Altered heart rhythm dynamics in very low birth weight infants with impending intraventricular hemorrhage

Sample entropy correlates with intraventricular hemorrhage and mortality in premature infants early in life

BACKGROUND

Mortality and intraventricular hemorrhage (IVH) are common adverse outcomes in preterm infants and are challenging to predict clinically. Sample entropy (SE), a measure of heart rate variability (HRV), has shown predictive power for sepsis and other morbidities in neonates. We evaluated associations between SE and mortality and IVH in the first week of life.

METHODS

Participants were 389 infants born before 32 weeks of gestation for whom bedside monitor data were available. A total of 29 infants had IVH grade 3 or 4 and 31 infants died within 2 weeks of life. SE was calculated with the PhysioNet open-source benchmark. Logistic regressions assessed associations between SE and IVH and/or mortality with and without common clinical covariates over various hour of life (HOL) censor points.

RESULTS

Lower SE was associated with mortality by 4 HOL, but higher SE was very strongly associated with IVH and mortality at 24-96 HOL. Bootstrap testing confirmed SE significantly improved prediction using clinical variables at 96 HOL.

CONCLUSION

SE is a significant predictor of IVH and mortality in premature infants. Given IVH typically occurs in the first 24-72 HOL, affected infants may initially have low SE followed by a sustained period of high SE.

IMPACT

SE correlates with IVH and mortality in preterm infants early in life. SE combined with clinical factors yielded ROC AUCs well above 0.8 and significantly outperformed the clinical model at 96 h of life. Previous studies had not shown predictive power over clinical models. First study using the PhysioNet Cardiovascular Toolbox benchmark in young infants. Relative to the generally accepted timing of IVH in premature infants, we saw lower SE before or around the time of hemorrhage and a sustained period of higher SE after. Higher SE after acute events has not been reported previously.

Heart Rate Characteristics Monitoring for Late-Onset Sepsis in Preterm Infants: A Systematic Review

BACKGROUND

Early diagnosis of late-onset sepsis (LOS) and necrotizing enterocolitis (NEC) by monitoring heart rate characteristics (HRC) of preterm infants might reduce the risk of death and morbidities. We aimed to systematically assess the effects of HRC monitoring on death, LOS, and NEC.

METHODS

A systematic search was performed in MEDLINE, Embase, Cochrane Library, and Web of Science.

RESULTS

Fifteen papers were included in this review. Three of these papers reported results from the only identified randomized controlled trial (RCT). This RCT showed that HRC monitoring resulted in a small but significant reduction in mortality (absolute risk reduction 2.1% [95% confidence interval 0.01-4.14]) without any differences in neurodevelopmental impairment. The risk of bias was rated high due to performance and detection bias and failure to correct for multiple testing. Most diagnostic cohort studies showed high discriminating accuracy in predicting LOS but lacked sufficient quality and generalizability. No studies for the detection of NEC were identified.

CONCLUSION

Supported by multiple observational cohort studies, the RCT identified in this systematic review showed that HRC monitoring as an early warning system for LOS might reduce the risk of death in preterm infants. However, methodological weaknesses and limited generalizability do not justify implementation of HRC in clinical care. A large international RCT is warranted.

The Effect of Caffeine on Heart Rate Variability in Newborns: A Pilot Study

Neonatal apnoea can be treated with caffeine, which affects the central nervous and cardiovascular systems. Heart rate variability (HRV) reflects the activity of the autonomic nervous system (ANS) and might be used as a measure of ANS maturation in newborns. We aimed to establish the effect of caffeine on HRV in newborns and investigated the potential correlation between HRV and postmenstrual age (PMA). In 25 haemodynamically stable newborns hospitalized due to apnoea and treated with caffeine (2.5 mg/kg), we assessed breathing frequency, arterial oxygen saturation, body temperature, and the heart rate while they were sleeping. We assessed HRV by spectral analysis using fast Fourier transformation. The same protocol was reapplied 100 h after caffeine withdrawal to assess the control parameters. Caffeine increased breathing frequency (p = 0.023) but did not affect any other parameter assessed including HRV. We established a positive correlation between postmenstrual age and HRV during treatment with caffeine as well as after caffeine had been withdrawn (total power: p = 0.044; low-frequency band: p = 0.039). Apparently, the maintenance dose of caffeine is too low to affect the heart rate and HRV. A positive correlation between PMA and HRV might reflect maturation of the ANS, irrespective of caffeine treatment.

Neonatal heart rate variability: a contemporary scoping review of analysis methods and clinical applications

BACKGROUND

Neonatal heart rate variability (HRV) is widely used as a research tool. However, HRV calculation methods are highly variable making it difficult for comparisons between studies.

OBJECTIVES

To describe the different types of investigations where neonatal HRV was used, study characteristics, and types of analyses performed.

