Heart rate and heart rhythm in healthy infants and children

Cardiac rate and rhythm in 141 healthy infants, toddlers and schoolchildren during 24 hour ambulatory electrocardiographic monitoring are reported. Maximal and minimal heart rate (1/min) in infants 1 to 5 months of age were 204 +/- 17 and 105 +/- 13, in infants 6 to 12 months of age 187 +/- 19 and 101 +/- 15; in toddlers 177 +/- 17 and 66 +/- 10; in schoolchildren 158 +/- 24 and 54 +/- 6. A sizeable proportion of children of all age groups showed patterns of sinus arrhythmias indistinguishable from second degree sinuatrial block. Supraventricular escape beats and escape rhythms were frequent as well. The longest RR interval was 1.03 +/- 0.16 sec. in infants, 1.20 +/- 0.25 sec. in toddlers, and 1.35 +/- 0.15 sec., respectively, in schoolchildren. Two % of infants, 7% of toddlers, and 6% of schoolchildren had episodes of second degree atrioventricular block type I (Wenckebach) at rest. Supraventricular extrasystoles were found in 38%, 13% and 26%, respectively, and uniform ventricular extrasystoles in 18%, 20% and 16%, respectively, of infants, toddlers and schoolchildren. These data, together with similar information in the literature, can be taken as basis for the evaluation of ambulatory electrocardiograms in children.     

The use of low-EPA fish oil for long-chain polyunsaturated fatty acid supplementation of preterm infants

Because docosahexaenoic acid (DHA) may be an essential nutrient for the visual and early cognitive development of preterm infants, DHA enrichment of preterm formulas has been recommended. This randomized trial was designed to study the n-6 and n-3 fatty acid status of healthy preterm infants fed a formula enriched with a low eicosapentaenoic-fish oil until 4 mo corrected age compared with that of infants fed a standard formula. A reference group of breast-fed infants was studied concurrently. The fatty acid content of red blood cell (RBC) phospholipid was assessed at enrollment, hospital discharge, expected term, and 3 and 6 mo postterm. The DHA content of RBC phospholipid was higher in infants fed the enriched versus the standard formula at hospital discharge, expected term, and 3 and 6 mo postterm. However, compared with infants fed the standard formula, infants fed the enriched formula had also higher RBC phospholipid eicosapentaenoic content (0.69 +/- 0.15% versus 0.25 +/- 0.12%, p < 0.001), and lower RBC phospholipid arachidonic acid content (15.1 +/- 0.93% versus 18.8 +/- 0.89%; p < 0.001). We conclude that supplementing preterm infants with low-eicosapentaenoic fish oil is effective in improving DHA status, but results in worsening of n-6 fatty acid status. We speculate that preterm infants may require a dietary supply of arachidonic acid as well as DHA if the same fatty acid status as that of breast-fed infants is to be achieved.     

Randomized, double-blind trial of long-chain polyunsaturated fatty acid supplementation with fish oil and borage oil in preterm infants

OBJECTIVE: To test the efficacy and safety of long-chain polyunsaturated fatty acid (LCPUFA) supplementation with gamma-linolenic acid, a precursor of arachidonic acid, and docosahexaenoic acid in preterm infants. STUDY DESIGN: Preterm (<35 weeks, < or =2000 g birth weight) infants (n=238) randomly assigned to unsupplemented or LCPUFA-supplemented formula to 9 months after term. The main outcome measure was the Bayley Mental and Psychomotor Indexes (MDI, PDI) at 18 months after term. Safety outcome measures were anthropometry (9 and 18 months), feed tolerance, infection, and clinical complications. RESULTS: There were no significant differences in neurodevelopment between groups overall. In preplanned subgroup analyses, LCPUFA-supplemented boys had significantly higher Bayley MDI than did control boys (difference, 5.7 points; 95% CI, 0.3 to 11.1; P=.04). LCPUFA-supplemented infants showed significantly greater weight gain (difference, 310 g; 95% CI, 30 to 590 g; P=.03) and length gain (difference, 1.0 cm; 95% CI, 0.02 to 1.9; P=.05) between birth and 9 months, with greater effect in boys (weight difference at 9 months, 510 g; 95% CI, 80 to 930 g; P=.02; length difference at 18 months, 1.8 cm; 95% CI, 0.1 to 1.8; P=.03). CONCLUSIONS: This trial, using the strategy of providing gamma-linolenic acid as a source of arachidonic acid, showed efficacy for growth and for neurodevelopment in boys, with no adverse effects. These data have important implications for LCPUFA-supplementation strategy in preterm infants.     

