A Bispectral EEG Device and Standard Deviation Filtering Can Capture Delirium Severity and Predict Mortality

Background: Delirium has been a social burden among elderly inpatients due to the significantly poor outcomes related to it (Inouye, 2014). Delirium is difficult to diagnose, and often goes untreated (Ely, 2004). We have developed the bispectral electroencephalography (BSEEG) method for detection of delirium and prediction of poor outcomes. This study aimed to improve the BSEEG method by introducing a new thumb-size EEG device.

Method: This is a prospective cohort study. EEG data was obtained and BSEEG score was calculated. BSEEG scores were filtered based on standard deviation (SD) values to exclude signals with high noise. Non-filtered and SD-filtered BSEEG scores were analyzed. BSEEG scores were compared to the results of each delirium screening scale. Additionally, the 365-day mortalities and length of stay (LOS) in the hospital were analyzed. The protocol of this study was approved by the University of Iowa Institutional Review Board.

Results: 279 elderly subjects were enrolled and 620 BSEEG recordings were obtained. 142 subjects were categorized as BSEEG-positive, reflecting slower EEG activity. BSEEG scores were higher in the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU)-positive group than in the CAM-ICU-negative group (p< 0.001). There were significant correlations between BSEEG scores and Delirium Rating Scale-Revised-98 (DRS) and Delirium Observation Screening Scale (DOSS) scores (p< 0.001). The mortality rate of the BSEEG-positive group was significantly higher than that of the BSEEG-negative group (22.6% vs 9.1%, p=0.004). The LOS of the BSEEG-positive group was longer than the BSEEG-negative group (median LOS: 7 vs 4 days, p = 0.032). BSEEG score after SD filtering showed stronger correlations between BSEEG score and delirium screening score, and more significant prediction of mortality.

Discussion: It was previously demonstrated that BSEEG can differentiate between delirium positive and negative cases (Shinozaki, 2018). In this study, BSEEG score differentiated between CAM-ICU positive and negative groups as expected. BSEEG correlation with DRS and DOSS scores suggests BSEEG score can reflect the presence and severity of delirium. BSEEG score correlation with mortality and LOS also replicates previous findings (Shinozaki, 2019).

Conclusions: We confirmed usefulness of BSEEG method for detection of delirium, quantitation of delirium severity, and prediction of patient outcomes with a new thumb-size EEG device.

References:

E. W. Ely et al., Current opinions regarding the importance, diagnosis, and management of delirium in the intensive care unit. Crit. Care Med. 32, 106-112 (2004).

G. Shinozaki et al., Delirium detection by a novel bispectral electroencephalography device in general hospital. Psychiatry Clin. Neurosci. 72, 856-863 (2018).

G. Shinozaki et al., Identification of Patients With High Mortality Risk and Prediction of Outcomes in Delirium by Bispectral EEG. J. Clin. Psychiatry 80, (2019).

S. K. Inouye et al., Delirium in elderly people. Lancet 383, 911-922 (2014).