The effects of 30% nitrous oxide on auditory evoked middle latency responses

The effects of 30% nitrous oxide on auditory evoked middle latency responses (MLR) were studied in 11 healthy volunteers. The evoked potentials were averaged from electroencephalograms following stimulation by 2048 clicks at 10 Hz and of 0.5 ms duration. Latencies and amplitudes of the Pa-Nb wave were measured and compared with the control values. The mean amplitude after inhalation of nitrous oxide for 30 minutes nitrous oxide was 54.2 +/- 23.9 (SD) % of control value. This decrease was recognised as statistically significant (P less than 0.05). Latencies of the Pa-Nb wave did not alter during the inhalation of nitrous oxide. The results show that 30% nitrous oxide slightly suppressed the auditory cortex.