Effects of nitrous oxide sedation on resting electroencephalogram topography

To quantify the effects of nitrous oxide (N(2)O) gas on electroencephalogram (EEG) topography in healthy male participants.

Healthy male participants were administered 20% (n=8) or 40% (n=8) N(2)O while having high-density (modified 10-20) noise minimized EEG recordings.

Nitrous oxide was found to produce clear reductions in resting total power, particularly at frontal-vertex sites. These reductions were found to principally reflect reductions in band-limited delta power. Following the termination of N(2)O inhalation, during N(2)O washout, selective increases in frontal theta power were observed that increased above baseline values.

Nitrous oxide does not produce the classical anteriorization of slow wave activity typically seen during anesthetic induction. Instead N(2)O reduces frontal slow wave (delta) activity, which during gas washout produces a withdrawal response of enhanced frontal slow wave (theta) activity.

Attempts to characterize a unitary mechanism of loss of consciousness during anesthesia on the basis of the topographic electroencephalographic changes is challenged by the distinct EEG effects that N(2)O has when compared to other well known anesthetic agents that include propofol and sevoflurane.