Bispectral EEG Index Monitoring of High-Dose Nitrous Oxide

This study sought to characterize the effects of 3070% nitrous oxide and 0.2-0.8% sevoflurane conscious sedation on quantitative electroencephalographic (EEG) readings as measured by the bispectral index (BIS). BIS is a processed parameter (algorithm) made available in 1997 by Aspect Medical Systems (Newton, Mass). As depicted in Figure 1, it is specifically designed to correlate a 1-100 numerical output with the level of hypnosis, amnesia, and sedation induced by a wide va­riety of agents. This study also attempted to verify the results of 2 previously published BIS/N₂0 investigations to confirm the clinical effects of high-dose (5070%) N₂0 and low-dose (0.4-0.8%) sevoflurane sedation and to establish whether BIS is a suitable monitor for either or both gases.

Figure 1. BIS range guidelines.
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