Abstracts

Rationale: Background : Hypoxic ischemic encephalopathy (HIE) is a common problem in term neonates. Predicting long term outcomes are important for medical decision making and family planning. Brain MRI and conventional EEG are widely used to assess the severity of brain injury. EEG background rating systems typically require recognition of multiple neonatal EEG features and therefore may require more experience interpreting neonatal EEG. We developed a simplified rating scale using continuity and state changes that correlated with brain injury by MRI in a pilot study of 50 newborns with HIE. However interrater agreement has not been established. Objective: To determine the interrater reliability of a simplified EEG background rating scale as a prognostic factor in term neonates with HIE treated with hypothermia. Methods: Methods: We retrospectively reviewed conventional continuous EEG in hypothermia infants with HIE during the initial EEG (first 24 hours of life), 24-36 hours of life and 60-72 hours of life. The EEG background was categorized into six patterns:1-Continuous with or without state change, 2-Discontinuous activity occupying 50% or less of the first hour, 3-Discontinuous more than 50% of the first hour with state change, 4-Discontinuous more than 50% of the first hour without state change, 5-low voltage suppression or burst suppression or inactive, 6- background can't be assessed due to status epilepticus. An alternate scale using more traditional neonatal EEG characterization was also utilized:1-Continuous with or without state change, 2-Discontinuous normal for age with or without state change, 3-Excessively discontinuous with state change, 4- Excessively discontinuous without state change, 5-low voltage suppression or burst suppression or inactive, 6- background can't be assessed due to status epilepticus. EEG background continuity/amplitude was rated in the first hour of each recording. State changes were rated for the first three hours of each segment. If the background pattern changed more than one category by the end of the segment, a new rating was given. Two EEG raters, blinded to clinical history and outcome, independently rated the EEGs. One rater is an expert neonatal neurophysiologist and the other is a neurophysiologist with intermediate experience in neonatal eeg interpretation. Interrater agreement was analyzed using percent of agreement and Kappa Statistic (k). Kappa values of < 0.2 were considered poor, 0.2-0.4 fair, 0.41-0.6 moderate, 0.61-0.8 substantial, and >0.8 near perfect agreement. Results: Result: We studied 20 neonates who underwent therapeutic hypothermia. The average gestational age was 38 wks (range between 34 ?" 43 wks),birth weight was 3.453 635 g. The EEG start times were between 4- 21 hours of life (median 11.6 hours). Of the 56 records interpretable for these features, the percent of agreement is 67.9% with moderate kappa (?= 0.593, p=0.00). Interrater agreement for background state change (n=54) is also moderate (?= 0.519, p=0.00). The percent of agreement between two raters is 77.8 %. The alternate EEG background (n=56) had similar reliability, with percent of agreement 69.6% (?= 0.617, p=0.00). Conclusions: Conclusion: Interrater reliability for a novel simplified scale utilizing EEG background and state change is moderately reliable and comparable to commonly used alternative background rating terminology. This study supports the reliability of this rating scale. Further work is ongoing to establish its validity in predicting neurological outcomes in newborns with HIE. Funding: none