The spectrum of circadian blood pressure changes in type I diabetic patients.

BACKGROUND: The objective of the present study was to characterize the spectrum of circadian blood pressure changes in type I diabetes at different stages of nephropathy by using two monitorings in each patient in order to avoid intra-individual variability. PATIENTS AND METHODS: A total of 80 type I diabetic subjects and the same number of age, sex and awake mean blood pressure (BP)-matched controls were included. According to urinary albumin excretion, there were 57 normoalbuminurics, 15 persistent microalbuminurics and eight proteinurics. Two 24 h ambulatory blood pressure monitorings were performed at the same urinary albumin excretion stage in absence of antihypertensive treatment for each diabetic subject and for their respective control. Blood pressure and heart rate averages during 24 h, awake, sleep, and day: night ratio were calculated. RESULTS: Seven of the eight proteinuric subjects were hypertensives, whereas hypertension was absent in the normoalbuminuric and microalbuminuric groups. The intraindividual reproducibility in diabetics showed repeatability coefficients for the 24 h systolic and diastolic pressure of 33 and 42%, respectively. This reproducibility for the day: night ratio was generally worse, 57% for systolic and 59% for diastolic. A progressive increment in the mean ambulatory BP was observed across the three groups of diabetics and the differences in BP observed were most evident during the night-time period. Though no differences in the 24 h circadian pattern were present between the normoalbuminurics and their controls, nocturnal differences were observed, not only in microalbuminurics for systolic BP (P < 0.05), but also in proteinurics for both systolic BP (P < 0.01) as well as diastolic BP (P < 0.05). No differences were observed in heart rate among the diabetic groups. The non-dipping pattern in the two monitorings was observed in 80, 58, 18 and 10% of the proteinurics, microalbuminurics, normoalbuminurics and control groups, respectively. CONCLUSIONS: Persistent abnormal circadian variability seems to be an early and frequent characteristic of type I diabetics with an increased urinary albumin excretion. Although present in some normalbuminuric subjects, the frequency of this abnormality increases as the incipient nephropathy progresses. By the time proteinuria is established, nearly all subjects present the abnormal pattern.

[Circadian rhythms variability of arterial pressure: methodological aspects for the measurement]. / Variabilidad circadiana de la presión arterial: aspectos metodológicos para su estimación.

BACKGROUND: To study the differences among the methods used for estimating daytime and nighttime ambulatory blood pressure values, and to analyze their determinant factors. SUBJECTS AND METHODS: In 402 individuals mean values of systolic and diastolic blood pressure (SBP and DBP) during 24 h, daytime and nighttime, were calculated by three different methods: a) real-time, following a minidiary; b) long-time, having a nighttime period from 23:00 to 07:00 h, and a daytime one from 08:00 to 22:00 h, and c) short-time, having a nighttime period from midnight to 6:00 h, and a daytime one from 08:00 to 22:00 h. RESULTS: Daytime mean values of SBP and DBP were similar for the three methods. Nighttime mean values of SBP and DBP calculated using the long-time were significantly higher than those calculated with the real-time ((SBP -2.25 [5.3] mmHg, p < 0.05; DBP -1.17 [3.4] mmHg, p < 0.05). No differences were observed for both SBP and DBP with the real-time. The number of sleeping hours was the main determinant of the differences observed between the long-time and the real-time methods. The percentage of subjects with a non-dipping pattern were 17, 26 and 18% for real, long and short time methods, respectively. CONCLUSIONS: Daytime mean BP values are reproducible whatever the method used, but for estimating nighttime mean BP values short-time is the best of the fixed-time methods. Minidiary should be used if more accurate values are necessary or if the subjects sleep habits do not fit into the standard patterns.

The impact of obesity and body fat distribution on ambulatory blood pressure in children and adolescents.

