Abstracts

Rationale: EEG monitoring in critically ill patients is becoming more common with increased availability of portable electrographic monitoring devices. The clinical and prognostic implications of stimulus-induced rhythmic, periodic or ictal discharges (SIRPIDs) sometimes found on these recordings is uncertain.Methods: Consecutive adult patients hospitalized in an intensive care unit who underwent EEG recordings at three separate centers were included. Demographic data, including admission diagnosis, age, gender, history of epilepsy, and findings on the EEG recordings - including the presence of SIRPIDs (as defined by Hirsh et al., 2004), epileptiform discharges, background activity and overall reactivity - were noted. Characteristics of SIRPIDs, if present, were documented. Data were evaluated for clinical or electrographic predictors of development of SIRPIDs and for in-hospital mortality.Results: 416 patients were included in this study, of which 252 (60.6%) were male. The median age was 60.0 years (IQR 46.0, 71.0). SIRPIDs were identified in 43 patients (10.3%) and 104 (25%) did not survive to hospital dismissal. Among the three study sites, the proportion of patients with SIRPIDs was not significantly different (p=0.3351). On univariate analysis, patients with SIRPIDs were significantly older (64.0 years (IQR 52.0, 78.0) vs 59.0 years (IQR 45.0, 70.0), p=0.0286), more likely to be receiving antiepileptic medications at the time of the EEG recording (p=0.0003), and also to have epileptiform discharges (p=<0.0001), electrographic seizures (p=0.0001), and periodic epileptiform discharges apart from stimulation (p=0.0002). Patients who were older (63.5 years (55.0, 76.0) vs 58.0 years (43.0, 69.0), p=0.0011), suffered an anoxic event (p=<0.0001), had SIRPIDs (p=0.0143), did not have a history of epilepsy (p=0.0393), and lacked EEG reactivity (p=<0.0001) were more likely to die in hospital. However, on multivariate analysis, only older age (p=0.0050, OR 1.022, 95% CI 1.007-1.038), anoxia (p=<0.0001, OR 3.493, 95% CI 1.965-6.210) and absence of EEG reactivity (p<0.0001, OR 8.143, 95% CI 4.198, 15.795) remained significant.Conclusions: In critically ill patients undergoing EEG, SIRPIDs occurred in 10% and were associated with other electrographic abnormalities previously reported to indicate poor prognosis. SIRPIDs, however, were not independently associated with in-hospital mortality, as opposed to older age, anoxic insult and absence of EEG reactivity.