometric blood pressure measurement

INTRODUCTION

Blood pressure (BP) measurement is essential for epidemiological studies and clinical decisions. It seems that tissue characteristics can affect BP results and we try to find edema effect on BP results taken by different methods.

METHODS

BP of 55 children before open heart surgery were measured and compared according to three methods: Arterial as standard and reference, oscillometric and auscultatory methods. Peripheral edema as a tissue characteristic was defined in higher than +2 as marked edema and in equal or lower than +2 as no edema.

STATISTICAL ANALYSES

data was expressed as Mean and 95% of confidence interval (CI 95%). Comparison of two groups was performed by T independent test and of more than two groups by ANOVA test. Mann-Whitney U and paired T-test were used for serially comparisons of changes. P less than 0.05 was considered significant.

RESULTS

Fifty five children aged 29.4±3.9 months were divided into two groups: 10 children with peripheral edema beyond +2 and 45 cases without edema. Oscillometric method overestimated systolic BP and the Mean (CI 95%) difference of oscillometric to arterial was 4.8 (8/-1, P=0.02) in edematous and 4.2 (7/1, p=0.004) in non edematous. Oscillometric method underestimated diastolic BP as -9 (-1.8/-16.5, P=0.03) in edematous group and 2.6 (-0.7/+5, P= 0.2) in non edematous compared to arterial method.

CONCLUSION

Oscillometric device standards cannot cover all specific clinical conditions. It underestimates diastolic BP significantly in edematous children, which was 9.2 mmHg in average beyond the acceptable standards.

Highlights for the management of a child with hypertension

Over the past several decades, childhood hypertension has undergone a considerable conceptual change, as hypertension is a predictor of future development of cardiovascular disease in adults. Childhood hypertension has distinctive features that distinguish it from hypertension in adults. Pediatric hypertension is often secondary. It is widely believed that therapeutic intervention at an early age favorably modifies the long-term outcome of hypertension. Despite its significance as a cause for morbidity, childhood hypertension is underdiagnosed and less studied with many basic issues remaining contentious.

A simplified table improves the recognition of paediatric hypertension

AIM

Unrecognised and untreated hypertension can lead to significant morbidity and mortality over time. In a 2003 chart review, we found that our providers only recognised 15% of hypertensive blood pressure (BP). Our objective was to determine whether a simplified BP table improves the recognition of elevated BP in children.

METHODS

We developed a simplified BP table for children 3-18 years and posted it in provider work areas beginning August 2006. We reviewed a retrospective sample of well visits for children aged 3-18 years, with equal numbers by sex and year of age, presenting at a university-based paediatric clinic between January and August 2007. Visit notes for all children with elevated BP values ≥ 90th percentile were reviewed to identify whether the provider recognised that the BP was elevated.

RESULTS

In 493 well visits, 85 (17.2%) children had pre-hypertensive (90th to < 95th percentile) and 100 (20.3%) had hypertensive (≥ 95th percentile) BP values. Providers recognised elevations in 34 (40%) pre-hypertensive and 77 (77%) hypertensive measurements. Recognition was significantly more common for those in the hypertensive than the pre-hypertensive range (χ² = 24.9, degrees of freedom= 1, P < 0.001). Compared with our 2003 data, recognition of hypertensive BP values was significantly greater (77% vs. 15%) (t = 14.479, degrees of freedom = 98, P <0.001) after introduction of the simplified BP table.

CONCLUSIONS

Use of a simplified BP table can lead to significantly improved recognition of elevated BP in children.

Blood pressure references for Polish children and adolescents

The objective of this study was to develop age- and gender-specific reference ranges for blood pressure in a large national database on blood pressure levels throughout childhood and adolescence in young Poles. A prospective cross-sectional study was performed in 2002-2005 in the representative sampling sites, selected randomly from the entire Poland. Altogether, 6,447 school pupils, aged 7-18 years, were involved in the study of which 3,176 were boys and 3,271 were girls. Statistical analysis was performed using STATISTICA for Windows 7.1. The normal range of blood pressure, determined by age and the category of body height percentiles, revealed percentiles values which might serve as reference values to identify cases of high normal blood pressure (the mean blood pressure between 90th and 95th percentiles for age and gender) and hypertension (the mean blood pressure equals or exceeds the 95th percentiles on at least three occasions).

[Blood pressure measurement in the German Health Interview and Examination Survey for Children and Adolescents (KiGGS). Methodology and initial results]

Hypertension is one of the main risk factors for cardiovascular disease and ranks among the leading causes of morbidity and mortality worldwide. Hypertension in children is rare, but the blood pressure rank in relation to peers is often maintained from childhood into adulthood and is therefore of great public health relevance. For this reason, one of the aims of the German Health Interview and Examination Survey for Children and Adolescents (KiGGS) was to collect representative data on blood pressure in children aged 3 to 17 years, in order to create an epidemiological basis for a comprehensive analysis of blood pressure in children and adolescents in Germany. Two oscillometric blood pressure measurements were obtained using an automated device (Datascope Accutorr Plus) and two readings of systolic, diastolic and mean arterial pressure and of heart rate were obtained in a standardised fashion in 14.730 children (7203 girls and 7527 boys). The main aim of this article is a detailed description of the blood pressure measurement in KiGGS, which is important for the interpretation of our findings compared to other studies. Our initial results on the distribution of systolic and diastolic blood pressure confirm previous findings of increasing blood pressure with age and height and of higher systolic blood pressure levels among boys compared with girls from the age of 14 years.