ELIGIBILITY CRITERIA

Human neonates ≤1 month of corrected age.

SOURCES OF EVIDENCE

A protocol and search strategy of the literature was developed in collaboration with the McGill University Health Center's librarians and articles were obtained from searches in the Biosis, Cochrane, Embase, Medline and Web of Science databases published between 1 January 2000 and 1 July 2020.

CHARTING METHODS

A single reviewer screened for eligibility and data were extracted from the included articles. Information collected included the study characteristics and population, type of HRV analysis used (time domain, frequency domain, non-linear, heart rate characteristics (HRC) parameters) and clinical applications (physiological and pathological conditions, responses to various stimuli and outcome prediction).

RESULTS

Of the 286 articles included, 171 (60%) were small single centre studies (sample size <50) performed on term infants (n=136). There were 138 different types of investigations reported: physiological investigations (n=162), responses to various stimuli (n=136), pathological conditions (n=109) and outcome predictor (n=30). Frequency domain analyses were used in 210 articles (73%), followed by time domain (n=139), non-linear methods (n=74) or HRC analyses (n=25). Additionally, over 60 different measures of HRV were reported; in the frequency domain analyses alone there were 29 different ranges used for the low frequency band and 46 for the high frequency band.

CONCLUSIONS

Neonatal HRV has been used in diverse types of investigations with significant lack of consistency in analysis methods applied. Specific guidelines for HRV analyses in neonates are needed to allow for comparisons between studies.

Maturation of the cardiac autonomic regulation system, as function of gestational age in a cohort of low risk preterm infants born between 28 and 32 weeks of gestation

OBJECTIVES

The maturation of the sympathetic nervous system (SNS) occurs steadily throughout gestation while the myelinated vagus has accelerated maturation periods, between 25 and 32 weeks of gestation and a further increase around 37-38 weeks of gestation. The aim was to quantify the cardiac autonomic regulation maturation, as a function of gestational age (GA) in a cohort of low risk preterm infants born between 28 and 32 weeks of gestation by assessing heart rate variability (HRV) at week 32, and at week 35 postmenstrual age (PMA).

METHODS

Forty preterm infants were recruited, 24 h recordings of breathing rate and RR intervals were obtained at week 32 and week 35 PMA.

RESULTS

A significant difference was noted between preterm infants born before 32 weeks GA and preterm infants born at week 32; the latter present higher HRV values throughout the follow-up period. No significant change over time was noted for the parasympathetic HRV measures while a significant increase was found in the sympathetic system. Moreover, a significant interaction effect of time and system was found, the increase in values of the sympathetic system over time was significantly larger than the change noted in the vagal HRV measures.

CONCLUSIONS

Given the beneficial influence of vagal tone on health and developmental outcomes in preterm infants, the findings of the current study highlight the need for further studies on the impact of specifics gestational age on vagal development and later assessing interventions associate with its continue development and maturation at these specific periods.

Reproducibility of 24-h heart rate variability measures in preterm infants born at 28-32 weeks of gestation

AIMS

To determine the reproducibility and minimum detectable change (MDC) of heart rate variability (HRV) measures during two sequential 24-h periods, at week 32 of gestation, in preterm infants born between 28 and 32 weeks, hospitalized in the neonatal intensive care unit (NICU). The second aim is to assess postnatal changes in HRV measures between 32 and 35 weeks.

STUDY DESIGN

32 preterm infants born between 28 and 32 weeks of gestation were recruited. For each infant 48 h of recordings of RR interval were performed at week 32 and week 35. HRV parameters included time and frequency parameters.

RESULTS

At week 32, the intra-class correlation coefficient (ICC) of all HRV values was statistically significant with high correlation coefficients (ICC = 0.83-0.97). At week 35, a significant increase was noted in the HRV parameters, characterize mainly the sympathetic tone, with over half the infants showing an increase greater than the MDC for these parameters.

CONCLUSIONS

Using 24-h recording at week 32 of gestation during NICU routine is reliable, feasible, not costly and may have important implications for an early identification of premature in a state of stress such as sepsis, or as a follow-up measure.

Autonomic nervous system maturation in the premature extrauterine milieu

BACKGROUND

In premature infants, we investigated whether the duration of extrauterine development influenced autonomic nervous system (ANS) maturation.

METHODS

We performed a longitudinal cohort study of ANS maturation in preterm infants. Eligibility included birth gestational age (GA) < 37 weeks, NICU admission, and expected survival. The cohort was divided into three birth GA groups: Group 1 (≤29 weeks), Group 2 (30-33 weeks), and Group 3 (≥34 weeks). ECG data were recorded weekly and analyzed for sympathetic and parasympathetic tone using heart rate variability (HRV). Quantile regression modeled the slope of ANS maturation among the groups by postnatal age to term-equivalent age (TEA) (≥37 weeks).