Daily metabolic rate in healthy infants

BACKGROUND: Previous estimates of daily metabolic rate in infants were based on short-term unstandardized measurements of energy expenditure (EE). OBJECTIVE: Determine 24-hour metabolic profiles in infants. METHODS: Energy expenditure (kcal/min by indirect calorimetry) and physical activity (oscillations in weight/min/kg body weight) were measured in 10 healthy infants (5.0+/-0.8 months, 68+/-3 cm, 7.3+/-0.8 kg) for 24 hours in the Enhanced Metabolic Testing Activity Chamber while allowing parental interaction. Energy intake, 24-hour EE, resting metabolic rate (RMR), and sleeping metabolic rate (SMR) (kcal/kg/day) were determined. In addition, extrapolated 24-hour EE, RMR, and SMR from the first 4 and 6 hours of data were compared with 24-hour measurements. RESULTS: Twenty-four-hour energy intake, EE, RMR, and SMR (mean+/-SD) were 78.2+/-17.6, 74.7+/-3.8, 65.1+/-3.5, and 60.3+/-3.9, respectively. EE and physical activity showed a decrease at 11:30 pm and a return to daytime levels by 5:30 am, suggesting a metabolic circadian rhythm. Extrapolated 24-hour EE, RMR, and SMR from the first 4 hours (72.2+/-6.6, 65.9+/-8.7, and 64.9+/-6.4) and 6 hours (74.8+/-6.7, 65.8+/-6.6, and 64.8+/-5.6) were similar to 24-hour measurements. CONCLUSIONS: An apparent circadian rhythm in metabolic rate and physical activity was detected by 24-hour measurements. Furthermore, shorter-term measurements of the variables were comparable with 24-hour values.     

Effect of fish oil supplementation on the n-3 fatty acid content of red blood cell membranes in preterm infants

Very low birth weight infants demonstrate significant reductions in red blood cell membrane docosahexaenoic acid (DHA, 22:6n-3) following delivery unless fed human milk. The purpose of the present study was to determine if a dietary source of DHA (MaxEPA, R. P. Scherer Corporation, Troy, MI) could prevent the decline in red blood cell phospholipid DHA in very low birth weight infants whose enteral feeding consisted of a preterm formula without DHA. Longitudinal data were obtained on membrane phospholipid DHA in both unsupplemented and MaxEPA-supplemented infants by a combination of thin-layer and gas chromatography. These infants (n = 39) ranged in age from 10 to 53 days at enrollment (0 time). At enrollment, phospholipid DHA and arachidonic acid (20:4n-6) were inversely correlated with age in days. During the study, mean red blood cell phospholipid DHA declined without supplementary DHA as determined by biweekly measurement, but infants supplemented with MaxEPA maintained the same weight percent of phospholipid (phosphatidylethanolamine, phosphatidylcholine, and phosphatidylserine) DHA as at enrollment. The pattern of red blood cell phospholipid fatty acids in supplemented infants was similar to that reported for preterm infants fed human milk.     

健康足月新生儿生后10分钟内血氧饱和度及心率研究

目的探讨健康足月新生儿在出生后10 min内血氧饱和度(SpO2)及心率(HR)的变化及参考值。方法采用脉压氧饱和度仪测定203例正常足月新生儿(阴道产97例,剖宫产106例)在正常呼吸时的血SpO2及HR,描绘SpO2及HR在生后1~10分钟的第10~95百分位图表。结果生后第1分钟,健康新生儿血SpO2的P10、P50和P95分别为62%、71%和85%;HR的P10、P50和P95分别为66次/min、98次/min和126次/min。SpO2上升至90%的中位数时间为5 min。健康新生儿在出生后1~5 min HR随时间上升趋势明显,之后趋于平稳。结论可参考SpO2及HR,并结合临床表现综合评估新生儿,谨慎用氧,避免高氧或低氧血症对新生儿造成的损伤。     

The effect of iron supplementation on visual-evoked potentials in infants with iron-deficiency anemia.

