Abstract
BackgroundInfants with mild HIE are at risk of significant disability at follow-up. In the pre-therapeutic hypothermia (TH) era, electroencephalography (EEG) within 6 hours of birth was most predictive of outcome. This study aims to identify and describe features of early EEG and heart rate variability (HRV) (<6 hours of age) in infants with mild HIE compared to healthy term infants.MethodsInfants >36 weeks with mild HIE, not undergoing TH, with EEG before 6 hours of age were identified from 4 prospective cohort studies conducted in the Cork University Maternity Services, Ireland (2003–2019). Control infants were taken from a contemporaneous study examining brain activity in healthy term infants. EEGs were qualitatively analysed by two neonatal neurophysiologists and quantitatively assessed using multiple features of amplitude, spectral shape and inter-hemispheric connectivity. Quantitative features of HRV were assessed in both the groups.ResultsFifty-eight infants with mild HIE and sixteen healthy term infants were included. Seventy-two percent of infants with mild HIE had at least one abnormal EEG feature on qualitative analysis and quantitative EEG analysis revealed significant differences in spectral features between the two groups. HRV analysis did not differentiate between the groups.ConclusionsQualitative and quantitative analysis of the EEG before 6 hours of age identified abnormal EEG features in mild HIE, which could aid in the objective identification of cases for future TH trials in mild HIE.ImpactInfants with mild HIE currently do not meet selection criteria for TH yet may be at risk of significant disability at follow-up.In the pre-TH era, EEG within 6 hours of birth was most predictive of outcome; however, TH has delayed this predictive value.72% of infants with mild HIE had at least one abnormal EEG feature in the first 6 hours on qualitative assessment.Quantitative EEG analysis revealed significant differences in spectral features between infants with mild HIE and healthy term infants.Quantitative EEG features may aid in the objective identification of cases for future TH trials in mild HIE.
Highlights
Hypoxic–ischaemic encephalopathy (HIE) accounts for 1–3 per 1000 live births per year[1] and is the leading cause of acquired brain injury in term infants
We have found significant differences between the EEG features of infants with mild HIE and healthy term infants
Our qualitative analysis identified the presence of specific abnormal EEG features in the HIE group
Summary
Hypoxic–ischaemic encephalopathy (HIE) accounts for 1–3 per 1000 live births per year[1] and is the leading cause of acquired brain injury in term infants. Therapeutic hypothermia (TH) has become standard of care for infants with moderate-to-severe HIE.[6] To be effective, TH must be commenced early, within 6 hours of birth.[7,8,9] it can often be difficult to differentiate clinically between mild and moderate encephalopathy in this short timeframe.[10,11] TH is not currently indicated for infants with mild HIE These infants were considered to have normal outcomes[2,12,13] and so were omitted from TH trials due to the perceived low risk of disability. CONCLUSIONS: Qualitative and quantitative analysis of the EEG before 6 hours of age identified abnormal EEG features in mild HIE, which could aid in the objective identification of cases for future TH trials in mild HIE
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