RESULTS

One hundred infants, median (Q1-Q3) birth GA of 31.9 (28.7-33.9) weeks, were enrolled: Group 1 (n = 35); Group 2 (n = 40); and Group 3 (n = 25). Earlier birth GA was associated with lower sympathetic and parasympathetic tone. However, the rate of autonomic maturation was similar, and at TEA there was no difference in HRV metrics across the three groups. The majority of infants (91%) did not experience significant neonatal morbidities.

CONCLUSION

Premature infants with low prematurity-related systemic morbidity have maturational trajectories of ANS development that are comparable across a wide range of ex-utero durations regardless of birth GA.

IMPACT

Heart rate variability can evaluate the maturation of the autonomic nervous system. Metrics of both the sympathetic and parasympathetic nervous system show maturation in the premature extrauterine milieu. The autonomic nervous system in preterm infants shows comparable maturation across a wide range of birth gestational ages. Preterm newborns with low medical morbidity have maturation of their autonomic nervous system while in the NICU. Modern NICU advances appear to support autonomic development in the preterm infant.

Continuous vital sign analysis for predicting and preventing neonatal diseases in the twenty-first century: big data to the forefront

In the neonatal intensive care unit (NICU), heart rate, respiratory rate, and oxygen saturation are vital signs (VS) that are continuously monitored in infants, while blood pressure is often monitored continuously immediately after birth, or during critical illness. Although changes in VS can reflect infant physiology or circadian rhythms, persistent deviations in absolute values or complex changes in variability can indicate acute or chronic pathology. Recent studies demonstrate that analysis of continuous VS trends can predict sepsis, necrotizing enterocolitis, brain injury, bronchopulmonary dysplasia, cardiorespiratory decompensation, and mortality. Subtle changes in continuous VS patterns may not be discerned even by experienced clinicians reviewing spot VS data or VS trends captured in the monitor. In contrast, objective analysis of continuous VS data can improve neonatal outcomes by allowing heightened vigilance or preemptive interventions. In this review, we provide an overview of the studies that have used continuous analysis of single or multiple VS, their interactions, and combined VS and clinical analytic tools, to predict or detect neonatal pathophysiology. We make the case that big-data analytics are promising, and with continued improvements, can become a powerful tool to mitigate neonatal diseases in the twenty-first century.

Cerebral Oxygenation and Autoregulation in Very Preterm Infants Developing IVH During the Transitional Period: A Pilot Study

Background: The transitional period, defined as the first 72 h after preterm birth, is often characterized by a significant hemodynamic instability, which represents an important risk factor for such neurological complications of prematurity as intraventricular hemorrhage (IVH). The impairment of cerebral autoregulation plays a key role in the pathogenesis of IVH, whose incidence is highest during the transitional period. This pilot study aimed to evaluate whether patterns of cerebral autoregulation and oxygenation differ in relation to IVH development in very preterm infants during the transitional period. Methods: Infants <32 weeks' gestation were enrolled within 12 h from birth. A simultaneous monitoring of cerebral oxygenation (CrSO₂) by near-infrared spectroscopy and of heart rate and peripheral oxygen saturation by pulse oximetry was performed over the first 72 h. Cerebral fractional oxygen extraction (cFTOE) and tissue oxygenation-heart rate reactivity index (TOHRx), which represents a marker of cerebrovascular reactivity, were calculated. Daily cranial and cardiac ultrasound scans were performed, in order to assess the hemodynamic status and to detect a possible IVH onset. CrSO₂ and cFTOE, clustered on 6-hour epochs, were compared between infants who developed IVH during the study period and those who did not. A between-group comparison of TOHRx before and after IVH detection was also performed. Results: Twenty preterm infants with a median gestational age of 27 weeks (interquartile range, IQR: 25-30 weeks) and median birth weight of 895 g (IQR: 822-1208 g) were enrolled. Of these, 8 developed IVH. The median age at IVH detection was 40 h (IQR: 30-48 h). Pre-IVH TOHRx was significantly higher compared to matched control periods (p <0.001). CrSO₂ was significantly lower from 12 to 30 h and from 42 h onwards in cases compared to controls; however, a temporary CrSO₂ rise preceded IVH detection. Similarly, cFTOE was significantly higher in IVH infants from 12 to 30 h and from 48 to 72 h, with a transient decrease between the two periods. Conclusions: In preterm infants during the transitional period, the development of IVH is preceded by transient changes in cerebral oxygenation and oxygen extraction which, in turn, may underlie an early impairment of cerebral autoregulation. Larger studies are needed to confirm these preliminary findings.

Identifying an optimal epoch length for spectral analysis of heart rate of critically-ill infants

BACKGROUND AND OBJECTIVE

To identify the optimal epoch length for power spectral analysis of cardiac beat-to-beat intervals (BBi) in critically ill newborns.

