Development of a Heart Rate Variability Risk Score to Predict Organ Dysfunction and Death in Critically Ill Children

Derivation, Validation, and Clinical Relevance of a Pediatric Sepsis Phenotype With Persistent Hypoxemia, Encephalopathy, and Shock

OBJECTIVES

Untangling the heterogeneity of sepsis in children and identifying clinically relevant phenotypes could lead to the development of targeted therapies. Our aim was to analyze the organ dysfunction trajectories of children with sepsis-associated multiple organ dysfunction syndrome (MODS) to identify reproducible and clinically relevant sepsis phenotypes and determine if they are associated with heterogeneity of treatment effect (HTE) to common therapies.

DESIGN

Multicenter observational cohort study.

SETTING

Thirteen PICUs in the United States.

PATIENTS

Patients admitted with suspected infections to the PICU between 2012 and 2018.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We used subgraph-augmented nonnegative matrix factorization to identify candidate trajectory-based phenotypes based on the type, severity, and progression of organ dysfunction in the first 72 hours. We analyzed the candidate phenotypes to determine reproducibility as well as prognostic, therapeutic, and biological relevance. Overall, 38,732 children had suspected infection, of which 15,246 (39.4%) had sepsis-associated MODS with an in-hospital mortality of 10.1%. We identified an organ dysfunction trajectory-based phenotype (which we termed persistent hypoxemia, encephalopathy, and shock) that was highly reproducible, had features of systemic inflammation and coagulopathy, and was independently associated with higher mortality. In a propensity score-matched analysis, patients with persistent hypoxemia, encephalopathy, and shock phenotype appeared to have HTE and benefit from adjuvant therapy with hydrocortisone and albumin. When compared with other high-risk clinical syndromes, the persistent hypoxemia, encephalopathy, and shock phenotype only overlapped with 50%-60% of patients with septic shock, moderate-to-severe pediatric acute respiratory distress syndrome, or those in the top tier of organ dysfunction burden, suggesting that it represents a nonsynonymous clinical phenotype of sepsis-associated MODS.

CONCLUSIONS

We derived and validated the persistent hypoxemia, encephalopathy, and shock phenotype, which is highly reproducible, clinically relevant, and associated with HTE to common adjuvant therapies in children with sepsis.

Promoting Functional Recovery in Critically Ill Children

Over two-thirds of pediatric critical illness survivors will experience functional impairments that persist after discharge, that is, post-intensive care syndrome in pediatrics (PICS-p). Risk factors include child and family characteristics, invasive procedures, and social determinants of health. Approaches to remediate PICS-p include early rehabilitation, minimizing sedation, psychosocial resources for caregivers, delivery of family-centered care, and longitudinal screening for PICS-p. Challenges include feasible and validated approaches to screening, and resources and coordination for multidisciplinary care. Next steps should include resources to identify and address adverse social determinants of health and examination of treatment efficacy and implementation equity.

Pediatric Critical Care in the Twenty-first Century and Beyond

Pediatric critical care addresses prevention, diagnosis, and treatment of organ dysfunction in the setting of increasingly complex patients, therapies, and environments. Soon burgeoning data science will enable all aspects of intensive care: driving facilitated diagnostics, empowering a learning health-care environment, promoting continuous advancement of care, and informing the continuum of critical care outside the intensive care unit preceding and following critical illness/injury. Although novel technology will progressively objectify personalized critical care, humanism, practiced at the bedside, defines the essence of pediatric critical care now and in the future.

Heart Rate Variability in Children with Moderate and Severe Traumatic Brain Injury: A Prospective Observational Study

The aim of this study was to assess the feasibility of continuous monitoring of heart rate variability (HRV) in children with traumatic brain injury (TBI) hospitalized in a pediatric intensive care unit (PICU) and collect preliminary data on the association between HRV, neurological outcome, and complications. This is a prospective observational cohort study in a tertiary academic PICU. Children admitted to the PICU ≤24 hours after moderate or severe TBI were included in the study. Children suspected of being brain dead at PICU entry or with a pacemaker were excluded. Children underwent continuous monitoring of electrocardiographic (ECG) waveforms over 7 days post-TBI. HRV analysis was performed retrospectively, using a standardized, validated HRV analysis software (CIMVA). The occurrence of medical complications (“event”: intracranial hypertension, cerebral hypoperfusion, seizure, and cardiac arrest) was prospectively documented. Outcome of children 6 months post-TBI was assessed using the Glasgow Outcome Scale – Extended Pediatric (GOS-E Peds). Fifteen patients were included over a 20-month period. Thirteen patients had ECG recordings available and 4 had >20% of missing ECG data. When ECG was available, HRV calculation was feasible (average 88%; range 70–97%). Significant decrease in overall HRV coefficient of variation and Poincaré SD2 (p < 0.05) at 6 hours post–PICU admission was associated with an unfavorable outcome (defined as GOS-E Peds ≥ 3, or a deterioration of ≥2 points over baseline score). Several HRV metrics exhibited significant and nonsignificant variation in HRV during event. This study demonstrates that it is feasible to monitor HRV in the PICU provided ECG data are available; however, missing ECG data are not uncommon. These preliminary data suggest that altered HRV is associated with unfavorable neurological outcome and in-hospital medical complications. Larger prospective studies are needed to confirm these findings and to explore if HRV offers reliable and clinically useful prediction data that may help clinical decision making.

