Abstracts

Rationale: SIRPIDs were defined by Hirsch et al. in 2004 as “periodic, rhythmic or ictal appearing discharges consistently induced by alerting stimuli and patient care activities”. Knowledge about relationships between SIRPID pattern and underlying type of brain injury and clinical outcomes is not yet fully understood. This study is an epidemiological survey of this intriguing electroencephalographic (EEG) pattern in critically ill patients of a general public hospital in Southern Brazil. Methods: We recorded routine EEGs in adult and child ICUs of the Hospital de Clínicas de Porto Alegre between March 2013 and May 2017. Our protocol consists of recording of 1 hour in digital EEG machine, using the 10-20 International System for electrode placement. Tactile (sternal rub), auditory (clapping, calling by name), painful (nipple pinching), and visual (passive ocular opening) stimuli were applied in the end. Traces were read by two electroencephalographers. A general description of the background activity was performed, and after a consensus, stimulus-induced events were classified as SIRPIDs or not. Results: We studied 416 EEGs, 28 of these presenting SIRPIDs (6.7%). Patients with SIRPIDs were 8-88 years old (mean: 59.3), 11 males (31.3%) and 17 females (60.7%). They spent 4 times higher days in ICU than patients without this finding (31.7 versus 7.6). Mortality rate for SIRPIDs patients was more than 2 times higher (67.9% versus 30.6%). Clinical pictures of these patients are showed in Table 1. Coma / stupor were present in 18/28 cases (64.3 %). Epileptic seizures occurred during the evolution in 21/28 cases (75 % - Table 2). Twenty patients (71.4%) were receiving cefepime or meropenem at the time of EEG recording. The most frequent EEG background activity was diffuse theta/delta rhythm (22/28 – 78.6%), and focal or multifocal interictal epileptiform discharges were found in 17 patients with SIRPIDs (60.7%). Types of SIRPIDs are shown in Table 3. SIRPIDs were more frequently produced  by tactile (11/28, 39.3%) and auditory stimuli (12/28, 42.9%). Conclusions: We found a high prevalence of SIRPIDs in critically ill patients, although at rates somewhat lower than those found in the literature, perhaps because of the duration of our recordings. SIRPIDs can be found in individuals of all ages, although it is more prevalent in mature adults (around 60 years of age). Patients with SIRPIDs have higher mortality rates and ICU stay rate two to four times higher, indicating a worse prognosis, which is not explained by their underlying pathology, since the diseases are the same as those of a general ICU. There is a strong association of SIRPIDs with decreased consciousness and with epileptic seizures in the clinical setting of these patients. We were not able to find correlations between the various types of SIRPIDs found, as well as the type of stimulus that elicited them, with evolution and prognosis due to the low sample number. The correlation of SIRPIDs with the use of antibiotics associated with epileptogenic encephalopathies, such as cefepime and meropenem, although plausible, needs to be better studied. SIRPIDs represent a special type of EEG response to extrinsic stimulation, indicating a state of increased cortical hyperexcitability. It is important to differentiate them from a normal EEG response to stimulation (a phenomenon that, on the contrary, gives a better prognosis to the patient). We advocate continuous EEG monitoring of all patients presenting SIRPIDs in a routine EEG recording, due to the high correlation of this finding with epileptic seizures. Funding: No funding received.