MATERIALS AND METHOD

BBi of 49 term newborns undergoing therapeutic hypothermia for hypoxic-ischemic encephalopathy with well-defined outcomes (good outcome (n = 28): no or mild brain injury and adverse outcome (n = 21): moderate or severe brain injury or death) served as test population. A power spectrum of BBi was calculated with an autoregressive model in three different epoch lengths: 2 min, 5 min, and 10 min. Spectral power was quantified in three different frequency bands: very low-frequency (0.016-0.04 Hz), low-frequency (0.05-0.25 Hz), and high-frequency (0.3-1 Hz). In each frequency band, the absolute power and the normalized power were calculated. Furthermore, standard deviation (SDNN) of BBi was calculated. These metrics were compared between the outcome groups with a receiver operator characteristic (ROC) analysis in 3-h windows. The ROC curve area >0.7 was regarded as a significant separation.

RESULTS

The absolute spectral powers in all three epoch lengths in all three frequency bands and SDNN distinguished the two outcome groups consistently for most time points. The spectral metrics calculated with a 2-min epoch length performed as well as the five- and 10-min epoch lengths (paired t-test P < 0.05).

CONCLUSION

Spectral analysis of BBi in 2-min epoch shows a similar discriminatory power as longer epoch lengths. A shorter epoch also has clinical advantages for translation into a continuous real-time bedside monitor of heart rate variability in the intensive care unit.

Cardiovascular impact of intravenous caffeine in preterm infants

AIM

To evaluate the acute effect of intravenous caffeine on heart rate and blood pressure variability in preterm infants.

METHODS

We extracted and compared linear and nonlinear features of heart rate and blood pressure variability at two time points: prior to and in the two hours following a loading dose of 10 mg/kg caffeine base.

RESULTS

We studied 31 preterm infants with arterial blood pressure data and 25 with electrocardiogram data, and compared extracted features prior to and following caffeine administration. We observed a reduction in both scaling exponents (α₁ , α₂ ) of mean arterial pressure from detrended fluctuation analysis and an increase in the ratio of short- (SD1) and long-term (SD2) variability from Poincare analysis (SD1/SD2). Heart rate variability analyses showed a reduction in α₁ (mean (SD) of 0.92 (0.21) to 0.86 (0.21), p < 0.01), consistent with increased vagal tone. Following caffeine, beat-to-beat pulse pressure variability (SD) also increased (2.1 (0.64) to 2.5 (0.65) mmHg, p < 0.01).

CONCLUSION

This study highlights potential elevation in autonomic nervous system responsiveness following caffeine administration reflected in both heart rate and blood pressure systems. The observed increase in pulse pressure variability may have implications for caffeine administration to infants with potentially impaired cerebral autoregulation.

The Critical Role of the Central Autonomic Nervous System in Fetal-Neonatal Transition

The objective of this article is to understand the complex role of the central autonomic nervous system in normal and complicated fetal-neonatal transition and how autonomic nervous system dysfunction can lead to brain injury. The central autonomic nervous system supports coordinated fetal transitional cardiovascular, respiratory, and endocrine responses to provide safe transition of the fetus at delivery. Fetal and maternal medical and environmental exposures can disrupt normal maturation of the autonomic nervous system in utero, cause dysfunction, and complicate fetal-neonatal transition. Brain injury may both be caused by autonomic nervous system failure and contribute directly to autonomic nervous system dysfunction in the fetus and newborn. The central autonomic nervous system has multiple roles in supporting transition of the fetus. Future studies should aim to improve real-time monitoring of fetal autonomic nervous system function and in supporting typical autonomic nervous system development even under complicated conditions.

The biological embedding of neonatal stress exposure: A conceptual model describing the mechanisms of stress-induced neurodevelopmental impairment in preterm infants

The biological embedding of early life stress exposure may result in life-long neurodevelopmental impairment in preterm infants. Infants hospitalized in the neonatal intensive care unit are exposed to significant experiential, environmental, and physiologic stressors over the course of their extended hospitalization. Stress exposure during the sensitive period of brain development may alter biological processes, including functioning of the immune system, the autonomic nervous system, and the hypothalamic-pituitary-adrenal axis as well as gene expression. These alterations may subsequently affect brain structure and function. Changes to these processes may mediate the relationship between neonatal stress exposure and neurodevelopment in preterm infants and represent potential therapeutic targets to improve long-term outcomes. The purpose of this paper is to introduce a conceptual model, based on published research, that describes the mechanisms mediating stress exposure and neurodevelopment impairment in preterm infants and to provide the theoretical foundation on which to base future descriptive research, intervention studies, and clinical care.

Early Pulse Oximetry Data Improves Prediction of Death and Adverse Outcomes in a Two-Center Cohort of Very Low Birth Weight Infants

BACKGROUND

We previously showed, in a single-center study, that early heart rate (HR) characteristics predicted later adverse outcomes in very low birth weight (VLBW) infants. We sought to improve predictive models by adding oxygenation data and testing in a second neonatal intensive care unit (NICU).