To assess the relationship between obesity, body fat distribution, and blood pressure in children and adolescents, various measures of obesity and the waist-to-hip circumference ratio were related to casual and ambulatory blood pressure as measured using a SpaceLabs 90207 monitor during a regular school day. Seventy obese and 70 nonobese children aged 6 to 16 years were included in the study. Regardless of the time period analyzed (24 h, daytime, or nighttime), ambulatory blood pressure and casual blood pressure were significantly higher among the obese children. The differences in systolic blood pressure observed between the groups were attributable to the presence of obesity as estimated by the ponderal index and by skinfold thickness. Similarly, systolic and diastolic loads, as an assessment of high blood pressure values over 24 h, were significantly higher in the obese children when compared to the loads for the nonobese children. Waist-to-hip circumference ratio was independently associated, (in multiple regression analysis) with systolic blood pressure, whether during 24 h, daytime, or nighttime periods, after controlling for age, sex, current height, ponderal index, and tricipital skinfold thickness. This study demonstrates that obesity is a determinant of ambulatory and casual blood pressure. Since obese children with a predominantly abdominal fat mass show higher blood pressure values, evaluation of body fat distribution in children may help to identify subjects more susceptible to developing hypertension later in life.

Current and birth weights exert independent influences on nocturnal pressure-natriuresis relationships in normotensive children.

The objective was to study the impact of birth weight on the relationship between ambulatory blood pressure and urinary sodium excretion in children and adolescents. The study included 134 healthy children (61 boys), all Caucasians, who were born at term after a normotensive pregnancy. For each subject, a 24-hour ambulatory blood pressure monitoring and a complete urine collection were simultaneously performed according to the protocols designed. Average ambulatory blood pressure (BP) and the urinary excretion rates for sodium, potassium, and creatinine were calculated separately for 24-hour, awake, and sleep periods defined by a mini-diary. The excretion rate of sodium during sleep time was positively correlated with ambulatory systolic BP; such a positive relationship was not found for waking hours. Consequently, the impact of birth weight on the relationship between blood pressure and the urinary sodium excretion rate was analyzed during sleeping hours. Stepwise multiple regression analysis shows that although current weight was the strongest predictor for the sodium excretion rate during sleep (P<.001), there was also an independent significant direct relationship for birth weight (P<.04) after controlling for age, sex, and the average of systolic BP during sleep. Adjusted for current weight, a significant difference in the regression slopes relating urinary sodium excretion rate and systolic BP during sleep exists between children in the lowest (<3.100 kg) and the highest tertiles (>3.500 kg) of birth weight (P<.02). Differences in sodium excretion rates, adjusted for current weight, between the two extreme tertiles of birth weight became significant at the highest systolic BP (P<.04). The children who had the lowest birth weight tended to excrete less sodium during sleep. The results of the present study show a blunted pressure natriuresis curve in children and adolescents with the lowest birth weight. Whether this abnormal renal sodium handling may be present as an initial or as an intermediate mechanism leading to higher BP values must be assessed in additional studies.

Relationship between birth weight and awake blood pressure in children and adolescents in absence of intrauterine growth retardation.

This study was designed to examine the relationship between birth weight (BW) and ambulatory blood pressure in children and adolescents, born at term in absence of intrauterine growth retardation. Twenty-four hour ambulatory blood pressure monitoring (ABPM) was performed on 332 children (150 boys), aged from 6 to 16 years. Subjects were stratified by BW tertiles and age. ABPM was performed using SpaceLabs 90207 monitor during a regular school day. Blood pressure (BP) was measured every 20 min from 06:00 to 24:00, and thereafter every 30 min. Means of systolic BP (SBP) and diastolic BP (DBP) during 24 h, daytime (08:00 to 22:00), and nighttime (24:00 to 06:00) were calculated. Systolic and diastolic load was estimated as the percentage of measurements above the age- and sex-specific 95th percentile during the 24 h. BW was inversely related to daytime (SBP (P = .04) and SBP load (P = .04) when controlled for sex, current height, ponderal index (weight/height3), and age. The predictive values of daytime SBP throughout the pediatric age group in the two extreme tertiles of BW (lowest, 2.500 to 3.200 kg; and highest, 3.501 to 4.820 kg) were obtained from regression equations including SBP during activity period or SBP load and age. Children who had lower BW tended to have higher daytime SBP or SBP load at any age although this difference was not statistically significant. These differences became more evident as the subjects got older. BW is a determinant of daytime SBP even in the absence of intrauterine growth retardation. The influence of BW seems to increase with age.