Flash visual-evoked potentials were studied in 20 infants with iron-deficiency anemia to determine the effect of iron deficiency on visual function by using visual-evoked potentials in this type of anemia. After iron therapy for 12 weeks, visual-evoked potentials were retested in these otherwise healthy infants. All infants showed an excellent hematological response to iron therapy. Post-treatment visual-evoked potential N2 latencies (negative deflections) decreased significantly compared to the pre-treatment values (p < 0.05). These results suggest that iron-deficiency anemia causes subclinical visual impairment, and visual-evoked potentials may be a useful non-invasive means of detecting subtle effects of nutritional deficiencies and monitoring the nutritional status of infants.     

Maternal vitamin D deficiency and vitamin D supplementation in healthy infants

The objective of this study was to evaluate the common effects of maternal vitamin D deficiency, various doses of vitamin D given to newborns and the effects of these on vitamin D status in early childhood. Seventy-eight pregnant women and 65 infants who were followed up in various health centers were included in the sudy. 25-hydroxyvitamin-D (25-OHvitD), calcium (Ca), phosphorus (P) and alkaline phosphatase levels were measured in blood samples drawn from pregnant women in the last trimester. Infants born to these mothers were given 400 or 800 IU of vitamin D subsequently at the start of the second week. 25-OHvitD, Ca, P and alkaline phosphatase levels of the 65 infants who were brought in for controls (May-September 2000) were measured and hand-wrist X-rays were evaluated. We analyzed the relationship between vitamin D status of the mothers and infants and socio-economic status; mothers' dressing habits (covered vs uncovered), educational level, and number of pregnancies; and sunlight exposure of the house. Covered as a dressing habit meant covering the hair and sometimes part of the face and wearing dresses that completely cover the arms and legs. In 40 infants who were breast-fed and received the recommended doses of vitamin D on a regular basis, the relationship between serum vitamin D levels and supplementation doses given was analyzed. Serum 25-OHvitD level of the mothers was 17.50 +/- 10.30 and 94.8% of the mothers had a 25-OHvitD level below 40 nmol/L (below 25 nmol/L in 79.5%). The risk factors associated with low maternal 25-OHvitD were low educational level (p = 0.042), insufficient intake of vitamin D within diet (p = 0.020) and "covered" dressing habits (p = 0.012). 25-OHvitD level of the infants was 83.70 +/- 53.70 nmol/L, and 24.6% of the infants had 25-OHvitD levels lower than 40 nmol/L. Risk factors for low 25-OHvitD levels in infants were a) not receiving recommended doses of vitamin D regularly (p = 0.002) and b) insufficient sunlight exposure of the house (p = 0.033). There was a pour but significant correlation between maternal vitamin D levels and infants' 25-OHvitD levels at four months (r = 0.365, p < 0.05). No significant correlation was found between 25-OHvitD levels and supplementation doses of vitamin D (19 infants were supplemented with 400 IU/day and 21 with 800 IU/day of vitamin D) (p = 0.873). Severe maternal vitamin D deficiency remains a commonly seen problem in Turkey. However, vitamin D deficiency can be prevented by supplementation of vitamin D to newborns (at least 400 IU). Supplementation of 800 IU vitamin D in the areas of maternal vitamin D deficiency has no greater benefits for the infants.     

The effects of swaddling on oxygen saturation and respiratory rate of healthy infants in Mongolia

BACKGROUND: Infant swaddling is common practice in some developing countries where infant respiratory morbidity is also prevalent. Little is known about the effect of swaddling on respiratory variables in healthy infants. Such information could have important implications for respiratory diseases. AIMS: To compare respiratory rates (RR) and arterial oxygen saturations (SaO2) of healthy swaddled infants and non-swaddled infants during different conditions of sleep and arousal. SETTING: Community based, nested case control study in Ulaanbaatar, Mongolia. SUBJECTS AND METHODS: Habitually swaddled and non-swaddled infants aged 9-10 weeks taking part in a randomised controlled trial of swaddling. Respiratory rate and SaO2 were measured during quiet wakefulness, feeding, quiet and active sleep. Habitually swaddled infants were studied in swaddled and non-swaddled conditions. Habitually non-swaddled infants were studied only in the non-swaddled state. RESULTS: SaO2 was higher during awake states compared with sleep states in all groups of infants. Habitually swaddled infants had lower mean SaO2 in the swaddled compared with non-swaddled condition (96.5% vs. 96.9%, p < 0.01) but these were not significantly different from the mean SaO2 of non-swaddled infants (96.9%, minimum p = 0.22). Habitually swaddled infants in the swaddled and non-swaddled states had similar respiratory rates, but these were, in both cases, significantly lower than in habitually non-swaddled infants. CONCLUSION: Swaddling has little or no clinical effect on SaO2 or respiratory rates in healthy 9-10-week-old infants in Mongolia.     