METHODS

HR and oxygen saturation (SpO2) from the first 12 hours and first 7 days after birth were analyzed for 778 VLBW infants at two NICUs. Using multivariate logistic regression, clinical predictive scores were developed for death, severe intraventricular hemorrhage (sIVH), bronchopulmonary dysplasia (BPD), treated retinopathy of prematurity (tROP), late-onset septicemia (LOS), and necrotizing enterocolitis (NEC). Ten HR-SpO2 measures were analyzed, with first 12 hours data used for predicting death or sIVH and first 7 days for the other outcomes. HR-SpO2 models were combined with clinical models to develop a pulse oximetry predictive score (POPS). Net reclassification improvement (NRI) compared performance of POPS with the clinical predictive score.

RESULTS

Models using clinical or pulse oximetry variables alone performed well for each outcome. POPS performed better than clinical variables for predicting death, sIVH, and BPD (NRI > 0.5, p < 0.01), but not tROP, LOS, or NEC.

CONCLUSION

Analysis of early HR-SpO2 characteristics adds to clinical risk factors to predict later adverse outcomes in VLBW infants.

Big Data in Neonatal Health Care: Big Reach, Big Reward?

Analog-to-digital data conversion has created massive amounts of historical and real-time health care data. Costs associated with neonatal health issues are high. Big data use in the neonatal intensive care unit has the potential to facilitate earlier detection of clinical deterioration, expedite application of efficient clinical decision-making algorithms based on real-time and historical data mining, and yield significant cost-savings.

Autonomic nervous system depression at term in neurologically normal premature infants

BACKGROUND

Premature infants are vulnerable to destructive brain injury and disturbed neurological development. Prematurity may alter maturation of the central autonomic nervous system (ANS).

AIMS

To compare ANS function (using heart rate variability; HRV) between preterm infants with normal neuroimaging at term equivalent age and low-risk term controls. Study design, subjects. We performed a case-control study of preterm infants born ≤28 weeks gestational age that had normal brain imaging and archived continuous EKG data at term equivalent age. We documented other factors thought to influence ANS maturation (e.g. infection, ventilation days, and postnatal steroids). Controls were low-risk term gestational age newborns from uncomplicated pregnancies/deliveries. We characterized HRV metrics using frequency-(Welch periodogram) and time-domain (detrended fluctuation) analyses. Sympathetic tone was characterized by α1, root mean square analysis (RMS1 and RMS2), low-frequency (LF) power, and normalized LF (nLF) and parasympathetic tone was characterized by high-frequency (HF) power and normalized HF (nHF). α2 characterized ultraslow changes in heart rate. We used ANCOVA to compare HRV metrics between groups. Outcome measures, results. HRV from 26 preterm infants were compared to 55 controls. Analyzed HRV data for preterm infants were recorded at median (range) gestational age of 39 (36-39) weeks and for controls at 39 (37-41) weeks gestational age. α1, RMS2, LF and HF were significantly higher in control infants and remained significant after controlling for infection, ventilator days, and postnatal steroids (P < .005).

CONCLUSIONS

Autonomic maturation is impaired in a premature extrauterine environment. In the absence of destructive brain injury, our data suggest an important role for disturbed programming in this impaired autonomic development.

Surface electromyography for analysis of heart rate variability in preterm infants

OBJECTIVE

Characterizing heart rate variability (HRV) in neonates has gained increased attention and is helpful in quantifying maturation and risk of sepsis in preterm infants. Raw data used to derive HRV in a clinical setting commonly contain noise from motion artifacts. Thoracic surface electromyography (sEMG) potentially allows for pre-emptive removal of motion artifacts and subsequent detection of interbeat interval (IBI) of heart rate to calculate HRV. We tested the feasibility of sEMG in preterm infants to exclude noisy raw data and to derive IBI for HRV analysis. We hypothesized that a stepwise quality control algorithm can identify motion artifacts which influence IBI values, their distribution in the time domain, and outcomes of nonlinear time series analysis.

APPROACH

This is a prospective observational study in preterm infants  <6 days of age. We used 100 sEMG measurements from 24 infants to develop a semi-automatic quality control algorithm including synchronized video recording, threshold-based sEMG envelope curve, optimized QRS-complex detection, and final targeted visual inspection of raw data.

MAIN RESULTS

Analysis of HRV from sEMG data in preterm infants is feasible. A stepwise algorithm to exclude motion artifacts and improve QRS detection significantly influenced data quality (34% of raw data excluded), distribution of IBI values in the time domain, and nonlinear time series analysis. The majority of unsuitable data (94%) were excluded by automated steps of the algorithm.

