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

Heart Rate and Pulse Oximetry Dynamics in the First Week after Birth in Neonatal Intensive Care Unit Patients and the Risk of Cerebral Palsy

OBJECTIVE

 Infants in the neonatal intensive care unit (NICU) are at high risk of adverse neuromotor outcomes. Atypical patterns of heart rate (HR) and pulse oximetry (SpO2) may serve as biomarkers for risk assessment for cerebral palsy (CP). The purpose of this study was to determine whether atypical HR and SpO2 patterns in NICU patients add to clinical variables predicting later diagnosis of CP.

STUDY DESIGN

 This was a retrospective study including patients admitted to a level IV NICU from 2009 to 2017 with archived cardiorespiratory data in the first 7 days from birth to follow-up at >2 years of age. The mean, standard deviation (SD), skewness, kurtosis and cross-correlation of HR and SpO2 were calculated. Three predictive models were developed using least absolute shrinkage and selection operator regression (clinical, cardiorespiratory and combined model), and their performance for predicting CP was evaluated.

RESULTS

 Seventy infants with CP and 1,733 controls met inclusion criteria for a 3.8% population prevalence. Area under the receiver operating characteristic curve for CP prediction was 0.7524 for the clinical model, 0.7419 for the vital sign model, and 0.7725 for the combined model. Variables included in the combined model were lower maternal age, outborn delivery, lower 5-minute Apgar's score, lower SD of HR, and more negative skewness of HR.

CONCLUSION

 In this study including NICU patients of all gestational ages, HR but not SpO2 patterns added to clinical variables to predict the eventual diagnosis of CP. Identification of risk of CP within the first few days of life could result in improved therapy resource allocation and risk stratification in clinical trials of new therapeutics.

KEY POINTS

· SD and skewness of HR have some added predictive value of later diagnosis of CP.. · SpO2 measures do not add to CP prediction.. · Combining clinical variables with early HR measures may improve the prediction of later CP..

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.

Inflammatory biomarkers and physiomarkers of late-onset sepsis and necrotizing enterocolitis in premature infants

Background

Early diagnosis of late-onset sepsis (LOS) and necrotizing enterocolitis (NEC) in very low birth weight (VLBW, <1,500 g) infants is challenging due to non-specific clinical signs. Inflammatory biomarkers increase in response to infection, but non-infectious conditions also cause inflammation. Cardiorespiratory data contain physiological biomarkers, or physiomarkers, of sepsis that may be useful in combination with inflammatory hematologic biomarkers for sepsis diagnosis.

Objectives

To determine whether inflammatory biomarkers measured at the time of LOS or NEC diagnosis differ from times without infection and whether biomarkers correlate with cardiorespiratory sepsis physiomarkers in VLBW infants.

Methods

Remnant plasma sample collection from VLBW infants occurred with blood draws for routine laboratory testing and suspected sepsis. We analyzed 11 inflammatory biomarkers and a pulse oximetry sepsis warning score (POWS). We compared biomarker levels obtained at the time of gram-negative (GN) bacteremia or NEC, gram-positive (GP) bacteremia, negative blood cultures, and no suspected infection.

Results

We analyzed 188 samples in 54 VLBW infants. Several biomarkers were increased at the time of GN LOS or NEC diagnosis compared with all other samples. POWS was higher in patients with LOS and correlated with five biomarkers. IL-6 had 78% specificity at 100% sensitivity to detect GN LOS or NEC and added information to POWS.

Conclusions

Inflammatory plasma biomarkers discriminate sepsis due to GN bacteremia or NEC and correlate with cardiorespiratory physiomarkers.

Heart rate patterns predicting cerebral palsy in preterm infants

BACKGROUND

Heart rate (HR) patterns can inform on central nervous system dysfunction. We previously used highly comparative time series analysis (HCTSA) to identify HR patterns predicting mortality among patients in the neonatal intensive care unit (NICU) and now use this methodology to discover patterns predicting cerebral palsy (CP) in preterm infants.

METHOD

We studied NICU patients <37 weeks' gestation with archived every-2-s HR data throughout the NICU stay and with or without later diagnosis of CP (n = 57 CP and 1119 no CP). We performed HCTSA of >2000 HR metrics and identified 24 metrics analyzed on HR data from two 7-day periods: week 1 and 37 weeks' postmenstrual age (week 1, week 37). Multivariate modeling was used to optimize a parsimonious prediction model.

RESULTS

Week 1 HR metrics with maximum AUC for CP prediction reflected low variability, including "RobustSD" (AUC 0.826; 0.772-0.870). At week 37, high values of a novel HR metric, "LongSD3," the cubed value of the difference in HR values 100 s apart, were added to week 1 HR metrics for CP prediction. A combined birthweight + early and late HR model had AUC 0.853 (0.805-0.892).