Diurnal blood pressure curve in children and adolescents.

OBJECTIVE: To investigate the diurnal blood pressure curve in healthy normotensive children. Thirty-one children were re-examined after a median interval of 123 days in order to study the reproducibility of the diurnal profile. SUBJECTS: Twenty-four-hour ambulatory blood pressure monitoring and conventional blood pressure readings were obtained in 228 normotensive children, whose ages ranged from 6 to 16 years and of whom 116 were boys and 112 girls. RESULTS: The conventional blood pressure averaged 99+/-11/57+/-9 mmHg in boys and 98+/-12/56+/-9 mmHg in girls (means+/-SD); the corresponding 24 h pressures were 111+/-7/66+/-5 mmHg and 109+/-7/65+/-5 mmHg, respectively. Of the children, 83% had a significant diurnal blood pressure rhythm for systolic pressure and 89% for diastolic pressure. The nocturnal blood pressure fall was normally distributed, averaging 12.0+/-6.3 mmHg systolic and 14.2+/-5.9 mmHg diastolic. There was no evidence for a bimodal distribution. The amplitude of the diurnal blood pressure curve, determined by the Fourier approach, was positively skewed with a mean of 12.5+/-4.2 mmHg for systolic and 14.0+/-4.1 mmHg for diastolic blood pressure. The daily blood pressure maximum occurred at 1344+/-4 h 46 min for systolic and 1321+/-4 h 22 min for diastolic blood pressure. For systolic blood pressure the cumulative sum (cusum)-derived circadian alteration magnitude was 1.7+/-6.2 mmHg higher in boys than in girls, whereas the cusum plot height was also 7.3+/-27.0 mmHg x h higher in male subjects. The repeatability coefficient (2SD of the difference between paired recordings, expressed as a percentage of nearly maximal variation) was 80% for the conventional systolic pressure and 40% for the conventional diastolic blood pressure. The repeatability coefficients for the ambulatory blood pressure levels varied from 32 to 45% and for the parameters describing the diurnal blood pressure profile from 42 to 78%. CONCLUSION: A significant diurnal blood pressure rhythm is observed in most normotensive children and adolescents. There is no evidence for a bimodal distribution of the nocturnal blood pressure fall. The reproducibility of the parameters of the diurnal blood pressure curve tended to be less than that of the ambulatory blood pressure level. Thus, one 24 h recording is probably insufficient to characterize a child's diurnal blood pressure profile fully.

[Ambulatory arterial blood pressure in normotensive children]. / Presión arterial ambulatoria en niños normotensos.

BACKGROUND: The aim of the present study was to obtain out patient blood pressure values in normotensive children based on age, height, and sex in order to determine reference values. METHODS: Out patient blood pressure monitorization was performed in 248 healthy normotensive children (129 males and 119 females, ages 6 to 16 years) (casual blood pressure < P95 specific for age and sex) over 24 hours by the Spacelabs 90207 oscilometric monitor on a normal schoolday. An appropriately sized armband was chosen for each case with the readings being programmed every 20 minutes between 6:00 a.m. and midnight and every 30 minutes for the remaining readings. The means of 24 hour blood pressure (all the readings obtained), day period (8 to 22 hours) and night period (midnight to 6:00 a.m.) and the circadian variability (difference and the ratio between the mean values of day and night) were calculated. The children were divided into subgroups according to sex, age (6-9, 10-12 and 13-16 years) and height (1.09-1.37; 1.38-1.51, and 1.52-1.75 meters). Monitorizations with a percentage of erroneous readings over 30% were excluded from the study. RESULTS: Only 7 children were excluded due to a high percentage of erroneous readings. The mean of the valid readings made in the remaining 241 cases was 62 +/- 7. A significant increase was observed in the values of out patients systolic blood pressure with age and height. The same was not seen in diastolic blood pressure. Nocturnal blood pressures were lower to the diurnal pressures (11% systolic, 22% diastolic). P95 was considered as the upper limit of normality for the means of each of the periods of systolic and diastolic blood pressure in each subgroup of sex, age and height. CONCLUSIONS: The blood pressure values obtained from a population of normotensive children may be useful to understand the behaviour of out patient blood pressure in children and establish the limit for defining high blood pressure.