SIGNIFICANCE

Thoracic sEMG is a promising method to assess motion artifacts and calculate HRV in preterm neonates.

Prediction of intraventricular haemorrhage in preterm infants using time series analysis of blood pressure and respiratory signals

Despite the decline in mortality rates of extremely preterm infants, intraventricular haemorrhage (IVH) remains common in survivors. The need for resuscitation and cardiorespiratory management, particularly within the first 24 hours of life, are important factors in the incidence and timing of IVH. Variability analyses of heart rate and blood pressure data has demonstrated potential approaches to predictive monitoring. In this study, we investigated the early identification of infants at a high risk of developing IVH, using time series analysis of blood pressure and respiratory data. We also explore approaches to improving model performance, such as the inclusion of multiple variables and signal pre-processing to enhance the results from detrended fluctuation analysis. Of the models we evaluated, the highest area under receiver-operator characteristic curve (5th, 95th percentile) achieved was 0.921 (0.82, 1.00) by mean diastolic blood pressure and the long-term scaling exponent of pulse interval (PI α₂), exhibiting a sensitivity of >90% at a specificity of 75%. Following evaluation in a larger population, our approach may be useful in predictive monitoring to identify infants at high risk of developing IVH, offering caregivers more time to adjust intensive care treatment.

Sex-related differences in the development of fetal heart rate dynamics

BACKGROUND

Despite previous efforts to explain the general advantages of female fetuses over males regarding health, sex-related differences in the dynamics or complexity of fetal heart rate (FHR) variability and FHR maturation patterns have not yet been identified.

AIM

To make linear and nonlinear comparisons of antepartum FHR indices, dynamics, complexity, and reactivity to the non-stress test (NST) and vibroacoustic-stimulation test (VAST) in male and female fetuses.

STUDY DESIGN

A total of 3835 singleton term deliveries without maternal and fetal complications were divided into female (n=1849) and male (n=1986) groups, and subjected to comparison and analyses.

SUBJECTS

Linear FHR indices, approximate entropy (ApEn), sample entropy (SampEn), short-term/long-term exponents (α1/α2), correlation dimension (CD), NST and VAST criteria, and modified nonlinear reactive criteria (MNRC) were used to evaluate outcomes.

RESULTS

ApEn was consistently higher in female fetuses than in male ones. ApEn in female fetuses was maximal at 29-30 gestational weeks, while the increase in ApEn was delayed in male fetuses but more rapid, reaching its peak at 31-32 gestational weeks. In both sexes, CD increased up to term, and α2 rapidly decreased up to 31-32weeks in an analogous manner. The two sexes differed significantly in response to VAST at <31 gestational weeks and there was a structural difference in reactive patterns under MNRC.

CONCLUSIONS

Female fetuses exhibit greater heart rate dynamics in early gestational periods, suggesting that their cardiovascular system matures earlier than that of males. Male fetuses undergo a compensatory period of rapid change to catch up with females at term.

The effects of caffeine on heart rate variability in newborns with apnea of prematurity

OBJECTIVE

Apnea of prematurity is a common complication in premature newborns and caffeine is a widespread medication used to treat this complication. Caffeine may have adverse effects on the cardiovascular and central nervous system, yet its effects on the autonomic nervous system modulation of heart rate have not been studied in premature newborns, which was the objective of our study.

STUDY DESIGN

We prospectively studied 21 premature newborns who were treated with caffeine. We analyzed heart rate variability by power spectral density and by dynamic nonlinear analyses methods.

RESULT

There were no changes in heart rate, blood pressure or the autonomic nervous system tone following administration of caffeine, nor were the nonlinear dynamical properties of the system altered by caffeine.

CONCLUSION

Caffeine does not have detrimental effects on heart rate variability, heart rate or blood pressure in conventional doses given to premature newborns.

Abnormal heart rate characteristics are associated with abnormal neuroimaging and outcomes in extremely low birth weight infants

OBJECTIVE

Brain injury in preterm infants may lead to an inflammatory response and central nervous system dysfunction reflected by abnormal heart rate characteristics (HRC). We hypothesized that a continuously monitored HRC index reflecting reduced HR variability and decelerations correlates with abnormal neuroimaging and outcomes in extremely low birth weight infants (ELBW).

STUDY DESIGN

We analyzed the average HRC index within 28 days after birth (aHRC28) and head ultrasound (HUS) in 384 ELBW infants. In 50 infants with brain magnetic resonance imaging (MRI) and 70 infants with Bayley neurodevelopmental testing at 1 year of age, we analyzed the relationship between aHRC28, MRI abnormalities and low Bayley scores.

