Emergent EEG in the emergency department in patients with altered mental states.

OBJECTIVE

To evaluate whether EEG performed within 30 min of referral by an ED physician helps establish diagnosis and/or changes management and in which clinical setting.

METHODS

Single-center prospective cohort intervention study 1 day/week, of sequentially referred adult patients with clinical seizures or altered mental status (AMS). Standard EEGs were performed by an EEG technician using a commercially available cap, interpreted by an epileptologist, immediately reported to the ED physician and a utility survey completed. Quality and interpretation of 20 min EEGs was compared to pre-specified 5 min segments of each EEG using the kappa coefficient.

RESULTS

Over 1 year, 82 patients underwent ED EEG. Tonic clonic seizure activity had occurred in 33%. Mean time for EEG setup was 13.1 ± 6.2 min. EEG assisted the diagnosis in 51%, changed ED management in 4% and would be ordered again if EEG was available in 46%. Positive utility of EEG was significantly associated with toxicologic, psychiatric and endocrine/metabolic causes of AMS vs. other causes (p<0.001) and sudden onset AMS (p=0.007). Independent predictors of whether ED EEG would be ordered if available were witnessed seizures (p=0.01), no prior head trauma (p=0.001) and survey respondent being a physician assistant (vs. MD) (p=0.02). The 5 (vs. 20) min EEG presented good agreement on waveform shape/amplitude (kappa=0.78), artifact (kappa=0.75) and interpretation categories (all kappa levels ≥ 0.70).

CONCLUSIONS

Rapid availability of standard full-montage EEG in the ED is feasible and helps establish a diagnosis in about half of AMS patients, but rarely changes management. An abbreviated 5 min full-montage EEG presents adequate reliability which may improve use in the ED.

SIGNIFICANCE

Specific presentations of AMS offer the best diagnostic benefit for EEG in the ED.