Abstracts

Rationale: Electroenecephalography (EEG) has a central role in outcome prediction after anoxic/hypoxic encephalopathy following a cardiac arrest (CA). Indeed, it allows a non-invasive assessment of brain function and a quantification of the extent of neurological damage, and as well as the identification of non-convulsive status epilepticus. Continuous EEG monitoring (cEEG) has been consistently developed and studied; however, its value as compared to repeated standard EEG (sEEG) is unknown. In view of these practical aspects, especially in the many centers with limited EEG resources, this issue is of broad interest.Methods: We studied a prospective cohort of comatose adults treated with therapeutic hypothermia (TH) after a CA. cEEG data regarding background activity and epileptiform components were compared to two 20 minutes sEEG extracted from the cEEG recording (one during TH, and one in early normothermia, both including background reactivity testing).Results: 34 recordings were studied. During TH, the concordance between cEEG and sEEG was 97.1% (95% CI: 84.6 99.9%) for background discontinuity and reactivity evaluation, while it was 94.1% (95% CI 80.3 99.2%) regarding epileptiform activity. In early normothermia, we did not found any discrepancies. Perfect concordance at both time-points was obtained in 31/34 patients (91.2%; 95% CI: 76.3 98.1%). The median time between CA and the first EEG reactivity testing was 17.75 h (range: 4.75 25) for patients with perfect concordance and 10 h (range: 5.75 10.5) for the three patients in whom discordant findings between sEEG and cEEG were found (p=0.02, Wilcoxon rank-sum test).Conclusions: Standard EEGs with background reactivity evaluation performed at two separate time points, during therapeutic hypothermia and in normothermic conditions, seem to be as efficient as continuous EEG monitoring in the setting of coma after CA. However, in order to optimize the performance of this approach, it seems reasonable that the first EEG during hypothermia has to be performed after at least 12 hours after CA. These findings are novel and have in our view an important implication in clinical practice, particularly for centers managing these patients without resources to provide cEEG to every subject. While cEEG represents the investigation of choice in case of seizures or status epilepticus identification, particularly in normothermia, and is of invaluable utility in order to understand the complex and dynamic process of brain anoxia, the current study offers practical data to optimize the yield of EEG recordings in patients suffering from this dramatic neurologic condition.