CONCLUSIONS

Using HCTSA, we discovered novel HR metrics and created a parsimonious model for CP prediction in preterm NICU patients.

IMPACT

We discovered new heart rate characteristics predicting CP in preterm infants. Using every-2-s HR from two 7-day periods and highly comparative time series analysis, we found a measure of low variability HR week 1 after birth and a pattern of recurrent acceleration in HR at term corrected age that predicted CP. Combined clinical and early and late HR features had AUC 0.853 for CP prediction.

Inflammatory Biomarkers and Physiomarkers of Late-Onset Sepsis and Necrotizing Enterocolitis in Premature Infants

Background

Early diagnosis of late-onset sepsis (LOS) and necrotizing enterocolitis (NEC) in VLBW (<1500g) infants is challenging due to non-specific clinical signs. Inflammatory biomarkers increase in response to infection, but non-infectious conditions also cause inflammation in premature infants. Physiomarkers of sepsis exist in cardiorespiratory data and may be useful in combination with biomarkers for early diagnosis.

Objectives

To determine whether inflammatory biomarkers at LOS or NEC diagnosis differ from times without infection, and whether biomarkers correlate with a cardiorespiratory physiomarker score.

Methods

We collected remnant plasma samples and clinical data from VLBW infants. Sample collection occurred with blood draws for routine laboratory testing and blood draws for suspected sepsis. We analyzed 11 inflammatory biomarkers and a continuous cardiorespiratory monitoring (POWS) score. We compared biomarkers at gram-negative (GN) bacteremia or NEC, gram-positive (GP) bacteremia, negative blood cultures, and routine samples.

Results

We analyzed 188 samples in 54 VLBW infants. Biomarker levels varied widely, even at routine laboratory testing. Several biomarkers were increased at the time of GN LOS or NEC diagnosis compared with all other samples. POWS was higher in patients with LOS and correlated with five biomarkers. IL-6 had 78% specificity at 100% sensitivity to detect GN LOS or NEC and added information to POWS (AUC POWS = 0.610, POWS + IL-6 = 0.680).

Conclusions

Inflammatory biomarkers discriminate sepsis due to GN bacteremia or NEC and correlate with cardiorespiratory physiomarkers. Baseline biomarkers did not differ from times of GP bacteremia diagnosis or negative blood cultures.

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.

Omics approaches: interactions at the maternal-fetal interface and origins of child health and disease

Immunoperinatology is an emerging field. Transdisciplinary efforts by physicians, physician-scientists, basic science researchers, and computational biologists have made substantial advancements by identifying unique immunologic signatures of specific diseases, discovering innovative preventative or treatment strategies, and establishing foundations for individualized neonatal intensive care of the most vulnerable neonates. In this review, we summarize the immunobiology and immunopathology of pregnancy, highlight omics approaches to study the maternal-fetal interface, and their contributions to pregnancy health. We examined the importance of transdisciplinary, multiomic (such as genomics, transcriptomics, proteomics, metabolomics, and immunomics) and machine-learning strategies in unraveling the mechanisms of adverse pregnancy, neonatal, and childhood outcomes and how they can guide the development of novel therapies to improve maternal and neonatal health. IMPACT: Discuss immunoperinatology research from the lens of omics and machine-learning approaches. Identify opportunities for omics-based approaches to delineate infection/inflammation-associated maternal, neonatal, and later life adverse outcomes (e.g., histologic chorioamnionitis [HCA]).

Multivariable Predictive Models of Death or Neurodevelopmental Impairment Among Extremely Low Birth Weight Infants Using Heart Rate Characteristics

OBJECTIVE

We hypothesized that a cumulative heart rate characteristics (HRC) index in real-time throughout the neonatal intensive care unit (NICU) hospitalization, alone or combined with birth demographics and clinical characteristics, can predict a composite outcome of death or neurodevelopmental impairment (NDI).

STUDY DESIGN

We performed a retrospective analysis using data from extremely low birth weight infants who were monitored for HRC during neonatal intensive care. Surviving infants were assessed for NDI at 18-22 months of age. Multivariable predictive modeling of subsequent death or NDI using logistic regression, cross-validation with repeats, and step-wise feature elimination was performed each postnatal day through day 60.

