Abstracts

Rationale: Critically ill patients often have altered mental status of unclear etiology, and multiple studies have shown that a significant proportion of these patients are having electrographic seizures. Continuous EEG monitoring has been increasingly used to evaluate for these seizures, but our ability to select the appropriate patients to monitor is limited. We aim to study the incidence of seizures in the critical care setting and to evaluate for clinical predictors to improve the efficiency of continuous EEG monitoring.Methods: We retrospectively reviewed the EEG and clinical data on 1,123 consecutive patients who had continuous video EEG at the Cleveland Clinic between January 1, 2009 and December 31, 2010 using EEG data files, our epilepsy database (Ebase) and the electronic medical records. EEG seizures (with or without direct clinical correlates) were defined as evolving rhythms in frequency, distribution and/or morphology at 2 Hz or greater for more than 10 seconds duration. Results: EEG seizures were recorded in 215 patients on continuous EEG monitoring (19.1 %): 92% of these seizures occurred without clinical signs. State of consciousness predicted the incidence of seizures on continuous EEG with awake patients having 6%, lethargic patients exhibiting 20%, stuporous patients having 25% and comatose patients having 33% EEG seizures. The incidence of seizures was overrepresented in patients with intracranial tumors (40%), CNS infections (29%), subdural hemorrhage (29%), stroke (28%), and subcortical ICH (26%). When present, EEG seizures were detected within 24 hours in 90% of patients monitored, regardless of mental status. Conclusions: Our review of a large series of patients who underwent continuous EEG monitoring in the critical care setting demonstrates a linear increase in seizure incidence with declining mental status. We also describe a number of clinical conditions that are associated with a high incidence of EEG seizures. Our results may help in the appropriate selection of critical care patients for continuous EEG monitoring.