Ambulatory blood pressure monitoring in normotensive children.

OBJECTIVE: To assess reference values of ambulatory blood pressure in normotensive children. SUBJECTS AND DESIGN: Twenty-four-hour non-invasive ambulatory blood pressure monitoring (ABPM) was carried out in 241 healthy normotensive children aged from 6 to 16 years (126 boys, mean +/- SD age 11.2 +/- 2.7 years; 115 girls, mean +/- SD age 10.9 +/- 2.9 years). The subjects were subdivided into three age-sex groups: 6-9, 10-12 and 13-16 years. SETTING: Primary care. MAIN OUTCOME MEASURES: ABPM was performed using an oscillometric device (SpaceLabs model 90207) and appropriate cuff size during a regular school day. Blood pressure was measured every 20 min from 0600 to 2400 h, and thereafter every 30 min. At each monitoring session the following parameters were calculated for both systolic (SBP) and diastolic blood pressure (DBP): means and centiles for 24-h, daytime (0800-2200 h) and night-time (2400-0600 h); circadian variability, estimated as the blood pressure fall between the day and the night periods and the day: night ratio; and load, as the percentage of measurements above the age- and sex-specific 95th centile (P95). RESULTS: The upper limits of 'normality' for the mean of 24-h SBP and DBP estimated as the P95 in each age subgroup were 121/71 and 119/71 mmHg, 123/78 and 120/74 mmHg, and 124/78 and 125/75 mmHg, for boys and girls, respectively. A progressive increase in SBP with age was observed in both sexes, in contrast, DBP was similar throughout the age range. A nocturnal blood pressure fall of approximately 11 mmHg was observed for both SBP and DBP in all subgroups. The day:night ratio was 1.12 and 1.22 for SBP and DBP, respectively. The upper limit of blood pressure load, estimated as the P95 in all children, was 39% for SBP and 26% for DBP. A significant positive correlation was observed between casual blood pressure and 24-h ambulatory blood pressure (SBP: r = 0.61, P < 0.0001; DBP: r = 0.31, P < 0.0001). In general, mean ambulatory blood pressure, during the 24-h or the daytime period, was higher than casual blood pressure for both SBP and DBP. CONCLUSION: ABPM is feasible in children, and the values obtained are useful as a departure point in establishing reference values.

Altered blood pressure during sleep in normotensive subjects with type I diabetes.

This study was designed to examine the circadian pattern of blood pressure in children and young adults with type I diabetes who were completely normotensive by standard criteria. Forty-five patients and the same number of age- and sex-matched control subjects were studied. In diabetic children of 10-14 years of age, the nocturnal fall in systolic and diastolic blood pressures was intact. In diabetics of 15-20 years of age, the fall in systolic blood pressure was blunted; in diabetics of 21-37 years of age, the fall in both systolic and diastolic blood pressures during sleep was blunted. When data from all diabetic subjects were pooled and analyzed in a multiple linear regression model, mean blood pressure during sleep correlated best with urinary albumin excretion (r = 0.60). On the basis of this finding, we subdivided our patients into two groups: a microalbuminuric group (urinary albumin excretion > 30 mg per 24 hours; mean, 160.3 +/- 29.7; n = 11) and a normoalbuminuric group (urinary albumin excretion < 30 mg per 24 hours; mean, 6.6 +/- 6.5; n = 34). Both systolic and diastolic blood pressures during sleep were higher in microalbuminuric (121.1 +/- 3.3 and 69.3 +/- 2.5 mm Hg, respectively) than in normoalbuminuric diabetics (114.2 +/- 1.8 and 60.1 +/- 1.2 mm Hg, p < 0.05) or control subjects (113.3 +/- 1.2 and 60.1 +/- 1.2 mm Hg, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)