RESULTS

Among the 598 study participants, infants with the composite outcome of death or moderate-to-severe NDI had higher mean HRC scores during their stay in the NICU (3.1 ± 1.8 vs 1.3 ± 0.8; P < .001). Predictive models for subsequent death or NDI were consistently higher when the cumulative mean HRC score was included as a predictor variable. A parsimonious model including birth weight, sex, ventilatory status, and cumulative mean HRC score had a cross-validated receiver-operator characteristic curve as high as 0.84 on days 4, 5, 6, and 8 and as low as 0.78 on days 50-52 and 56-58 to predict subsequent death or NDI.

CONCLUSIONS

In extremely low birth weight infants, higher mean HRC scores throughout their stay in the NICU were associated with a higher risk of the composite outcome of death or NDI.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT00307333.

Vital signs as physiomarkers of neonatal sepsis

Neonatal sepsis accounts for significant morbidity and mortality, particularly among premature infants in the Neonatal Intensive Care Unit. Abnormal vital sign patterns serve as physiomarkers of sepsis and provide early warning of illness before overt clinical decompensation. The systemic inflammatory response to pathogens signals the autonomic nervous system, leading to changes in temperature, respiratory rate, heart rate, and blood pressure. In infants with comorbidities of prematurity, vital sign abnormalities often occur in the absence of infection, which confounds sepsis diagnosis. This review will cover the mechanisms of vital sign changes in neonatal sepsis, including the cholinergic anti-inflammatory pathway mediated by the vagus nerve, which is critical to the host response to infectious and inflammatory insults. We will also review the clinical implications of vital sign changes in neonatal sepsis, including their use in early warning scores and systems to direct clinicians to the bedside of infants with physiologic changes that might be due to sepsis. IMPACT: This manuscript summarizes and reviews the relevant literature on the physiological manifestations of neonatal sepsis and how we monitor and analyze these through vital signs and advanced analytics.

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.

Autism risk in neonatal intensive care unit patients associated with novel heart rate patterns

BACKGROUND

Neonatal intensive care unit (NICU) patients are at increased risk for autism spectrum disorder (ASD). Autonomic nervous system aberrancy has been described in children with ASD, and we aimed to identify heart rate (HR) patterns in NICU patients associated with eventual ASD diagnosis.

METHODS

This retrospective cohort study included NICU patients from 2009 to 2016 with archived HR data and follow-up beyond age 3 years. Medical records provided clinical variables and ASD diagnosis. HR data were compared in infants with and without ASD.

RESULTS

Of the 2371 patients, 88 had ASD, and 689,016 h of data were analyzed. HR skewness (HRskw) was significantly different between ASD and control infants. Preterm infants at early postmenstrual ages (PMAs) had negative HRskw reflecting decelerations, which increased with maturation. From 34 to 42 weeks PMA, positive HRskw toward accelerations was higher in males with ASD. In 931 males with at least 4 days of HR data, overall ASD prevalence was 5%, whereas 11% in the top 5th HRskw percentile had ASD.

CONCLUSION

High HRskw in NICU males, perhaps representing autonomic imbalance, was associated with increased ASD risk. Further study is needed to determine whether HR analysis identifies highest-risk infants who might benefit from earlier screening and therapies.

IMPACT

In a large retrospective single-center cohort of NICU patients, we found that high positive skewness of heart rate toward more accelerations was significantly associated with increased risk of eventual autism spectrum disorder diagnosis in male infants but not in females. Existing literature describes differences in heart rate characteristics in children, adolescents, and adults with autism spectrum disorders, but the finding from our study in NICU infants is novel. Heart rate analysis during the NICU stay might identify, among an inherently high-risk population, those infants with especially high risk of ASD who might benefit from earlier screening and therapies.

Global incidence of intraventricular hemorrhage among extremely preterm infants: a systematic literature review

OBJECTIVES

To conduct a systematic literature review to evaluate the global incidence of intraventricular hemorrhage grade 2-4 among extremely preterm infants.

METHODS

We performed searches in MEDLINE and Embase for intraventricular hemorrhage and prematurity cited in English language observational studies published from May 2006 to October 2017. Included studies analyzed data from infants born at ≤28 weeks' gestational age and reported on intraventricular hemorrhage epidemiology.

RESULTS

Ninety-eight eligible studies encompassed 39 articles from Europe, 31 from North America, 25 from Asia, five from Oceania, and none from Africa or South America; both Europe and North America were included in two publications. The reported global incidence range of intraventricular hemorrhage grade 3-4 was 5-52% (Europe: 5-52%; North America: 8-22%; Asia: 5-36%; Oceania: 8-13%). When only population-based studies were included, the incidence range of intraventricular hemorrhage grade 3-4 was 6-22%. The incidence range of intraventricular hemorrhage grade 2 was infrequently documented and ranged from 5-19% (including population-based studies). The incidence of intraventricular hemorrhage was generally inversely related to gestational age.

