To evaluate the discriminative power of BIS monitoring to classify the degree of mental state associated with the PCT graded sepsis cascade, and to assess its utility for monitoring the improvement or deterioration of sepsis. The primary endpoint of our study was to use an artefact-free 10-min mean BIS value to classify the degree of sepsis. As secondary endpoints, we correlated the mean BIS value to various mental state and sepsis parameters; PCT, C-reactive protein (CRP), Glasgow coma scale, and sequential organ failure assessment (SOFA) score. In a longitudinal study, patients' PCT sepsis grades were reassessed at a later time point and a second artefact-free 10-min mean BIS value was recorded to evaluate BIS evolution within the same patient.