114 - Heart Rate and Brain Injury in Infants with Hypoxic Ischemic Encephalopathy

Poster Number: 114
Publication Number: 114.1976

Background: Newborn infants with hypoxic ischemic encephalopathy (HIE) are at increased risk for death, brain injury and neurodevelopmental impairment (NDI). Despite improvements in adverse outcomes with therapeutic hypothermia (TH), 45-55% will nonetheless develop brain injury. Identifying susceptible infants remains challenging. Bradycardia frequently manifests within the framework of the "diving reflex", a mechanism linked to fetal hypoxia, and represents a significant hemodynamic consequence of TH.

Objective: Our aim was to examine the association between bradycardia following TH initiation in infants with HIE, and adverse outcomes. We hypothesized that infants with more severe injury will display autonomic dysfunction and therefore be less effective in using the diving reflex.

Design/Methods: A retrospective study of infants born at >35weeks gestational age (GA) between the years 2012-2022 and admitted to a single center neonatal intensive care unit (NICU). Electronic medical records were searched for any relevant diagnosis: HIE, neonatal encephalopathy, resuscitation, low APGAR score and/or TH. Infants were divided into 3 groups by encephalopathy severity; moderate-severe HIE, mild HIE or controls (no HIE). Heart rate (HR) was recorded for each infant every minute from time of admission for five consecutive days or discharge. An adverse outcome was defined as mortality, NDI at follow-up or brain injury on magnetic resonance imaging.

Results: 1202 infant medical records were reviewed, of which 726 were included (Figure1). Demographic data are presented in Table 1. The median number of HR values per infant differed by group (7050 [6966-7068] vs 5231 [3508-6997] vs 4502 [2210-7002] for infants with moderate-severe HIE, mild HIE and controls, respectively. p< 0.001). Outcome ascertainment was available for 357 (49%) infants. HR trends were stable over time and similar in infants with mild HIE compared to controls (Figure2A). Infants with moderate-severe HIE had a complex trend, with large variation in the first two days of life, relative bradycardia during the third day and an increase in HR after rewarming (days 4-5). Infants with an adverse outcome had higher HR values during the first two days of life, despite TH (Figure2B).

Conclusion(s): HR trends were associated with adverse outcomes in infants undergoing TH for moderate-severe HIE. Whether HR monitoring could assist in identifying infants at the highest risk of adverse outcomes warrants further investigation. HR analysis could prove to be a promising predictive tool in guiding the application of neuroprotective strategies.