Sensitivity of Continuous Electroencephalography to Detect Ictal Activity After Cardiac Arrest

Importance Epileptiform electroencephalographic (EEG) patterns are common after resuscitation from cardiac arrest, are associated with patient outcome, and may require treatment. It is unknown whether continuous EEG monitoring is needed to detect these patterns or if brief intermittent monitoring is sufficient. If continuous monitoring is required, the necessary duration of observation is unknown. Objective To quantify the time-dependent sensitivity of continuous EEG for epileptiform event detection, and to compare continuous EEG to several alternative EEG-monitoring strategies for post-cardiac arrest outcome prediction. Design, Setting, and Participants This observational cohort study was conducted in 2 academic medical centers between September 2010 and January 2018. Participants included 759 adults who were comatose after being resuscitated from cardiac arrest and who underwent 24 hours or more of EEG monitoring. Main Outcomes and Measures Epileptiform EEG patterns associated with neurological outcome at hospital discharge, such as seizures likely to cause secondary injury. Results Overall, 759 patients were included in the analysis; 281 (37.0%) were female, and the mean (SD) age was 58 (17) years. Epileptiform EEG activity was observed in 414 participants (54.5%), of whom only 26 (3.4%) developed potentially treatable seizures. Brief intermittent EEG had an estimated 66% (95% CI, 62%-69%) to 68% (95% CI, 66%-70%) sensitivity for detection of prognostic epileptiform events. Depending on initial continuity of the EEG background, 0 to 51 hours of monitoring were needed to achieve 95% sensitivity for the detection of prognostic epileptiform events. Brief intermittent EEG had a sensitivity of 7% (95% CI, 4%-12%) to 8% (95% CI, 4%-12%) for the detection of potentially treatable seizures, and 0 to 53 hours of continuous monitoring were needed to achieve 95% sensitivity for the detection of potentially treatable seizures. Brief intermittent EEG results yielded similar information compared with continuous EEG results when added to multivariable models predicting neurological outcome. Conclusions and Relevance Compared with continuous EEG monitoring, brief intermittent monitoring was insensitive for detection of epileptiform events. Monitoring EEG results significantly improved multimodality prediction of neurological outcome, but continuous monitoring appeared to add little additional information compared with brief intermittent monitoring. This cohort study of patients resuscitated following cardiac arrest examines whether continuous monitoring of electroencephalographic activity improves detection of epileptiform events associated with neurological outcome and potentially treatable seizures. Question Does continuous electroencephalographic (EEG) monitoring improve detection of epileptiform events associated with neurological outcome or potentially treatable seizure among patients resuscitated from cardiac arrest compared with brief intermittent EEG? Findings In this cohort study including 759 patients who were resuscitated from cardiac arrest, continuous monitoring for nearly 48 hours was needed to achieve 95% sensitivity for prognostic epileptiform events; compared with brief intermittent EEG, continuous monitoring did not improve prediction of outcome at hospital discharge. Potentially treatable seizures were uncommon and rarely detected by brief intermittent monitoring. Meaning Compared with continuous EEG, brief intermittent EEG is insensitive for detection of potentially treatable seizures after cardiac arrest but may be sufficient to guide multimodality prediction of outcome at hospital discharge.