Autonomic Function in Babies with Hypoxic-Ischemic Encephalopathy (HIE)

Hypoxic-ischemic encephalopathy (HIE) is a type of birth injury stemming from oxygen deprivation during or around the time of birth. Babies with HIE have brain damage which often results in permanent health conditions and disabilities such as cerebral palsy.

Although brain imaging and other diagnostic techniques can help medical professionals estimate the extent of damage, it would be very helpful to have a real-time biomarker that could help physicians know when to provide even more extensive neuroprotective care. New research indicates that signs of autonomic dysfunction during routine care could provide valuable information about a baby’s overall well-being.

What is autonomic dysfunction?

“Autonomic dysfunction” occurs when behaviors associated with the autonomic nervous system (ANS) appear abnormal. The ANS controls unconscious functions such as breathing and digestion.

How can autonomic dysfunction be recognized?

Signs of autonomic dysfunction can be recognized during routine care and monitoring. Campbell et al. (2018) recently published the results of a study on 25 infants being treated for HIE with therapeutic hypothermia. The data they used included continuous heart rate tracings, blood pressure readings, cerebral near infrared spectroscopy (which measures oxygen levels in brain tissue), and video electroencephalogram. The researchers analyzed how these measurements change in response to care events such as pupil examinations, changing a diaper, and manipulating an endotracheal tube.

Campbell et al. then used heart rate variability (fewer fluctuations are thought to indicate dysfunctional ANS) and non-invasive brain MRI to determine the extent of damage. They compared these findings with the infants’ physiological responses to the aforementioned care activities.

The researchers found that infants with impaired ANS (i.e. less heart rate variability) prior to a care event responded differently than infants with functional ANS. Diaper changes and other stimulating interventions decreased heart rate and blood pressure in babies with impaired ANS, but increased heart rate in babies with intact ANS. Babies with impaired ANS had no change in heart rate and a decrease in blood pressure after a pupil exam, while babies with intact ANS had an expected decrease in heart rate and no change in blood pressure. Breathing tube manipulations led to similar responses, although the ANS impaired group showed a slight increase in heart rate a few minutes later (1).

An Massaro, one of the authors of this paper, noted that the predictive value of autonomic function markers such as those used in this research means that, “we may be able to offer new hope for infants with HIE” (2).

Other recent blog posts on birth injuries and neonatal health

Sources

  1. Campbell, H., Govindan, R. B., Kota, S., Al-Shargabi, T., Metzler, M., Andescavage, N., … & Massaro, A. N. (2018). Autonomic Dysfunction in Neonates with Hypoxic Ischemic Encephalopathy Undergoing Therapeutic Hypothermia Impairs Physiological Responses to Routine Care Events. The Journal of Pediatrics, 196, 38-44.
  2. Kresge, N. (2018, November 05). Keeping an eye on autonomic function for infants with HIE | Children’s National. Retrieved November 30, 2018, from https://innovationdistrict.childrensnational.org/keeping-an-eye-on-autonomic-function-for-infants-with-hie/

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