Heart rate variability is associated with encephalopathy and outcomes in pediatric acute liver failure

BACKGROUND

More than half of children with pediatric acute liver failure (PALF) experience hepatic encephalopathy (HE), which is related to poor outcomes; however, HE is difficult to diagnose in children. The objective of this study was to evaluate if heart rate variability (HRV), a continuous measure of autonomic nervous system function, was related to the presence and severity of HE as well as clinical outcomes in children with PALF.

METHODS

We conducted a retrospective observational cohort study of 38 critically ill children with PALF to examine the association between HRV and HE severity and clinical outcome. HRV was estimated using the integer HRV (HRVi). Categorical variables were compared using the Fisher Exact test and continuous variables were compared using Kruskal-Wallis tests. Associations between grades of HE and minimum and median HRVi were evaluated with Pearson's correlation, with p values <0.05 considered significant.

RESULTS

A more negative median and minimum HRVi, indicating poorer autonomic nervous system function, was significantly associated with abnormal EEG findings, presence of HE, and poor outcomes (death or listing for transplant).

CONCLUSIONS

Heart rate variability may hold promise to predict outcomes in children with PALF, but these findings should be replicated in a larger sample.

IMPACT

The findings of our study suggest that heart rate variability is associated with clinical outcomes in children with acute liver failure, a cohort for which prognostics are challenging, especially in young children and infants. Use of heart rate variability in the clinical setting may facilitate earlier detection of children with pediatric acute liver failure (PALF) at high risk for severe hepatic encephalopathy and poor outcomes. Identification of children with PALF at high risk of decompensation may assist clinicians in making decisions about liver transplantation, an important, but resource-limited, treatment of PALF.

Association Between Heart Rate Variability and Inflammatory Biomarkers in Critically Ill Children

OBJECTIVES

The autonomic nervous system (ANS) can both modulate and be modulated by the inflammatory response during critical illness. We aimed to determine whether heart rate variability (HRV), a measure of ANS function, is associated with proinflammatory biomarker levels in critically ill children.

DESIGN

Two cohorts were analyzed. The first was a prospective observational cohort from August 2018 to August 2020 who had plasma proinflammatory cytokine measurements within 72 hours of admission, including tumor necrosis factor-α, interleukin (IL)-1β, IL-6, and IL-8. The second was a retrospective cohort from June 2012 to August 2020 who had at least one C-reactive protein (CRP) measurement within 72 hours of admission.

SETTING

Forty-six-bed PICU.

PATIENTS

Critically ill children in either cohort who had continuous heart rate data available from the bedside monitors.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Sixty-two patients were included in the prospective cohort and 599 patients in the retrospective cohort. HRV was measured using the age-adjusted integer heart rate variability (HRVi), which is the sd of the heart rate sampled every 1 second over 5 consecutive minutes. The median HRVi was measured in the 12-hour period ending 30 minutes prior to inflammatory biomarker collection. HRVi was inversely correlated with IL-6, IL-8, and CRP levels (p ≤ 0.02); correlation with IL-8 and CRP persisted after adjusting for Pediatric Risk of Mortality III and age, and median HR and age (p < 0.001).

CONCLUSIONS

HRVi is inversely correlated with IL-6, IL-8, and CRP. Further studies are needed to validate this measure as a proxy for a proinflammatory state.

Virtual Reality in the Pediatric Intensive Care Unit: Patient Emotional and Physiologic Responses

Context

Patients in the Pediatric Intensive Care Unit (PICU) are limited in their ability to engage in developmentally typical activity. Long-term hospitalization, especially with minimal interpersonal engagement, is associated with risk for delirium and delayed recovery. Virtual reality (VR) has growing evidence as a safe, efficacious, and acceptable intervention for pain and distress management in the context of uncomfortable healthcare procedures, and for enhancing engagement in, and improving outcomes of rehabilitation therapy.

Hypothesis

Critically ill children may experience high levels of engagement and physiologic effects while engaging with VR.