CONCLUSIONS

Intraventricular hemorrhage is a frequent complication of extremely preterm birth. Intraventricular hemorrhage incidence range varies by region, and the global incidence of intraventricular hemorrhage grade 2 is not well documented.

Precision Medicine in Neonates: A Tailored Approach to Neonatal Brain Injury

Despite advances in neonatal care to prevent neonatal brain injury and neurodevelopmental impairment, predicting long-term outcome in neonates at risk for brain injury remains difficult. Early prognosis is currently based on cranial ultrasound (CUS), MRI, EEG, NIRS, and/or general movements assessed at specific ages, and predicting outcome in an individual (precision medicine) is not yet possible. New algorithms based on large databases and machine learning applied to clinical, neuromonitoring, and neuroimaging data and genetic analysis and assays measuring multiple biomarkers (omics) can fulfill the needs of modern neonatology. A synergy of all these techniques and the use of automatic quantitative analysis might give clinicians the possibility to provide patient-targeted decision-making for individualized diagnosis, therapy, and outcome prediction. This review will first focus on common neonatal neurological diseases, associated risk factors, and most common treatments. After that, we will discuss how precision medicine and machine learning (ML) approaches could change the future of prediction and prognosis in this field.

Habituation Alteration in Infants with Periventricular Echogenicity as an Indicator of Neurocognitive Impairment

Habituation difficulties may suggest neurocognitive impairment. Periventricular echogenicity (PVE) potentially causes subtle damage that poses neuropsychological risk. Habituation was evaluated through heart rate and behavioral states in infants at 36-37 weeks of corrected age between control and PVE groups. PVE infants showed early alertness and abrupt changes in behavioral states. However, the comparison group could better regulate their states. Heart rate was significantly high and remained unchanged in the PVE group but decreased in the control group. Alterations during the habituation paradigm in PVE infants could be early indicators of neuropsychological risk impairment. Scope of early habituation assessment is discussed.

Machine Learning-Based Automatic Classification of Video Recorded Neonatal Manipulations and Associated Physiological Parameters: A Feasibility Study

Our objective in this study was to determine if machine learning (ML) can automatically recognize neonatal manipulations, along with associated changes in physiological parameters. A retrospective observational study was carried out in two Neonatal Intensive Care Units (NICUs) between December 2019 to April 2020. Both the video and physiological data (heart rate (HR) and oxygen saturation (SpO₂)) were captured during NICU hospitalization. The proposed classification of neonatal manipulations was achieved by a deep learning system consisting of an Inception-v3 convolutional neural network (CNN), followed by transfer learning layers of Long Short-Term Memory (LSTM). Physiological signals prior to manipulations (baseline) were compared to during and after manipulations. The validation of the system was done using the leave-one-out strategy with input of 8 s of video exhibiting manipulation activity. Ten neonates were video recorded during an average length of stay of 24.5 days. Each neonate had an average of 528 manipulations during their NICU hospitalization, with the average duration of performing these manipulations varying from 28.9 s for patting, 45.5 s for a diaper change, and 108.9 s for tube feeding. The accuracy of the system was 95% for training and 85% for the validation dataset. In neonates <32 weeks’ gestation, diaper changes were associated with significant changes in HR and SpO₂, and, for neonates ≥32 weeks’ gestation, patting and tube feeding were associated with significant changes in HR. The presented system can classify and document the manipulations with high accuracy. Moreover, the study suggests that manipulations impact physiological parameters.

Correlation Between Heart Rate Characteristic Index Score and Severity of Brain Injury in Neonates With Hypoxic-Ischemic Encephalopathy

BACKGROUND

Hypoxic-ischemic encephalopathy (HIE) remains devastating for neonates despite widespread treatment with therapeutic hypothermia (TH). The heart rate characteristic (HRC) index score, a measure of heart rate variability, could prove useful in the management of neonates with HIE as new therapies emerge or when withdrawal-of-support decisions are being considered.

PURPOSE

The main purpose was to describe correlation between HRC index scores and brain magnetic resonance imaging (MRI) severity of injury for neonates with HIE.

METHODS/ANALYSIS

Low/high HRC index scores retrieved at initiation of TH (baseline), 24, 48, 72, and 96 hours, brain MRI severity of injury, and National Institute of Child Health and Human Development Death/Disability and Death scores were collected and analyzed retrospectively. Independent t tests and linear regression were used to examine relationships for each outcome measure.

