Abstracts

Rationale: Prolonged EEG monitoring in the ICU is now common. Studies suggest that the prevalence of nonconvulsive status epilepticus (NCSE) is 10%. Isolated seizures may be more common. Despite this, the selection criteria for monitoring remain ambiguous, and the impact of prolonged EEG monitoring on treatment is unclear. We addressed these questions by doing prolonged EEG on patients for whom a routine or prolonged EEG was requested by ICU staff. Methods: During a prospective but not randomized 22-month study, 130 ICU patients for whom staff requested an EEG were placed in 3 groups. One group received a 30-minute EEG. A second group, for whom staff requested a 30-minute EEG, instead got 16-24 hours of continuous video-EEG. The third group comprised patients for whom long-term video-EEG monitoring was requested to monitor suspected status epilepticus. Epileptologists compared the first 30 minutes of EEG with the subsequent recording to see if any additional information was obtained, and if it impacted treatment. Results: 34 patients had a routine 30-minute EEG. 1 was normal, 27 were slow or poorly reactive, and 6 (18%) showed epileptiform activity, including one with electrographic seizures. 83 patients, who might have received only a 30 minute EEG, were monitored with video-EEG for 16-24 hours. These included patients with trauma (2), tumor (7), stroke (7), metabolic derangement (16), cerebral hemorrhage (22), and hypoxic-ischemic injury (29). All EEGs were abnormal with slowing and poor reactivity. 28/83 patients (34%) showed epileptiform findings in the first 30 minutes, including periodic epileptiform discharges (PEDs), generalized or focal epileptiform discharges, burst suppression, triphasic waves, and 2 patients with clinical seizures. 5/28 developed additional epileptiform changes overnight, including 2 with clinical seizures, and in 4 treatment was changed. 55/83 patients (66%) had no epileptiform findings in the first 30 minutes, but 7/55 developed these overnight, including 2 with electrographic and 1 with clinical seizures. In 3 patients treatment was changed. Overall, in 7/83 patients treatment was changed based on prolonged as opposed to routine EEG, and 3 showed improvement. 13 patients known to have epilepsy, who presented with seizures, were deliberately placed on long term video-EEG monitor. 9/13 (69%) showed epileptiform abnormalities in the first 30 minutes including 3 with NCSE and 1 with focal seizures. Overnight 2 more evolved into NCSE, and prolonged EEG influenced therapy in 6/13. Conclusions: In 83 unselected ICU patients, overnight video-EEG, as opposed to a 30-minute EEG, detected additional epileptiform abnormalities in only 12 patients, and only 2 of those had clinically undetectable seizures. Only 7/83 patients (8%) had changes in treatment based on EEG findings. In contrast, patients with epilepsy who presented with seizures were more likely to have NCSE, and EEG guided treatment in 6/13 (46%). This study suggests that long-term EEG monitoring in an unselected ICU population has little benefit. In a selected population the benefit may be larger.