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A Piglet Model of Neonatal Hypoxic-Ischemic Encephalopathy
Published on: May 16, 2015
Autonomic Dysfunction in Neonates with Hypoxic Ischemic Encephalopathy Undergoing Therapeutic Hypothermia Impairs
Heather Campbell1, Rathinaswamy B Govindan2, Srinivas Kota3
1Pediatric Residency Program, Children's National Health System, Washington, DC.
Insights
Infants with impaired autonomic nervous systems (ANS) show abnormal physiological responses to routine care, indicating a risk for brain injury. Heart rate variability can identify these high-risk newborns for tailored neuroprotective strategies.
Area of Science:
- Neonatal neurology
- Autonomic nervous system function
- Physiological monitoring
Background:
- Hypoxic-ischemic encephalopathy (HIE) is a major cause of neonatal brain injury.
- Autonomic dysfunction is common in HIE infants and may exacerbate brain injury.
- Caregiving events can trigger physiological stress in vulnerable newborns.
Purpose of the Study:
- To determine if infants with HIE and autonomic dysfunction exhibit aberrant physiological responses to care events.
- To assess if these aberrant responses contribute to ongoing brain injury.
- To explore the utility of heart rate variability (HRV) in identifying such infants.
Main Methods:
- Continuous monitoring of heart rate (HR), blood pressure (BP), cerebral near-infrared spectroscopy (NIRS), and video electroencephalogram (EEG) in HIE infants treated with hypothermia.
- Identification of 99 care events (stimulating and vagal) between 16-24 hours of age.
- Stratification of infants into impaired vs. intact autonomic nervous system (ANS) groups based on pre-event HRV.
Main Results:
- Infants with intact ANS showed expected HR/BP increases to stimuli, while impaired ANS infants had blunted responses.
- Vagal stimuli caused HR decrease in intact ANS infants, but minimal change in impaired ANS infants.
- Cerebral blood flow/volume increased in impaired ANS infants during diaper changes, unlike intact ANS infants.
Conclusions:
- HRV metrics effectively identify HIE infants with impaired ANS function at risk for maladaptive responses to care.
- These findings support HRV as a real-time biomarker for guiding neuroprotective care in high-risk newborns.
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.
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