Respiratory modulation of heart rate in newborn infants

Spectral analysis was performed on ventilation and instantaneous heart rate data recorded in 15 term infants during quiet sleep in the first week after delivery, and in 11 of these infants during active sleep. There was a close relation between the main peaks of the ventilation spectra and the corresponding histograms of the reciprocals of Ttot. The spectra for instantaneous heart rate showed power at the rate of breathing (HF) and also at lower frequencies, 0.04-0.2 Hz (LF). During quiet sleep, the relative magnitudes of the HF and LF peaks for heart rate were found to depend on the respiratory rate and the variability of Ttot. During active sleep, most of the power in the heart rate spectrum was concentrated in the LF region. Weighted coherences between ventilation and heart rate were higher during quiet than active sleep, both in the HF and LF spectra. LF power was higher during active than quiet sleep in both ventilation and heart rate. The results suggest that the pattern of breathing has a marked effect on the shape of the heart rate spectrum. In most infants, however, there is no fixed phase relationship between oscillations in ventilation and heart rate, at high or low frequencies. These oscillations are affected by sleep state and hence, by implication, by central nervous system rhythm generators.     

Fish oil supplementation improves docosahexaenoic acid status of malnourished infants

AIM—To investigate whether the low docosahexaenoic acid (DHA) status of malnourished, mostly breast fed, Pakistani children can be improved by fish oil (FO) supplementation.
METHODS—Ten malnourished children (aged 8-30 months) received 500 mg FO daily for nine weeks. The supplement contained 62.8 mol% (314mg) long chain polyunsaturated fatty acids of the ω3 series (LCPUFAω3) and 22.5 mol% (112 mg) DHA. Seven FO unsupplemented children served as controls. Red blood cell (RBC) fatty acids were analysed at baseline and at the study end.
RESULTS—FO supplementation augmented mean (SD) RBC DHA from 2.27 (0.81) to 3.35 (0.76) mol%, without significantly affecting the concentrations of LCPUFAω6. Unsupplemented children showed no RBC fatty acid changes. One FO supplemented child with very low initial RBC arachidonic acid showed a remarkable increase from 4.04 to 13.84 mol%, whereas another with high RBC arachidonic acid showed a decrease from 15.64 to 10.46 mol%.
CONCLUSION—FO supplementation improves the DHA status of malnourished children. The supplement is apparently well absorbed and not exclusively used as a source of energy.

     

Development of baroreflex influences on heart rate variability in preterm infants

To investigate developmental changes in autonomic cardiovascular reflexes in preterm infants, we used autoregressive power spectral analysis to analyze the effect of upright tilting on heart rate variability in preterm infants. Twenty-eight infants were studied in a longitudinal fashion beginning at 28-32 weeks postconceptional age (postnatal age 1-5 weeks). Each week, heart rate variability in the supine position and after 45 degrees head-up tilt was analyzed by spectral analysis. With the initial study of each infant, there was no significant change in heart rate following head-up tilt compared with baseline (-0.5+/-0.9 bpm). However, linear regression analysis revealed that with increasing postnatal age, the change in heart rate in response to tilting became more positive (mean slope of regressions 0.45+/-0.12 bpm/week, P<0.005). The power spectral density of R-R interval variability in the low-(LF; 0.02-0.15 Hz) and high-(HF; 0.15-1.5 Hz) frequency ranges were obtained and the values normalized by dividing each component by the total power. For measurements obtained in the supine position, the LF/HF ratio progressively decreased with increasing postnatal age, indicating a maturational change in sympathovagal balance. We used the difference in the LF/HF ratio between tilt and the recumbent position as a measure of the change in autonomic input to the heart in response to unloading of the arterial baroreceptors. No significant change in these ratios were observed when infants were first studied between 28 and 32 weeks postconceptional age, suggesting that the cardiac baroreflex is poorly developed at this stage of development. However, with postnatal maturation, the LF component of the power spectrum became progressively larger with tilt relative to the basal state, such that the difference between LF/HF(tilt) and LF/HF(base) became progressively more positive (P <0.006). These findings suggest that in premature infants, cardiac baroreceptor reflexes become more functional with postnatal development.     