RESULTS

Twenty-seven neonates were stratified into 2 groups: noninjury (n = 11) and injury (n = 16). Statistically significant relationships were observed. Strikingly, mean low HRC index score for the noninjury group ranged between 0.37 and 0.65 and was between 0.61 and 0.86 for the injury group. Mean high HRC index score for the noninjury group ranged between 0.66 and 1.02 and was between 1.04 and 1.41 for the injury group.

IMPLICATIONS FOR PRACTICE

HRC index score may be a useful guide in the future management of neonates with HIE.

IMPLICATIONS FOR RESEARCH

This study established correlations between HRC index and MRI injury scores in neonates treated with TH. Further research is warranted to establish important relationships between brain injury and HRC index scores before this tool can be used clinically for this purpose.

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.

Trajectories of the heart rate characteristics index, a physiomarker of sepsis in premature infants, predict Neonatal ICU mortality

OBJECTIVE

Trajectories of physiomarkers over time can be useful to define phenotypes of disease progression and as predictors of clinical outcomes. The aim of this study was to identify phenotypes of the time course of late-onset sepsis in premature infants in Neonatal Intensive Care Units.

METHODS

We examined the trajectories of a validated continuous physiomarker, abnormal heart rate characteristics, using functional data analysis and clustering techniques.

PARTICIPANTS

We analyzed continuous heart rate characteristics data from 2989 very low birth weight infants (<1500 grams) from nine NICUs from 2004-2010.

RESULT

Despite the relative homogeneity of the patients, we found extreme variability in the physiomarker trajectories. We identified phenotypes that were indicative of seven and 30 day mortality beyond that predicted by individual heart rate characteristics values or baseline demographic information.

CONCLUSION

Time courses of a heart rate characteristics physiomarker reveal snapshots of illness patterns, some of which were more deadly than others.

Short- and Long-Term Neurodevelopmental Outcomes of Very Preterm Infants with Neonatal Sepsis: A Systematic Review and Meta-Analysis

Sepsis is commonly experienced by infants born very preterm (<32 weeks gestational age and/or <1500 g birthweight), but the long-term functional outcomes are unclear. The objective of this systematic review was to identify observational studies comparing neurodevelopmental outcomes in very preterm infants who had blood culture-proven neonatal sepsis with those without sepsis. Twenty-four studies were identified, of which 19 used prespecified definitions of neurodevelopmental impairment and five reported neurodevelopmental outcomes as continuous variables. Meta-analysis was conducted using 14 studies with defined neurodevelopmental impairment and demonstrated that very preterm infants with neonatal sepsis were at higher risk of impairments, such as cerebral palsy and neurosensory deficits, compared with infants without sepsis (OR 3.18; 95% CI 2.29–4.41). Substantial heterogeneity existed across the studies (I² = 83.1, 95% CI 73–89). The five studies that reported outcomes as continuous variables showed no significant difference in cognitive performance between sepsis and non-sepsis groups. Neonatal sepsis in very preterm infants is associated with increased risk of neurodevelopmental disability. Due to the paucity of longitudinal follow-up data beyond 36 months, the long-term cognitive effect of neonatal sepsis in very preterm infants could not be conclusively determined. Effects on the development of minor impairment could not be assessed, due to the small numbers of infants included in the studies.

Heart rate fluctuation after birth predicts subsequent cardiorespiratory stability in preterm infants

BACKGROUND

Cardiorespiratory stability of preterm infants is a prerequisite for discharge from the neonatal intensive care unit (NICU) but very difficult to predict. We aimed to assess whether characterizing heart rate fluctuation (HRF) within the first days of life has prognostic utility.

METHODS

We conducted a prospective cohort study in 90 preterm infants using a previously validated surface diaphragmatic electromyography (sEMG) method to derive interbeat intervals. We characterized HRF by time series parameters including sample entropy (SampEn) and scaling exponent alpha (ScalExp) obtained from daily 3-h measurements. Data were analyzed by multivariable, multilevel linear regression.

RESULTS

We obtained acceptable raw data from 309/330 sEMG measurements in 76/90 infants born at a mean (range) of 30.2 (24.7-34.0) weeks gestation. We found a significant negative association of SampEn with duration of respiratory support (R² = 0.53, p < 0.001) and corrected age at discontinuation of caffeine therapy (R² = 0.35, p < 0.001) after adjusting for sex, gestational age, birth weight z-score, and sepsis.

CONCLUSIONS

Baseline SampEn calculated over the first 5 days of life carries prognostic utility for an estimation of subsequent respiratory support and pre-discharge cardiorespiratory stability in preterm infants, both important for planning of treatment and utilization of health care resources.