Children under pressure: an underestimated burden?

Perspective on the paper by Jackson et al (see page 298)

Prenatal ultrasound biometry related to subsequent blood pressure in childhood

STUDY OBJECTIVE

To relate measures of fetal growth/size other than birth weight with subsequent blood pressure measured on the same individuals within the context of the "fetal origins of adult disease".

DESIGN

A prospective cohort study in which measurements of fetal dimensions obtained by serial ultrasound imaging between 18 and 38 weeks gestation were analysed with reference to systolic blood pressure measurements on the offspring at age 6 years.

SETTING

Perth, Western Australia.

PARTICIPANTS

A subgroup of 707 eligible mother-fetus pairs from a cohort of 2876 pregnant women and their offspring. The number of mother-fetus pairs varied at each gestational age and by measurement of fetal dimension. Subsequent blood pressure recordings were obtained on approximately 300 of the offspring at age 6 years.

MAIN RESULTS

The findings confirmed the inverse association between birth weight and systolic blood pressure at age 6. There was, also, an inverse relation between fetal femur length and systolic blood pressure at age 6, adjusted for current height. Furthermore, an inverse association was demonstrated between a statistically derived measure of fetal growth (conditional z score) between 18 and 38 weeks gestation and later systolic blood pressure at age 6. The effect sizes for all three relations were in the order of 1-2 mm Hg per standard deviation change.

CONCLUSION

The mechanisms underpinning the "fetal origins" hypothesis may be operative early in pregnancy and may be reflected in the length of the fetal femur in early to mid-pregnancy.

Statistical measures of foetal growth using linear mixed models applied to the foetal origins hypothesis

Statistical models of the relationship between the distribution of each of five foetal dimensions and gestational age are developed based on serial ultrasound biometric data from a prospective longitudinal study in Perth, Western Australia. Both the response variable and the gestational age timescale are transformed to establish an approximately linear relationship within subjects. This relationship is modelled using a linear mixed effects model that accounts for between-subject heterogeneity by incorporating subject specific random effects for both intercept and gradient. These models are used to motivate three measures of foetal growth: the conditional centile or z-score of a current measurement given an earlier value for the same measurement; the best linear unbiased predictor (BLUP) of the subject specific random effect gradient (which is shown to be invariant to transformations of location and scale), and the standardized residual at a given gestational age, which characterizes departures from the modelled growth trajectory. We illustrate how these three measures of growth might be applied to subsequent health outcomes in later life by relating growth in foetal abdominal circumference to blood pressure in children from the same cohort at six years of age. Foetuses whose summary measures indicate poor growth in abdominal circumference have higher blood pressure in early childhood, supporting the 'foetal origins' hypothesis that many chronic diseases of adulthood have their origins before birth.

Placental weight and placental ratio as predictors of later blood pressure in childhood

OBJECTIVE

A significant inverse relationship between blood pressure and birth weight is firmly established. This association may be the result of fetal adaptations to an adverse intrauterine environment. Further markers of intrauterine growth include the weight of the placenta and the placental ratio (the ratio of placental weight to birth weight). A number of studies suggest that a decreased placental weight or an elevated placental ratio may be independent risk factors for subsequent high blood pressure. The overall evidence for this is, however, inconclusive. The purpose of the present study was to clearly define the relationships between placental weight, placental ratio and subsequent blood pressure during childhood.

DESIGN

Prospective cohort study of 2507 singleton children, born at term during 1989-1992. Blood pressures were recorded at ages 1, 3 and 6 years, using a semi-automated oscillometric device.

RESULTS

Inverse relationships existed between both systolic and diastolic blood pressure and placental weight, adjusted for current weight at ages 1, 3 and 6 years. The relationships between placental weight and systolic blood pressure were statistically significant at ages 1 and 3 years. There was no consistent relationship between placental weight and later blood pressure within birth weight categories. No clinically or statistically significant association was seen between the placental ratio and either systolic or diastolic blood pressures at any age.

CONCLUSIONS

Birth weight, rather than placental weight or their ratio, is the early life factor most importantly related to subsequent blood pressure in childhood.

Adjustment for current weight and the relationship between birth weight and blood pressure in childhood

OBJECTIVE

To determine the role of current weight in mediating the relationship between birth weight and blood pressure within the context of the 'fetal origins' hypothesis.

DESIGN

Prospective cohort study of 2507 pregnant women and their singleton offspring, delivered live at term, in Perth, Western Australia between 1989 and 1992. The study commenced at 16 weeks gestation with serial weight and blood pressure measurements recorded through early childhood.

RESULTS

Inverse associations were found between birth weight and systolic blood pressure at ages 1, 3 and 6. The effect of birth weight on systolic blood pressure at age 6 reached statistical significance and was increased fourfold in magnitude to -2.3 mmHg [95% confidence interval = (-3.3 to -1.3), P < 0.01] after adjustment for current weight. The interaction term for birth weight and current weight was not statistically significant. Including intermediate weights did not produce a statistically significantly better model but did increase the magnitude of the estimated regression coefficient of birth weight on blood pressure, and only the birth weight and current weight terms were significant

CONCLUSIONS

Adjustment for current weight serves to highlight the relationship between birth weight and blood pressure in childhood. Nevertheless, birth weight, rather than birth weight adjusted for current weight, is still the relevant predictor of later blood pressure within the context of the 'fetal origins' hypothesis.