RESULT

aHRC28 was higher in infants with severe HUS abnormalities (2.65±1.27 for Grade III-IV intraventricular hemorrhage (IVH) or cystic periventricular leukomalacia (cPVL) versus 1.72±0.95 for normal or Grade I-II IVH, P<0.001). Higher aHRC28 was also associated with white matter damage on MRI and death or Bayley motor or mental developmental index <70. Associations persisted after adjusting for gestational age, birth weight and septicemia. For every one point increase in aHRC28, the odds ratio of death or Bayley score <70 was 2.45 (95% CI 1.46, 4.05, P<0.001).

CONCLUSION

A continuously monitored HRC index provides an objective, noninvasive measure associated with abnormal brain imaging and adverse neurologic outcomes in ELBW infants.

Maternal race, demography, and health care disparities impact risk for intraventricular hemorrhage in preterm neonates

OBJECTIVE

To determine whether risk factors associated with grade 2-4 intraventricular hemorrhage (IVH) differs between infants of African ancestry and white infants.

STUDY DESIGN

Inborn, appropriate for gestational age infants with birth weight 500-1250 g and exposure to at least 1 dose of antenatal steroids were enrolled in 24 neonatal intensive care units. Cases had grade 2-4 IVH and controls matched for site, race, and birth weight range had 2 normal ultrasounds read centrally. Multivariate logistic regression modeling identified factors associated with IVH across African ancestry and white race.

RESULTS

Subjects included 579 African ancestry or white race infants with grade 2-4 IVH and 532 controls. Mothers of African ancestry children were less educated, and white case mothers were more likely to have more than 1 prenatal visit and multiple gestation (P ≤ .01 for all). Increasing gestational age (P = .01), preeclampsia (P < .001), complete antenatal steroid exposure (P = .02), cesarean delivery (P < .001), and white race (P = .01) were associated with decreased risk for IVH. Chorioamnionitis (P = .01), 5-minute Apgar score <3 (P < .004), surfactant use (P < .001), and high-frequency ventilation (P < .001) were associated with increased risk for IVH. Among African ancestry infants, having more than 1 prenatal visit was associated with decreased risk (P = .02). Among white infants, multiple gestation was associated with increased risk (P < .001), and higher maternal education was associated with decreased risk (P < .05).

CONCLUSION

The risk for IVH differs between infants of African ancestry and white infants, possibly attributable to both race and health care disparities.

Patent ductus arteriosus in preterm infants is associated with cardiac autonomic alteration and predominant parasympathetic stimulation

BACKGROUND

Hemodynamic disorders in patent ductus arteriosus (PDA) may alter the stimulation of the autonomic nervous system.

AIM

The objective of this study was to analyze the orthosympathetic-parasympathetic balance in preterm infants with PDA.

STUDY DESIGN AND SUBJECTS

Patients were included from consecutive admissions to Amiens University Hospital from 2009 to 2011. We defined a PDA group and a Control group (echographic criteria). For each patient, three 4-minutes segments of ECG were recorded during quiet sleep and the RR chronologic series were extracted, and spectral (Fourier Transform) and time-domain analyses were performed. For each parameter of heart rate variability (HRV), average of three measures was determined and analysed.

RESULTS

Forty-four patients were included for analysis. The total HRV power, LF/HF ratio and SDNN were lower in the PDA group (n = 22, gestational age 28.2 w ± 1.9) than in the Control group (n = 22, gestational age 28.8 w ± 2). The decrease in LF power destabilized the autonomic balance in favour of parasympathetic stimulation. After adjustment for postconceptional age, PDA was still associated with parameters of autonomic neural stimulation.

CONCLUSION

These results suggest association of PDA with predominance of parasympathetic stimulation in preterm infants. The mechanisms of homeostasis in patients with PDA are very complex and involve both circulatory adaptations and control by autonomic pathway. If confirmed, our results could be interesting for future researches aiming to verify the interest of new targeted therapies for the management of PDA.

Detrended fluctuation analysis of blood pressure in preterm infants with intraventricular hemorrhage

Very preterm infants are at high risk of death and serious permanent brain damage, as occurs with intraventricular hemorrhage (IVH). Detrended fluctuation analysis (DFA) that quantifies the fractal correlation properties of physiological signals has been proposed as a potential method for clinical risk assessment. This study examined whether DFA of the arterial blood pressure (ABP) signal could derive markers for the identification of preterm infants who developed IVH. ABP data were recorded from a prospective cohort of 30 critically ill preterm infants in the first 1-3 h of life, 10 of which developed IVH. DFA was performed on the beat-to-beat sequences of mean arterial pressure (MAP), systolic blood pressure (SBP) and pulse interval, with short-term exponent (α1, for timescale of 4-15 beats) and long-term exponent (α2, for timescale of 15-50 beats) computed accordingly. The IVH infants were found to have higher short-term scaling exponents of both MAP and SBP (α1 = 1.06 ± 0.18 and 0.98 ± 0.20) compared to the non-IVH infants (α1 = 0.84 ± 0.25 and 0.78 ± 0.25, P = 0.017 and 0.038, respectively). The results have demonstrated that fractal dynamics embedded in the arterial pressure waveform could provide useful information that facilitates early identification of IVH in preterm infants.