Influence of nasal CPAP on cardiorespiratory control in healthy neonate

The present study aimed to further unravel the effects of nasal continuous positive airway pressure (nCPAP) on the cardiovascular and respiratory systems in the neonatal period. Six-hour polysomnographic recordings were first performed in seven healthy newborn lambs, aged 2-3 days, without and with nCPAP application at 6 cmH₂O (nCPAP-6), in randomized order. The effects of nCPAP-6 on heart rate variability, respiratory rate variability, and cardiorespiratory interrelations were analyzed using a semiautomatic signal processing approach applied to ECG and respiration recordings. Thereafter, a cardiorespiratory mathematical model was adapted to the experimental conditions to gain further physiological interpretation and to simulate higher nCPAP levels (8 and 10 cmH₂O). Results from the signal processing approach suggest that nCPAP-6 applied in newborns with healthy lungs: 1) increases heart rate and decreases the time and frequency domain indices of heart rate variability, especially those representing parasympathetic activity, while increasing the complexity of the RR-interval time series; 2) prolongs the respiratory cycle and expiration duration and decreases respiratory rate variability; and 3) slightly impairs cardiorespiratory interrelations. Model-based analysis revealed that nCPAP-6 increases the heart rate and decreases respiratory sinus arrhythmia amplitude, in association with a reduced parasympathetic efferent activity. These results were accentuated when simulating an increased CPAP level. Overall, our results provide a further understanding of the effects of nCPAP in neonates, in the absence of lung disease.NEW & NOTEWORTHY Application of nasal continuous positive airway pressure (CPAP) at 6 cmH₂O, a level very frequently used in newborns, alters heart and respiratory rate variability, as well as cardiorespiratory interrelations in a full-term newborn model without lung disease. Moreover, whereas nasal CPAP at 6 cmH₂O decreases parasympathetic efferent activity, there is no change in sympathetic efferent activity.

Autonomic Dysfunction in Neonates with Hypoxic Ischemic Encephalopathy Undergoing Therapeutic Hypothermia Impairs Physiological Responses to Routine Care Events

OBJECTIVE

To evaluate whether infants with hypoxic-ischemic encephalopathy and evidence of autonomic dysfunction have aberrant physiological responses to care events that could contribute to evolving brain injury.

STUDY DESIGN

Continuous tracings of heart rate (HR), blood pressure (BP), cerebral near infrared spectroscopy, and video electroencephalogram data were recorded from newborn infants with hypoxic-ischemic encephalopathy who were treated with hypothermia. Videos between 16 and 24 hours of age identified 99 distinct care events, including stimulating events (diaper changes, painful procedures), and vagal stimuli (endotracheal tube manipulations, pupil examinations). Pre-event HR variability was used to stratify patients into groups with impaired versus intact autonomic nervous system (ANS) function. Postevent physiological responses were compared between groups with the nearest mean classification approach.

RESULTS

Infants with intact ANS had increases in HR/BP after stimulating events, whereas those with impaired ANS showed no change or decreased HR/BP. With vagal stimuli, the HR decreased in infants with intact ANS but changed minimally in those with impaired ANS. A pupil examination in infants with an intact ANS led to a stable or increased BP, whereas the BP decreased in the group with an impaired ANS. Near infrared spectroscopy measures of cerebral blood flow/blood volume increased after diaper changes in infants with an impaired ANS, but were stable or decreased in those with an intact ANS.

CONCLUSION

HR variability metrics identified infants with impaired ANS function at risk for maladaptive responses to care events. These data support the potential use of HR variability as a real-time, continuous physiological biomarker to guide neuroprotective care in high-risk newborns.

Efficient Fetal-Maternal ECG Signal Separation from Two Channel Maternal Abdominal ECG via Diffusion-Based Channel Selection

There is a need for affordable, widely deployable maternal-fetal ECG monitors to improve maternal and fetal health during pregnancy and delivery. Based on the diffusion-based channel selection, here we present the mathematical formalism and clinical validation of an algorithm capable of accurate separation of maternal and fetal ECG from a two channel signal acquired over maternal abdomen. The proposed algorithm is the first algorithm, to the best of the authors' knowledge, focusing on the fetal ECG analysis based on two channel maternal abdominal ECG signal, and we apply it to two publicly available databases, the PhysioNet non-invasive fECG database (adfecgdb) and the 2013 PhysioNet/Computing in Cardiology Challenge (CinC2013), to validate the algorithm. The state-of-the-art results are achieved when compared with other available algorithms. Particularly, the F₁ score for the R peak detection achieves 99.3% for the adfecgdb and 87.93% for the CinC2013, and the mean absolute error for the estimated R peak locations is 4.53 ms for the adfecgdb and 6.21 ms for the CinC2013. The method has the potential to be applied to other fetal cardiogenic signals, including cardiac doppler signals.

