BIS and spectral entropy monitoring during sedation with midazolam/remifentanil and dexmedetomidine/remifentanil

Haenggi and colleagues report considerable intra- and inter-individual variability in derived electroencephalogram (EEG) parameters (Bispectral Index (BIS), response entropy and state entropy) recorded in volunteers sedated with midazolam or dexmedetomidine infusions titrated to modified Ramsay scores of 2, 3 and 4, and a remifentanil infusion at a fixed target concentration. Possible explanations for the low, variable and fluctuating EEG parameters are that volunteers were intermittently asleep, and that remifentanil gave rise to a low amplitude, slowed EEG pattern despite maintained consciousness. BIS and entropy values should be interpreted in combination with clinical findings in patients sedated with these agents.