Abstracts

Rationale: Therapeutic hypothermia (TH) has shown to improve survival and neurological development in term neonates with hypoxic-ischemic encephalopathy (HIE). Continuous Video-Electroencephalography (CVEEG) is used to monitor seizures in HIE and predictneurodevelopmental outcome. CVEEG is an expensive procedure (approximately $2000 per 24h). Application of scalp EEG electrodes continuously during TH can limit access to neuroimaging and can be associated with skin lesions. The optimal length of monitoring with CVEEG during TH is unknown. The goal of the study was to determine the optimal duration of CVEEG monitoring to detect new-onset seizure activity and abnormal background patterns in patients with HIE undergoing whole-body hypothermia.Methods: This was a retrospective study conducted at Children’s Hospital of Buffalo. Term and late-preterm infants with moderate to severe HIE who underwent TH between May 2010 and May 2014 were selected. Infants were cooled to a core temperature of 33.5°C for 72h followed by slow rewarming over 6 hours. Most patients underwent a 30 min EEG prior to cooling and all were connected to CVEEG for the duration of TH and rewarming. Clinical and electrographic seizures were treated with antiepileptic drugs. The following data was collected: postmenstrual age, birth weight, gender, Apgar score, severity of HIE and presence of clinical and/or EEG seizures. EEG data included: normal background, excessive discontinuity, background suppression, burst suppression, sharp waves, excessive low voltage, and EEG seizure. EEG reports were collected from baseline EEG, and CVEEG at 24, 48 and 72h and during the rewarming period.Results: A total of 35 newborns that underwent TH for HIE and CVEEG were included. The seizure and no seizure groups were comparable in terms of gender, gestational age, Apgar scores and severity of HIE. Seizures with EEG ictal changes were seen in 9 patients (25.7%) within 72h. Time of seizure onset was within 30 min of initial EEG in 6 (17%), within 24 hours in 2 (6%), and during rewarming in one patient (3%). No new onset seizures were recorded between 24 to 72h prior to rewarming. There was a significant decrease in the frequency of seizures by 24-72h after the initiation of antiepileptic drugs (p= 0.04, McNemar’s test) in comparison to EEG obtained during the 0-24h period. Two neonates had clinical events between 24-48h without EEG correlation. One patient continued to have seizures despite anti-epileptic drugs. Background suppression was detected in 14 (40%) by 24h. The prevalence of excessive discontinuity, burst suppression, sharp wave and excessive low voltage on EEG did not significantly change after the initial 24h.Conclusions: In neonates with HIE undergoing TH, CVEEG has highest diagnostic yield within the first 24h and during the rewarming phase. Limiting CVEEG to the first 24h and during the rewarming phase in infants without seizures may reduce cost, prevent possible skin lesions and provide timely access to neuroimaging.