Fish oil supplementation improves docosahexaenoic acid status of malnourished infants.

AIM: To investigate whether the low docosahexaenoic acid (DHA) status of malnourished, mostly breast fed, Pakistani children can be improved by fish oil (FO) supplementation. METHODS: Ten malnourished children (aged 8-30 months) received 500 mg FO daily for nine weeks. The supplement contained 62.8 mol% (314 mg) long chain polyunsaturated fatty acids of the omega3 series (LCPUFAomega3) and 22.5 mol% (112 mg) DHA. Seven FO unsupplemented children served as controls. Red blood cell (RBC) fatty acids were analysed at baseline and at the study end. RESULTS: FO supplementation augmented mean (SD) RBC DHA from 2.27 (0.81) to 3.35 (0.76) mol%, without significantly affecting the concentrations of LCPUFAomega6. Unsupplemented children showed no RBC fatty acid changes. One FO supplemented child with very low initial RBC arachidonic acid showed a remarkable increase from 4.04 to 13.84 mol%, whereas another with high RBC arachidonic acid showed a decrease from 15.64 to 10.46 mol%. CONCLUSION: FO supplementation improves the DHA status of malnourished children. The supplement is apparently well absorbed and not exclusively used as a source of energy.     

心肌炎患儿与正常儿童心率及心率变异性比较分析

目的 研究不同年龄心肌炎患儿的心率及心率变异性(HRV)改变的特点和相关性.方法 对120例心肌炎患儿进行24 h全程动态心电图检查,与804例正常儿童的心率及HRV进行比较分析.结果 7岁以下患儿最慢心率较正常增快,最快心率比较变化无差异,7～18岁患儿心率监测指标均异常;3～7岁心肌炎患儿与正常儿童比较每5分钟R-R间期平均值的标准差(SDANN)无变化,各组其他HRV指标均降低.结论 心肌炎患儿的HRV普遍降低,提示心脏自主神经系统的总体功能受损,以迷走神经张力降低为主,交感神经张力相对增强.     

Influences on heart rate variability in spontaneously breathing preterm infants.

To investigate the influence of maturational and physiological factors on heart rate variability in spontaneously breathing very preterm infants (n = 29) a multiparametric study was performed during the first 3 days of life in infants born at a gestational age below 33 weeks. Four times a day, RR-intervals, respiration curve and rate, transcutaneously measured blood gases and observed body movements were recorded while the infants were asleep. All data were stored simultaneously in a micro-computer. Non-invasively measured blood pressure and patency of the ductus arteriosus were documented as well. Four sets of short- (STV) and long term variability (LTV) indices were calculated. Both STV and LTV appeared to be significantly influenced by conceptional and postnatal age in the appropriate for gestational age infants. LTV was influenced by the behavioural state and body movements. During state coincidence 2 ('active sleep') LTV was influenced by respiratory rate and the variations in transcutaneous PO2. An effect of blood pressure or ductus patency could not be demonstrated.     

The influence of respiratory distress syndrome on heart rate variability in very preterm infants.

In a multi-parametric study the influence of pathological neonatal conditions on heart rate variability was investigated in 60 preterm infants born at a gestational age below 33 weeks. Measurements were performed during the first 3 days of life. Four times a day, RR-intervals, respiration curve and rate, transcutaneously measured blood gases and observed body movements were recorded while the infants were asleep. All data were stored simultaneously in a micro-computer. Severity of respiratory distress syndrome (RDS), patency of ductus arteriosus and periventricular haemorrhage were documented as well. Four sets of short- (STV) and long-term variability (LTV) indices were calculated. Severe RDS was associated with a significant decrease in LTV. The influence of RDS on LTV persisted after correction for conceptional age, postnatal age, behavioural state and variations in respiratory rate and in transcutaneous PO2. Infants with a symptomatic patent ductus arteriosus had lower LTV than controls with the same severity of RDS. STV was predominantly influenced by postnatal and conceptional age, and tended to be lower in infants with periventricular haemorrhage.