Effect of Nitrous Oxide Concentration on Event-related

Abstract

Effects of inhaling 3 levels of N2O:O2 on event-related brain potentials (ERP) and pain report were examined in 10 volunteers undergoing painful electrical stimulation of tooth pulp. A dose-response relationship was demonstrated between increasing concentrations of N2O in O2 and measures of ERP amplitude and pain report. Subjects inhaled room air, N2O 25, 37 and 50% in O2 while ERPs were recorded and pain reports were given. The procedure was repeated on 3 separate days with each subject experiencing all levels of treatment on each day. Analyses of variance revealed that both ERP amplitude and pain report significantly decreased as dosage increased, and a significant linear trend was observed for the positive-going ERP waveform deflection from 160-240 ms. Pain report scores decreased significantly (P < 0.001) and proportionally as dosage increased, but there was not a significant linear trend. Inhalation of N2O in O2 increased peak latency for the negative component at 50 ms and the positive component at 90 ms, but not for later components. These outcomes demonstrate that amplitude measures of the vertex ERP obtained with dental dolorimetry correlate consistently with pain and analgesia. Simultaneous assessment of brain electrical activity and subjective report appears to be a useful approach for the assessment of analgesia in humans.