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.

Effect of Temperature on Heart Rate Variability in Neonatal ICU Patients With Hypoxic-Ischemic Encephalopathy

OBJECTIVE

To determine whether measures of heart rate variability are related to changes in temperature during rewarming after therapeutic hypothermia for hypoxic-ischemic encephalopathy.

DESIGN

Prospective observational study.

SETTING

Level 4 neonatal ICU in a free-standing academic children's hospital.

PATIENTS

Forty-four infants with moderate to severe hypoxic-ischemic encephalopathy treated with therapeutic hypothermia.

INTERVENTIONS

Continuous electrocardiogram data from 2 hours prior to rewarming through 2 hours after completion of rewarming (up to 10 hr) were analyzed.

MEASUREMENTS AND MAIN RESULTS

Median beat-to-beat interval and measures of heart rate variability were quantified including beat-to-beat interval SD, low and high frequency relative spectral power, detrended fluctuation analysis short and long α exponents (αS and αL), and root mean square short and long time scales. The relationships between heart rate variability measures and esophageal/axillary temperatures were evaluated. Heart rate variability measures low frequency, αS, and root mean square short and long time scales were negatively associated, whereas αL was positively associated, with temperature (p < 0.01). These findings signify an overall decrease in heart rate variability as temperature increased toward normothermia.

CONCLUSIONS

Measures of heart rate variability are temperature dependent in the range of therapeutic hypothermia to normothermia. Core body temperature needs to be considered when evaluating heart rate variability metrics as potential physiologic biomarkers of illness severity in hypoxic-ischemic encephalopathy infants undergoing therapeutic hypothermia.

Assessment of general movements and heart rate variability in prediction of neurodevelopmental outcome in preterm infants

BACKGROUND

Adverse neurologic outcome in preterm infants could be associated with abnormal heart rate (HR) characteristics as well as with abnormal general movements (GMs) in the 1st month of life.

AIMS

To demonstrate to what extent GMs assessment can predict neurological outcome in preterm infants in our clinical setting; and to assess the clinical usefulness of time-domain indices of heart rate variability (HRV) in improving predictive value of poor repertoire (PR) GMs in writhing period.

STUDY DESIGN

Qualitative assessment of GMs at 1 and 3 months corrected age; 24h electrocardiography (ECG) recordings and analyzing HRV at 1 month corrected age.

SUBJECTS

Seventy nine premature infants at risk of neurodevelopmental impairments were included prospectively.

OUTCOME MEASURES

Neurodevelopmental outcome was assessed at the age of 2 years corrected. Children were classified as having normal neurodevelopmental status, minor neurologic dysfunction (MND), or cerebral palsy (CP).

RESULTS

We found that GMs in writhing period (1 month corrected age) predicted CP at 2 years with sensitivity of 100%, and specificity of 72.1%. Our results demonstrated the excellent predictive value of cramped synchronized (CS) GMs, but not of PR pattern. Analyzing separately a group of infants with PR GMs we found significantly lower values of HRV parameters in infants who later developed CP or MND vs. infants with PR GMs who had normal outcome.

CONCLUSIONS

The quality of GMs was predictive for neurodevelopmental outcome at 2 years. Prediction of PR GMs was significantly enhanced with analyzing HRV parameters.

Heart rate characteristic index monitoring for bloodstream infection in an NICU: a 3-year experience

BACKGROUND

Bloodstream infection (BSI) among neonatal intensive care unit (NICU) infants is a frequent problem associated with poor outcomes. Monitoring for abnormal heart rate characteristics (HRCs) may decrease infant mortality by alerting clinicians to sepsis before it becomes clinically apparent.

METHODS

HRC scores were acquired using the HRC (HeRO) monitor system from Medical Predictive Science Corporation and entered into the electronic medical record by bedside staff. We retrospectively analysed HRC scores recorded twice daily in the medical record during a 30-month period (1 January 2010 through 30 June 2012) for infants in the NICU at the Monroe Carell Jr. Children's Hospital at Vanderbilt. We identified infants that met Centers for Disease Control criteria for late-onset BSI (>3 days of life) during the study period.

RESULTS

During the study period, we recorded 127 673 HRC scores from 2384 infants. We identified 46 infants with BSI. Although 8% (9701/127 673) of the HRC scores were ≥2 and 1% (1387/127 673) were ≥5, BSI (at any time) was observed in just 5% of patients with HRC scores ≥2, and 9% of patients with HRC scores ≥5. Of infants with BSI, 5/46 (11%) had at least one HRC score ≥5 and 17/46 (37%) had at least one score ≥2 recorded in the 48 h period prior to the evaluation that resulted in the first positive blood culture of the episode.

