Associated factors and prognostic implications of stimulus-induced rhythmic, periodic, or ictal discharges

Importance: The implications of stimulus-induced rhythmic, periodic, or ictal discharges (SIRPIDs) sometimes found on prolonged electroencephalographic (EEG) recordings are uncertain. Objective: To evaluate the incidence of SIRPIDs and their clinical implications in critically ill patients. Design, Setting, and Participants: A multicenter, international retrospective studywas performed from October 1, 2012, through September 30, 2014, of consecutive adult patients hospitalized in intensive care units with alteration of consciousness who underwent EEG recordings at 3 separate centers. Demographic data, including admission diagnosis, age, sex, history of epilepsy, and EEG findings, were noted. Characteristics of SIRPIDs were documented. Data were evaluated for predictors of SIRPIDs and in-hospital mortality. Data analysis was performed from January 16, 2015, to June 15, 2015. Main Outcomes and Measures: Incidence of SIRPIDs, association of SIRPIDs with mortality and other EEG characteristics, and EEG and clinical predictors of mortality. Results: A total of 416 patients were studied. The median age of patients was 60 years (interquartile range, 46-71 years), and 252 (60.6%) were male. A total of 104 patients (25.0%) did not survive to hospital discharge. SIRPIDs were identified in 43 patients (10.3%). The proportion of patients with SIRPIDs was not significantly different across the 3 sites (P = .34). Anoxic brain injury (odds ratio [OR], 3.80; 95%CI, 1.73-8.33; P < .001), the use of antiepileptic medications (OR, 3.24; 95%CI, 1.31-8.00; P = .01), electrographic seizures (OR, 2.85; 95%CI, 1.13-7.19; P = .03), generalized periodic discharges with triphasic morphologic features (OR, 3.66; 95%CI, 1.67-8.02; P = .001), and sporadic sharp waves and periodic discharges (OR, 2.59; 95%CI, 1.13-5.92; P = .02) were independently associated with the presence of SIRPIDs. Older age (OR, 1.02; 95%CI, 1.01-1.04; P = .005), anoxic brain injury (OR, 3.49; 95%CI, 1.96-6.21; P ≤ .001), and absence of EEG reactivity (OR, 8.14; 95%CI, 4.20-15.79; P < .001) but not SIRPIDs (OR, 1.73; 95%CI, 0.79-3.78; P = .17) were independently associated with in-hospital mortality. Conclusions and Relevance: In critically ill patients undergoing EEG recordings, SIRPIDs occurred in 43 (10.3%) and were associated with other electrographic abnormalities previously reported to indicate poor prognosis. However, SIRPIDs were not independently associated with in-hospital mortality.