NONLINEAR-ANALYSIS OF EEG IN SEPTIC ENCEPHALOPATHY

Electroencephalograms (EEG) were recorded in fourteen patients who exp erienced a severe septic encephalopathy (SE). EEG analysis included vi sual inspection, spectral analysis and a recently developed nonlinear analysis (the Kaplan test). All EEGs showed decreased fast activity an d an increase of slow wave activity on visual inspection. There was a nonsignificant trend of negative correlation between the spectral EEG analysis and the severity of the acute systemic illness (based on the sum score of 14 variables known as APACHE II score) (standard coeffici ent = -0.43, p = 0.118). However, a much more pronounced and significa nt negative correlation was observed between the Kaplan test and the A PACHE II score (standard coefficient = -0.94, p = 0.005). The EEG abno rmalities seen in these patients were independent of the sedation leve l. Neither the EEG parameters, nor the APACHE II score, predicted outc ome. Nonlinear analysis is more powerful than spectral analysis to ext ract clinical relevant information from EEGs in patients who experienc e a severe SE. The nonlinear EEG analysis suggest that brain dynamics in SE may be characterized by a shift into a fundamentally different l evel of cortical information exchange which can be summarized in nonli near terminology as a loss of deterministic structure in the EEG.