Methods and Models

This cross-sectional study of 3–17-year-old children admitted to a PICU used a VR headset to deliver 360-degree immersive experiences. This study had a mixed-method approach, including standardized behavioral coding, participant and parent surveys, and participant physiologic responses. Investigators noted comments the child made about VR, observed emotional responses, and documented an engagement score. To determine physiologic response to VR, integer heart rate variability (HRVi) was collected 30 min before, during, and 30 min after VR.

Results

One hundred fifteen participants were enrolled from 6/18 to 10/19, and they interacted with VR for a median of 10 min (interquartile range 7–17). Most children enjoyed the experience; 83% of participants smiled and 36% laughed while using VR. Seventy-two percent made positive comments while using VR. The strongest age-related pattern regarding comments was that the youngest children were more likely to share the experience with others. Seventy-nine percent of participants were highly engaged with VR. Ninety-two percent of parents reported that VR calmed their child, and 78% of participants felt that VR was calming. HRVi Minimum scores were significantly higher during VR than pre- (p < 0.001) or post-VR (p < 0.001). There was no significant difference between pre-and post-VR (p = 0.387); therefore, children returned to their pre-intervention state following VR.

Interpretations and Conclusions

Children admitted to the PICU are highly engaged with and consistently enjoyed using VR. Both participants and parents found VR to be calming, consistent with intra-intervention physiologic improvements in HRVi. VR is an immersive tool that can augment the hospital environment for children.

Discovery of signatures of fatal neonatal illness in vital signs using highly comparative time-series analysis

To seek new signatures of illness in heart rate and oxygen saturation vital signs from Neonatal Intensive Care Unit (NICU) patients, we implemented highly comparative time-series analysis to discover features of all-cause mortality in the next 7 days. We collected 0.5 Hz heart rate and oxygen saturation vital signs of infants in the University of Virginia NICU from 2009 to 2019. We applied 4998 algorithmic operations from 11 mathematical families to random daily 10 min segments from 5957 NICU infants, 205 of whom died. We clustered the results and selected a representative from each, and examined multivariable logistic regression models. 3555 operations were usable; 20 cluster medoids held more than 81% of the information, and a multivariable model had AUC 0.83. New algorithms outperformed others: moving threshold, successive increases, surprise, and random walk. We computed provenance of the computations and constructed a software library with links to the data. We conclude that highly comparative time-series analysis revealed new vital sign measures to identify NICU patients at the highest risk of death in the next week.

Autonomic Nervous System Dysfunction Is Associated With Re-hospitalization in Pediatric Septic Shock Survivors

Objective: Re-hospitalization after sepsis can lead to impaired quality of life. Predictors of re-hospitalization could help identify sepsis survivors who may benefit from targeted interventions. Our goal was to determine whether low heart rate variability (HRV), a measure of autonomic nervous system dysfunction, is associated with re-hospitalization in pediatric septic shock survivors. Materials and Methods: This was a retrospective, observational cohort study of patients admitted between 6/2012 and 10/2020 at a single institution. Patients admitted to the pediatric intensive care unit with septic shock who had continuous heart rate data available from the bedside monitors and survived their hospitalization were included. HRV was measured using age-normalized z-scores of the integer HRV (HRVi), which is the standard deviation of the heart rate sampled every 1 s over 5 consecutive minutes. The 24-h median HRVi was assessed on two different days: the last 24 h of PICU admission ("last HRVi") and the 24-h period with the lowest median HRVi ("lowest HRVi"). The change between the lowest and last HRVi was termed "delta HRVi." The primary outcome was re-hospitalization within 1 year of discharge, including both emergency department encounters and hospital readmission, with sensitivity analyses at 30 and 90 days. Kruskal-Wallis, logistic regression, and Poisson regression evaluated the association between HRVi and re-hospitalizations and adjusted for potential confounders. Results: Of the 463 patients who met inclusion criteria, 306 (66%) were re-hospitalized, including 270 readmissions (58%). The last HRVi was significantly lower among re-hospitalized patients compared to those who were not (p = 0.02). There was no difference in the lowest HRVi, but patients who were re-hospitalized showed a smaller recovery in their delta HRVi compared to those who were not re-hospitalized (p = 0.02). This association remained significant after adjusting for potential confounders. In the sensitivity analysis, a smaller recovery in delta HRVi was consistently associated with a higher likelihood of re-hospitalization. Conclusion: In pediatric septic shock survivors, a smaller recovery in HRV during the index admission is significantly associated with re-hospitalization. This continuous physiologic measure could potentially be used as a predictor of patients at risk for re-hospitalization and lower health-related quality of life.