CONCLUSIONS

In our single-centre retrospective study, elevated HRC scores had limited ability to detect BSI. BSI was infrequent at any time during hospitalisation in infants with significantly elevated HRC scores.

Early Heart Rate Characteristics Predict Death and Morbidities in Preterm Infants

OBJECTIVES

To determine whether an early heart rate characteristics (HRC) index (HeRO score), measured in the first day and week after birth predicts death and morbidities compared with established illness severity scores.

STUDY DESIGN

For all very low birth weight infants in a single neonatal intensive care unit from 2004-2014, the average first day HRC index was calculated within 24 hours of birth (aHRC-24h) and the average first week HRC index within 7 days of birth (aHRC-7d). The Score for Neonatal Acute Physiology (SNAP-II) and Clinical Risk Indicator for Babies (CRIB-II) were calculated when data were available. The aHRC was compared with the SNAP-II and CRIB-II for predicting death, late-onset septicemia, necrotizing enterocolitis, bronchopulmonary dysplasia, severe intraventricular hemorrhage, or severe retinopathy of prematurity.

RESULTS

All 4 scores were associated with death and severe intraventricular hemorrhage (P < .01). The OR and 95% CI for every 1-point increase in aHRC for predicting mortality, adjusted for gestational age, was 1.59 (1.25-2.00) for aHRC-24h and 2.61 (1.58-4.33) for aHRC-7d. High aHRC-7d, SNAP-II, and CRIB-II were associated with bronchopulmonary dysplasia (P < .001). High aHRC-7d was associated with late-onset septicemia (P < .05). None of the scores predicted necrotizing enterocolitis or severe retinopathy of prematurity.

CONCLUSIONS

HRC assessed in the first day or first week after birth compares favorably to established risk scores to predict death and morbidities in very low birth weight infants.

Predictive monitoring for sepsis and necrotizing enterocolitis to prevent shock

Despite vigilant clinical assessment of infants in the neonatal intensive care unit (NICU), diagnosis of sepsis and necrotizing enterocolitis often does not occur until an infant has significant hemodynamic compromise. Predictive monitoring involves analysis of vital signs and other clinical data to identify infants at highest risk and to detect early-stage illness, leading to timelier treatment and improved outcomes. The first vital-sign predictive monitoring device developed for sepsis detection in babies in the NICU is the heart rate characteristics index (HeRO) monitor, which continuously analyzes the electrocardiogram signal for low heart rate variability and transient decelerations. Use of this monitor in very low birth weight infants (<1500 g) was shown in a large multicenter randomized clinical trial to significantly reduce mortality. The purpose of this review is (1) to summarize the physiologic changes in neonatal sepsis and progression to shock, (2) to review efforts toward risk stratification for sepsis shortly after birth based on demographic and physiologic scoring systems, (3) to describe development and implementation of heart rate characteristics monitoring and other important aspects of sepsis early warning systems, and (4) to provide an overview of current research analyzing multiple vital signs and other clinical variables in an attempt to develop even more effective predictive monitoring devices and systems.

Heart rate variability evaluation in the assessment and management of in-utero drug-exposed infants

Aim:

To determine whether heart rate variability parameters vary between in-utero drug-exposed infants and controls. To determine correlations between Finnegan score and heart rate variability parameters. To differentiate those drug-exposed infants who require treatment from those infants who do not.

Methods:

A total of 24 jaundiced control subjects and 25 in-utero drug-exposed infants were enrolled. The Finnegan score and an electrocardiographic rhythm strip were obtained at 4-h intervals. RR intervals (time between consecutive R waves) were manually tabulated from the rhythm strip and analyzed. Time-domain heart rate variability parameters were calculated and analyzed for both groups.

Results:

Heart rate variability parameters were cumulatively lower over 3 days in in-utero drug-exposed infants compared with controls (p < 0.05). Root mean square of differences of standard deviation of RR intervals on first day of life, and standard deviation of RR intervals, percentage of consecutive RR intervals greater than 50 ms, and root mean square of differences of standard deviation of RR intervals on the second day of life were significantly lower between in-utero drug-exposed infants and control infants. Three out of five parameters were significantly lower in in-utero drug-exposed infants pre-treatment versus post-treatment (p = 0.001, p = 0.0001, and p = 0.021, respectively). Root mean square of differences of standard deviation of RR intervals was able to differentiate in-utero drug-exposed infants requiring opiate therapy and in-utero drug-exposed infants that did not (p = 0.02).

Conclusion:

Heart rate variability analysis can contribute to the management of in-utero drug-exposed infants. Heart rate variability could be used in dose titration.