Heart rate dynamics during acute pain in newborns

Autonomic nervous system modulation of heart rate is significantly altered during painful procedures in newborns. Most studies investigating pain employed only linear-based analysis methods, thus ignoring the complex, non-linear nature of heart rate control mechanisms. The emergences of dynamic, nonlinear analysis methods enable us to uncover information embedded in the fluctuations of heart rate not otherwise noticeable. Our objective was to examine how cardiac dynamics change in newborns who undergo heel lancing by analyzing linear and nonlinear characteristics of heart rate fluctuations. We used dynamic nonlinear analyses methods to reveal heart rate variability and complexity alterations during painful stimulus in newborns. Poincaré plots were applied to examine the dynamics of the system, sample entropy to investigate the complexity of the system, and detrended fluctuation analysis, to reveal the fractal properties of the system. Heart rate significantly increased (165 vs.123 beats per minute, p < 0.001) while variability decreased. Sample entropy and the quantitative measures of the Poincaré plots (SD1 and SD2) significantly decreased during heel lancing (0.75 vs. 1.0, p < 0.01; 6.4 vs. 12.8, p < 0.001; and 30.4 vs. 50.5, p < 0.01, respectively). Detrended fluctuation analysis showed a significant decrease in the short-term scaling exponent α1 (1.06 vs. 1.3, p < 0.001), and an increase in the long-term scaling exponent α2 (1.5 vs. 1.1, p < 0.001). Our results indicate altered complexity of heart rate variability during painful stimulus in newborns and disruption of the mechanisms that regularly control it. Such alterations resemble certain pathological conditions and may represent stress reaction.

Real-time analysis for intensive care: development and deployment of the artemis analytic system

The lives of many thousands of children born premature or ill at term around the world have been saved by those who work within neonatal intensive care units (NICUs). Modern-day neonatologists, together with nursing staff and other specialists within this domain, enjoy modern technologies for activities such as financial transactions, online purchasing, music, and video on demand. Yet, when they move into their workspace, in many cases, they are supported by nearly the same technology they used 20 years ago. Medical devices provide visual displays of vital signs through physiological streams such as electrocardiogram (ECG), heart rate, blood oxygen saturation (SpO(2)), and respiratory rate. Electronic health record initiatives around the world provide an environment for the electronic management of medical records, but they fail to support the high-frequency interpretation of streaming physiological data. We have taken a collaborative research approach to address this need to provide a flexible platform for the real-time online analysis of patients' data streams to detect medically significant conditions that precede the onset of medical complications. The platform supports automated or clinician-driven knowledge discovery to discover new relationships between physiological data stream events and latent medical conditions as well as to refine existing analytics. Patients benefit from the system because earlier detection of signs of the medical conditions may lead to earlier intervention that may potentially lead to improved patient outcomes and reduced length of stays. The clinician benefits from a decision support tool that provides insight into multiple streams of data that are too voluminous to assess with traditional methods. The remainder of this article summarizes the strengths of our research collaboration and the resulting environment known as Artemis, which is currently being piloted within the NICU of The Hospital for Sick Children (SickKids) in Toronto, Ontario, Canada. Although the discussion in this article focuses on a NICU, the technologies can be applied to any intensive care environment.

Integration of early physiological responses predicts later illness severity in preterm infants

Physiological data are routinely recorded in intensive care, but their use for rapid assessment of illness severity or long-term morbidity prediction has been limited. We developed a physiological assessment score for preterm newborns, akin to an electronic Apgar score, based on standard signals recorded noninvasively on admission to a neonatal intensive care unit. We were able to accurately and reliably estimate the probability of an individual preterm infant's risk of severe morbidity on the basis of noninvasive measurements. This prediction algorithm was developed with electronically captured physiological time series data from the first 3 hours of life in preterm infants (< or =34 weeks gestation, birth weight < or =2000 g). Extraction and integration of the data with state-of-the-art machine learning methods produced a probability score for illness severity, the PhysiScore. PhysiScore was validated on 138 infants with the leave-one-out method to prospectively identify infants at risk of short- and long-term morbidity. PhysiScore provided higher accuracy prediction of overall morbidity (86% sensitive at 96% specificity) than other neonatal scoring systems, including the standard Apgar score. PhysiScore was particularly accurate at identifying infants with high morbidity related to specific complications (infection: 90% at 100%; cardiopulmonary: 96% at 100%). Physiological parameters, particularly short-term variability in respiratory and heart rates, contributed more to morbidity prediction than invasive laboratory studies. Our flexible methodology of individual risk prediction based on automated, rapid, noninvasive measurements can be easily applied to a range of prediction tasks to improve patient care and resource allocation.