Nonlinear analysis of EEG in septic encephalopathy

Abstract

Electroencephalograms (EEe) were recorded in fourteen patients who experienced a severe septic encephalopathy (Sf). fEe analysis included visual inspection, spectral analysis and a recently developed nonlinear analysis (the Kaplan test). All fEes showed decreased fast activity and an increase ofslow wave activity on visual inspection. There was a nonsignificant trend of negative correlation between the spectral EEe analysis and the severity ofthe acute systemic illness (based on the sum score of 14 variables known as APACHE II score) (standard coefficient= -0.43, p 0.118). However, a much more pronounced and significant negative correlation was observed between the Kaplan test and the APACHE II score (standard coefficient= -0.94,' p = 0.005). The fEe abnormalities seen in these patients were independent of the sedation level. Neither the fEe parameters, nor the APACHE II score, predicted outcome. Nonlinear analysis is more powerful than spectral analysis to extract clinical relevant information from fEes in patients who experience a severe SEe The nonlinear EEG analysis suggest that brain dynamics in SE may be characterized by a shift into a fundamentally different level of cortical information exchange which can be summarized in nonlinear terminology as a loss of deterministic structure in the fEG. [Neural Res 1998; 20: 100–106]